Sample &
Buy
Product
Folder
Support &
Community
Tools &
Software
Technical
Documents
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
LM5035 PWM Controller With Integrated Half-Bridge and SyncFET Drivers
1 Features
3 Description
•
•
The LM5035 half-bridge controller-gate driver
contains all of the features necessary to implement
half-bridge topology power converters using voltage
mode control with line voltage feedforward. The
floating high-side gate driver is capable of operating
with supply voltages up to 105 V. Both the high-side
and low-side gate drivers are capable of 2-A peak. An
internal high voltage start-up regulator is included,
along with programmable line undervoltage lockout
(UVLO) and overvoltage protection (OVP). The
oscillator is programmed with a single resistor to
frequencies up to 2 MHz. The oscillator can also be
synchronized to an external clock. A current sense
input and a programmable timer provide cycle-bycycle current limit and adjustable hiccup mode
overload protection.
1
•
•
•
•
•
•
•
•
•
•
•
•
105-V, 2-A Half-Bridge Gate Drivers
Synchronous Rectifier-Control Outputs With
Programmable Delays
High-Voltage (105-V) Start-up Regulator
Voltage Mode Control With Line Feedforward and
Volt-Second Limiting
Resistor Programmed, 2-MHz Capable Oscillator
Patent Pending Oscillator Synchronization
Programmable Line Undervoltage Lockout
Line Overvoltage Protection
Internal Thermal Shutdown Protection
Adjustable Soft-Start
Versatile Dual Mode Overcurrent Protection With
Hiccup Delay Timer
Cycle-by-Cycle Overcurrent Protection
Direct Optocoupler Interface
5-V Reference Output
2 Applications
•
•
Device Information(1)
PART NUMBER
LM5035
PACKAGE
BODY SIZE (NOM)
HTSSOP
PowerPAD™ (20)
6.50 mm × 4.40 mm
WQFN (24)
5.00 mm × 4.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Industrial Power Converters
Telecom Power Converters
Simplied Application Diagram
VPWR
LM5035
VIN
HO
VOUT
UVLO
OVP
LO
RAMP
RT
SS
SR2
SR1
COMP
AGND
PGND
Error Amplifier
and Isolation
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
4
4
5
5
5
8
Absolute Maximum Ratings ......................................
ESD Ratings ............................................................
Recommended Operating Conditions.......................
Thermal Information .................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 10
7.1 Overview ................................................................. 10
7.2 Functional Block Diagram ....................................... 11
7.3 Feature Description................................................. 12
7.4 Device Functional Modes........................................ 19
8
Application and Implementation ........................ 20
8.1 Application Information............................................ 20
8.2 Typical Application ................................................. 20
9 Power Supply Recommendations...................... 31
10 Layout................................................................... 31
10.1 Layout Guidelines ................................................. 31
10.2 Layout Example .................................................... 32
11 Device and Documentation Support ................. 32
11.1
11.2
11.3
11.4
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
32
32
32
32
12 Mechanical, Packaging, and Orderable
Information ........................................................... 32
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision G (March 2013) to Revision H
Page
•
Added ESD Rating table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section. ................................................................................................ 1
•
Deleted Thermal Resistance section from Electrical Characteristics table. ........................................................................... 5
Changes from Revision F (March 2013) to Revision G
•
2
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 21
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
5 Pin Configuration and Functions
PWP Package
20-Pin HTSSOP With PowerPAD
Top View
OVP
3
18
SR1
4
17
SR2
5
16
VCC
COMP
RT
EP
AGND
6
CS
7
14
LO
SS
8
13
13
HO
DLY
9
12
HS
RES
10
11
HB
24
23
22
21
20
NC
1
19
REF
OVP
2
18
SR1
COMP
3
17
SR2
RT
4
16
VCC
AGND
5
15
PGND
CS
6
14
LO
SS
7
13
HO
PGND
15
NC
REF
EP
DLY
8
9
10
11
12
HS
19
VIN
2
HB
UVLO
NC
VIN
NC
20
RAMP
1
RES
RAMP
UVLO
NHZ Package
24-Pin WQFN
Top View
Pin Functions
PIN
NO.
TYPE
DESCRIPTION
APPLICATION INFORMATION
NAME
AGND
HTSSOP
WQFN
6
5
GND
Analog ground
Connect directly to Power Ground.
Input to the pulse width modulator
An external optocoupler connected to the COMP pin sources current into an
internal NPN current mirror. The PWM duty cycle is maximum with zero input
current, while 1mA reduces the duty cycle to zero. The current mirror improves
the frequency response by reducing the AC voltage across the optocoupler
detector.
COMP
4
3
I/O
CS
7
6
I
Current sense input for current limit
If CS exceeds 0.25 V, the output pulse will be terminated, entering cycle-bycycle current limit. An internal switch holds CS low for 50 ns after HO or LO
switches high to blank leading edge transients.
DLY
9
8
I
Timing programming pin for the LO and HO
to SR1 and SR2 outputs
An external resistor to ground sets the timing for the nonoverlap time of HO to
SR1 and LO to SR2.
HB
11
11
I/O
Boost voltage for the HO driver
An external diode is required from VCC to HB and an external capacitor is
required from HS to HB to power the HO gate driver.
HO
13
13
O
High side gate drive output
Output of the high side PWM gate driver. Capable of sinking 2-A peak current.
HS
12
12
I/O
Switch node
Connection common to the transformer and both power switches. Provides a
return path for the HO gate driver.
LO
14
NC
14
O
Low side gate drive output
Output of the low side PWM gate driver. Capable of sinking 2-A peak current.
1, 10, 20, 22
—
No connection
No electrical contact.
Line overvoltage protection
An external voltage divider from the power source sets the shutdown levels.
The threshold is 1.25 V. Hysteresis is set by an internal current source that
sources 23 µA into the external resistor divider.
Power ground
Connect directly to Analog Ground.
OVP
3
2
I
PGND
15
15
GND
RAMP
1
23
I
Modulator ramp signal
An external RC circuit from VIN sets the ramp slope. This pin is discharged at
the conclusion of every cycle by an internal FET. Discharge is initiated by either
the internal clock or the Volt Second clamp comparator.
REF
19
19
O
Output of 5-V reference
Maximum output current is 20 mA. Locally decoupled with a 0.1-µF capacitor.
RT
5
4
I
Oscillator frequency control and sync clock
input
Normally biased at 2 V. An external resistor connected between RT and AGND
sets the internal oscillator frequency. The internal oscillator can be
synchronized to an external clock with a frequency higher than the free running
frequency set by the RT resistor.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
3
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
Pin Functions (continued)
PIN
NO.
TYPE
DESCRIPTION
APPLICATION INFORMATION
NAME
HTSSOP
WQFN
RES
10
9
I
Restart timer
If cycle-by-cycle current limit is exceeded during any cycle, a 22-µA current is
sourced to the RES pin capacitor. If the RES capacitor voltage reaches 2.5 V,
the soft-start capacitor will be fully discharged and then released with a pull-up
current of 1.2 µA. After the first output pulse at LO (when SS > COMP offset,
typically 1 V), the SS pin charging current will revert to 55 µA.
SR1
18
18
O
Synchronous rectifier driver output
Control output of the synchronous FET gate. Capable of 0.5-A peak current.
SR2
17
17
O
Synchronous rectifier driver output
Control output of the synchronous FET gate. Capable of 0.5-A peak current.
SS
8
7
I
Soft-start input
An internal 55-µA current source charges an external capacitor to set the softstart rate. During a current limit restart sequence, the internal current source is
reduced to 1.2 µA to increase the delay before retry.
UVLO
2
24
I
Line undervoltage lockout
An external voltage divider from the power source sets the shutdown and
standby comparator levels. When UVLO reaches the 0.4-V threshold the VCC
and REF regulators are enabled. When UVLO reaches the 1.25-V threshold,
the SS pin is released and the device enters the active mode. Hysteresis is set
by an internal current sink that pulls 23 µA from the external resistor divider.
VCC
16
16
I/O
Output of the high voltage start-up regulator.
The VCC voltage is regulated to 7.6 V
If an auxiliary winding raises the voltage on this pin above the regulation setpoint, the start-up regulator will shutdown, thus reducing the internal power
dissipation.
VIN
20
21
I
Input voltage source
Input to the Start-up Regulator. Operating input range is 13 V to 100 V with
transient capability to 105 V. For power sources outside of this range, the
LM5035 can be biased directly at VCC by an external regulator.
Exposed pad, underside of package (WQFN)
EP
GND
PowerPAD (HTSSOP)
No electrical contact. Connect to system ground plane for reduced thermal
resistance.
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
MAX
UNIT
VIN to GND
–0.3
105
V
HS to GND
–1
105
V
HB to GND
–0.3
118
V
HB to HS
–0.3
18
V
VCC to GND
–0.3
16
V
CS, RT, DLY to GND
–0.3
5.5
V
10
mA
COMP input current
All other inputs to GND
–0.3
Junction temperature
Storage temperature, Tstg
(1)
(2)
–65
7
V
150
°C
150
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office or Distributors for availability and
specifications.
6.2 ESD Ratings
VALUE
V(ESD) (1)
(1)
(2)
(3)
4
Electrostatic
discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (2)
±1500
Charged-device model (CDM), per JEDEC specification JESD22C101 (3)
±1000
UNIT
V
The human body model is a 100-pF capacitor discharged through a 1.5-kΩ resistor into each pin. 2 kV for all pins except HB, HO, and
HS, which are rated at 1.5 kV.
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
(1)
MIN
VIN voltage
NOM
MAX
UNIT
V
13
105
External voltage applied to VCC
8
15
V
Operating Junction Temperature
–40
125
°C
(1)
Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which
operation of the device is intended to be functional. For ensured specifications and test conditions, see the Electrical Characteristics.
6.4 Thermal Information
LM5035
THERMAL METRIC (1)
PWP (HTSSOP)
NHZ (WQFN)
20 PINS
24 PINS
UNIT
RθJA
Junction-to-ambient thermal resistance
36.2
30
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
20.6
20.1
°C/W
RθJB
Junction-to-board thermal resistance
17.4
5.5
°C/W
ψJT
Junction-to-top characterization parameter
0.5
0.2
°C/W
ψJB
Junction-to-board characterization parameter
17.2
5.5
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
1.6
1.5
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
6.5 Electrical Characteristics
VVIN = 48 V, VVCC = 10 V externally applied, RRT = 15.0 kΩ, RDLY = 27.4 kΩ, VUVLO = 3 V, VOVP = 0 V unless otherwise
stated (1) (2).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
START-UP REGULATOR (VCC PIN)
VVCC
VCC voltage
IVCC = 10 mA
IVCC(LIM)
VCC current limit
VVCC = 7 V
VVCCUV
VCC undervoltage
threshold (VCC increasing)
VIN = VCC, ΔVVCC from
the regulation set point
VCC decreasing
VCC – PGND
Start-up regulator current
VIN = 90 V, UVLO = 0 V
Supply current into VCC
from external source
Outputs and COMP open,
VVCC = 10 V, outputs
switching
IVIN
TJ = 25°C
TJ = –40°C to 125°C
7.6
7.3
TJ = 25°C
TJ = –40°C to 125°C
25
0.1
TJ = –40°C to 125°C
V
0.2
TJ = 25°C
6.2
5.5
TJ = 25°C
6.9
30
TJ = –40°C to 125°C
70
TJ = 25°C
V
mA
20
TJ = 25°C
TJ = –40°C to 125°C
7.9
V
µA
4
TJ = –40°C to 125°C
6
mA
VOLTAGE REFERENCE REGULATOR (REF PIN)
VREF
(1)
(2)
TJ = 25°C
REF voltage
IREF = 0 mA
REF voltage regulation
IREF = 0 to 10 mA
REF current limit
REF = 4.5 V
TJ = –40°C to 125°C
5
4.85
TJ = 25°C
5.15
25
TJ = –40°C to 125°C
50
TJ = 25°C
TJ = –40°C to 125°C
20
15
V
mV
mA
All limits are ensured. All electrical characteristics having room temperature limits are tested during production with TA = 25°C. All hot
and cold limits are ensured by correlating the electrical characteristics to process and temperature variations and applying statistical
process control.
Typical specifications represent the most likely parametric norm at 25°C operation.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
5
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
Electrical Characteristics (continued)
VVIN = 48 V, VVCC = 10 V externally applied, RRT = 15.0 kΩ, RDLY = 27.4 kΩ, VUVLO = 3 V, VOVP = 0 V unless otherwise
stated(1)(2).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
UVLO AND SHUTDOWN (UVLO PIN)
TJ = 25°C
1.25
VUVLO
Undervoltage threshold
IUVLO
Hysteresis current
UVLO pin sinking
Undervoltage shutdown
threshold
UVLO voltage falling, TJ = 25°C
0.3
V
Undervoltage standby
enable threshold
UVLO voltage rising, TJ = 25°C
0.4
V
TJ = –40°C to 125°C
1.212
TJ = 25°C
1.288
23
TJ = –40°C to 125°C
19
27
V
µA
OVERVOLTAGE PROTECTION (OVP PIN)
VOVP
Overvoltage threshold
IOVP
Hysteresis current
TJ = 25°C
1.25
TJ = –40°C to 125°C
OVP pin sourcing
1.212
TJ = 25°C
1.288
23
TJ = –40°C to 125°C
19
27
V
µA
CURRENT SENSE INPUT (CS PIN)
VCS
Current limit threshold
CS delay to output
TJ = 25°C
0.25
TJ = –40°C to 125°C
0.228
TJ = 25°C, CS from zero to 1 V, Time for HO and LO to
fall to 90% of VCC Output load = 0 pF
Leading edge blanking time
TJ = 25°C
at CS
CS sink impedance
(clocked)
Internal FET sink
impedance
TJ = 25°C
0.272
V
80
ns
50
ns
32
TJ = –40°C to 125°C
60
Ω
CURRENT LIMIT RESTART (RES PIN)
VRES
RES threshold
TJ = 25°C
2.5
TJ = –40°C to 125°C
Charge source current
VRES = 1.5 V
Discharge sink current
VRES = 1 V
2.4
TJ = 25°C
2.6
22
TJ = –40°C to 125°C
16
TJ = 25°C
28
12
TJ = –40°C to 125°C
8
16
V
µA
µA
SOFT-START (SS PIN)
ISS
Charging current in normal
operation
VSS = 0
Charging current during a
hiccup mode restart
VSS = 0
Soft-stop current sink
VSS = 2.5 V
TJ = 25°C
55
TJ = –40°C to 125°C
40
TJ = 25°C
70
1.2
TJ = –40°C to 125°C
0.6
TJ = 25°C
1.8
55
TJ = –40°C to 125°C
40
70
µA
µA
µA
OSCILLATOR (RT PIN)
TJ = 25°C
185
TJ = –40°C to 125°C
180
200
FSW1
Frequency 1 (at HO, half
oscillator frequency)
RRT = 15 kΩ,
FSW2
Frequency 2 (at HO, half
oscillator frequency)
RRT = 5.49 kΩ
DC level
TJ = 25°C
2
TJ = 25°C
3
Input Sync threshold
6
TJ = 25°C
Submit Documentation Feedback
220
500
TJ = –40°C to 125°C
TJ = –40°C to 125°C
215
430
2.5
570
kHz
kHz
V
3.4
V
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Electrical Characteristics (continued)
VVIN = 48 V, VVCC = 10 V externally applied, RRT = 15.0 kΩ, RDLY = 27.4 kΩ, VUVLO = 3 V, VOVP = 0 V unless otherwise
stated(1)(2).
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
PWM CONTROLLER (COMP PIN)
Delay to output
VPWM-OS
SS to RAMP offset
TJ = 25°C
80
TJ = 25°C
1
TJ = –40°C to 125°C
0.7
Minimum duty cycle
SS = 0 V, TJ = 25°C
Small signal impedance
ICOMP = 600 µA, COMP current to PWM voltage,
TJ = 25°C
ns
1.2
V
0%
Ω
5000
MAIN OUTPUT DRIVERS (HO and LO PINS)
TJ = 25°C
0.25
Output high voltage
IOUT = 50 mA, VHB – VHO,
VVCC – VLO
Output low voltage
IOUT = 100 mA
Rise time
CLOAD = 1 nF, TJ = 25°C
15
ns
Fall time
CLOAD = 1 nF, TJ = 25°C
13
ns
Dead time, HO to LO, LO
to HO
VDLY = VREF, ICOMP = 0 mA
Peak source current
VHO,LO = 0 V, VVCC = 10 V , TJ = 25°C
1.25
A
Peak sink current
VHO,LO = 10 V, VVCC = 10 V, TJ = 25°C
2
A
TJ = –40°C to 125°C
TJ = 25°C
0.2
TJ = –40°C to 125°C
0.5
TJ = 25°C
TJ = –40°C to 125°C
V
0.5
70
45
100
V
ns
VOLTAGE FEEDFORWARD (RAMP PIN)
RAMP comparator
threshold
COMP current = 0
TJ = 25°C
2.5
2.6
V
TJ = –40°C to 125°C
2.4
Output high voltage
IOUT = 10 mA, VVCC – VSR1, TJ = 25°C
VVCC – VSR2
TJ = –40°C to 125°C
0.25
Output low voltage
IOUT = 20 mA (sink)
Rise time
CLOAD = 1 nF, TJ = 25°C
40
ns
Fall time
CLOAD = 1 nF, TJ = 25°C
20
ns
Peak source current
VSR = 0, VVCC = 10 V, TJ = 25°C
0.5
A
Peak sink current
VSR = VVCC, VVCC = 10 V, TJ = 25°C
0.5
A
RDLY = 10 kΩ, TJ = 25°C
40
SYNCHRONOUS RECTIFIER DRIVERS (SR1, SR2)
T1
Dead time, SR1 falling to
HO rising, SR2 falling to
LO rising
RDLY = 27.4 kΩ
0.1
TJ = 25°C
0.08
TJ = –40°C to 125°C
0.2
TJ = 25°C
TJ = –40°C to 125°C
100
75
RDLY = 100 kΩ, TJ = 25°C
T2
RDLY = 27.4 kΩ
125
V
ns
300
RDLY = 10 kΩ, TJ = 25°C
Dead time, HO falling to
SR1 rising, LO falling to
SR2 rising
V
20
TJ = 25°C
TJ = –40°C to 125°C
45
30
65
ns
RDLY = 100 kΩ, TJ = 25°C
140
Shutdown temperature
TJ = 25°C
165
°C
Hysteresis
TJ = 25°C
20
°C
THERMAL SHUTDOWN
TSD
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
7
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
6.6 Typical Characteristics
8
8
7
7
6
6
5
VREF
5
VVCC (V)
4
3
4
3
2
2
1
1
0
0
5
10
15
0
20
5
0
10
OSCILLATOR FREQUENCY (kHz)
4
VREF (V)
30
1000
5
3
2
1
900
800
700
600
500
400
300
200
100
0
0
0
5
10
15
20
25
0
10
20
IREF (mA)
Figure 3. VREF vs IREF
40
SOFT-START & STOP CURRENT (PA)
RRT = 15k
400
395
0
40
50
Figure 4. Frequency vs RT
60
405
390
-40
30
RRT (k:)
410
OSCILLATOR FREQUENCY (kHz)
25
Figure 2. VVCC vs IVCC
Figure 1. VVCC and VREF vs VVIN
6
80
120
30
58
29
SOFT-START
56
28
54
SOFT-STOP
27
52
26
50
25
48
24
46
23
44
22
RESTART
42
40
-40
TEMPERATURE (ºC)
21
20
0
40
80
120
TEMPERATURE (ºC)
Figure 5. Oscillator Frequency vs Temperature
8
20
15
IVCC (mA)
VVIN (V)
RESTART CURRENT (PA)
VVCC and VREF (V)
VVCC
Figure 6. Soft-Start and Stop Current vs Temperature
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Typical Characteristics (continued)
6500
350
5500
5000
4500
4000
-40
300
HO / LO TO SR DEADTIME (ns)
RESISTANCE (:)
6000
250
150
100
T2
50
0
0
40
80
T1
200
120
0
20
40
60
80
100
RDLY (k:)
TEMPERATURE (ºC)
Figure 7. Effective Comp Input Impedance
Figure 8. RDLY vs Dead Time
60
120
115
55
110
50
T2 (ns)
T1 (ns)
105
100
45
95
40
RDLY = 27.4 k:
90
RDLY = 27.4 k:
35
85
80
-40
0
40
80
30
-40
120
TEMPERATURE (ºC)
0
40
80
120
TEMPERATURE (oC)
Figure 9. SR T1 Parameter vs Temperature
Figure 10. SR T2 Parameter vs Temperature
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
9
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
7 Detailed Description
7.1 Overview
The LM5035 PWM controller contains all of the features necessary to implement half-bridge voltage-mode
controlled power converters. The LM5035 provides two gate driver outputs to directly drive the primary side
power MOSFETs and two signal level outputs to control secondary synchronous rectifiers through an isolation
interface. Secondary side drivers, such as the LM5110, are typically used to provide the necessary gate drive
current to control the sync MOSFETs. Synchronous rectification allows higher conversion efficiency and greater
power density than conventional PN or Schottky rectifier techniques. The LM5035 can be configured to operate
with bias voltages ranging from 8 V to 105 V. Additional features include line undervoltage lockout, cycle-by-cycle
current limit, voltage feedforward compensation, hiccup mode fault protection with adjustable delays, soft-start, a
2-MHz capable oscillator with synchronization capability, precision reference, thermal shutdown and
programmable volt-second clamping. These features simplify the design of voltage-mode half-bridge DC-DC
power converters. See the Functional Block Diagram.
10
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
7.2 Functional Block Diagram
7.6V SERIES
REGULATOR
VIN
SHUTDOWN
0.4V
UVLO
VCC
LOGIC
5V
Reference
UVLO-STANDBY
1.25V
REF
VCC/REF
UVLO
23 PA
THERMAL
LIMIT
(165ºC)
23 PA
+5V
OVP-STANDBY
OVP
HB
1.25V
HO
Q
CLK
RT/SYNC
DRIVER
T
OSCILLATOR
Timer
Q
SLOPE
PROPORTIONAL
TO VIN
S
HS
VCC
Q
R
RAMP
LO
DRIVER
FEED-FORWARD RAMP
REF
VCC
5k
SR1
PWM
COMP
1:1
1V
SS
VCC
LOGIC
SR2
SS Buffer
(Sink Only)
UVLOStandby
DLY
OVP-Standby
Shutdown
2.5V
MAX V*S
CLAMP
Soft-Start
Hiccup
2.5V
+5V
CS
D Q
0.25V
CLK
CLK + LEB
22 PA
CURRENT
LIMIT
CYCLE
RES
+5V
SS
SOFT-START
55 PA
RESTART DELAY
12 PA
NON-CURRENT
LIMIT CYCLE
1.2 PA
SS
PGND
55 PA
AGND
1 mA
SHUTDOWN
SOFT-STOP
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
11
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
7.3 Feature Description
7.3.1 High-Voltage Start-Up Regulator
The LM5035 contains an internal high voltage start-up regulator that allows the input pin (VIN) to be connected
directly to a nominal 48-V DC input voltage. The regulator input can withstand transients up to 105 V. The
regulator output at VCC (7.6-V) is internally current limited to 25-mA typical. When the UVLO pin potential is
greater than 0.4 V, the VCC regulator is enabled to charge an external capacitor connected to the VCC pin. The
VCC regulator provides power to the voltage reference (REF) and the output drivers (LO, SR1, and SR2). When
the voltage on the VCC pin exceeds the UVLO threshold of 7.6 V, the internal voltage reference (REF) reaches
its regulation set-point of 5 V and the UVLO voltage is greater than 1.25 V, the controller outputs are enabled.
The value of the VCC capacitor depends on the total system design, and its start-up characteristics. The
recommended range of values for the VCC capacitor is 0.1 µF to 100 µF.
The VCC undervoltage comparator threshold is lowered to 6.2-V (typical) after VCC reaches the regulation setpoint. If VCC falls below this value, the outputs are disabled, and the soft-start capacitor is discharged. If VCC
increases above 7.6 V, the outputs will be enabled and a soft-start sequence will commence.
The internal power dissipation of the LM5035 can be reduced by powering VCC from an external supply. In
typical applications, an auxiliary transformer winding is connected through a diode to the VCC pin. This winding
must raise the VCC voltage above 8.3 V to shut off the internal start-up regulator. Powering VCC from an
auxiliary winding improves efficiency while reducing the power dissipation of the controller. The undervoltage
comparator circuit will still function in this mode, requiring that VCC never falls below 6.2 V during the start-up
sequence.
During a fault mode, when the converter auxiliary winding is inactive, external current draw on the VCC line must
be limited such that the power dissipated in the start-up regulator does not exceed the maximum power
dissipation of the IC package.
An external DC bias voltage can be used instead of the internal regulator by connecting the external bias voltage
to both the VCC and the VIN pins. The external bias must be greater than 8.3 V to exceed the VCC UVLO
threshold and less than the VCC maximum operating voltage rating (15 V).
7.3.2 Line Undervoltage Detector
The LM5035 contains a dual level undervoltage Lockout (UVLO) circuit. When the UVLO pin voltage is below
0.4 V, the controller is in a low current shutdown mode. When the UVLO pin voltage is greater than 0.4 V but
less than 1.25 V, the controller is in standby mode. In standby mode, the VCC and REF bias regulators are
active while the controller outputs are disabled. When the VCC and REF outputs exceed the VCC and REF
undervoltage thresholds and the UVLO pin voltage is greater than 1.25 V, the outputs are enabled and normal
operation begins. An external set-point voltage divider from VIN to GND can be used to set the minimum
operating voltage of the converter. The divider must be designed such that the voltage at the UVLO pin will be
greater than 1.25 V when VIN enters the desired operating range. UVLO hysteresis is accomplished with an
internal 23-µA current sink that is switched on or off into the impedance of the set-point divider. When the UVLO
threshold is exceeded, the current sink is deactivated to quickly raise the voltage at the UVLO pin. When the
UVLO pin voltage falls below the 1.25-V threshold, the current sink is enabled causing the voltage at the UVLO
pin to quickly fall. The hysteresis of the 0.4-V shutdown comparator is internally fixed at 100 mV.
The UVLO pin can also be used to implement various remote enable and disable functions. Turning off a
converter by forcing the UVLO pin to the standby condition provides a controlled soft-stop. See the Soft-Start
section for more details.
7.3.3 Line Overvoltage, Load Overvoltage, Remote Thermal Protection
The LM5035 provides a multipurpose OVP pin that supports several fault protection functions. When the OVP pin
voltage exceeds 1.25 V, the controller is held in standby mode, which immediately halts the PWM pulses at the
HO and LO pins. In standby mode, the VCC and REF bias regulators are active while the controller outputs are
disabled. When the OVP pin voltage falls below the 1.25-V OVP threshold, the outputs are enabled and normal
soft-start sequence begins. Hysteresis is accomplished with an internal 23-µA current source that is switched on
or off into the impedance of the OVP pin set-point divider. When the OVP threshold is exceeded, the current
source is enabled to quickly raise the voltage at the OVP pin. When the OVP pin voltage falls below the 1.25-V
threshold, the current source is disabled causing the voltage at the OVP pin to quickly fall.
See the Application Information section for several examples of how to use the OVP pin.
12
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Feature Description (continued)
7.3.4 Reference
The REF pin is the output of a 5-V linear regulator that can be used to bias an optocoupler transistor and
external housekeeping circuits. The regulator output is internally current limited to 20-mA (typical).
7.3.5 Cycle-by-Cycle Current Limit
The CS pin is driven by a signal representative of the transformer primary current. If the voltage sensed at CS
pin exceeds 0.25 V, the current sense comparator terminates the HO or LO output driver pulse. If the highcurrent condition persists, the controller operates in a cycle-by-cycle current-limit mode with duty cycle
determined by the current sense comparator instead of the PWM comparator. Cycle-by-cycle current limiting may
trigger the hiccup mode restart cycle, depending on the configuration of the RES pin (see the Overload
Protection Timer section).
TI recommends placing a small R-C filter connected to the CS pin and located near the controller to suppress
noise. An internal 32-Ω MOSFET connected to the CS input discharges the external current sense filter capacitor
at the conclusion of every cycle. The discharge MOSFET remains on for an additional 50 ns after the HO or LO
driver switches high to blank leading edge transients in the current sensing circuit. Discharging the CS pin filter
each cycle and blanking leading edge spikes reduces the filtering requirements and improves the current sense
response time.
The current sense comparator is very fast and responds to short duration noise pulses. Layout considerations
are critical for the current sense filter and sense resistor. The capacitor associated with the CS filter must be
placed very close to the device and must be connected directly to the CS and AGND pins. If a current sense
transformer is used, both leads of the transformer secondary must be routed to the filter network, which must be
located close to the IC. If a sense resistor located in the source of the main MOSFET switch is used for current
sensing, a low-inductance type of resistor is required. When designing with a current sense resistor, all of the
noise sensitive low-power ground connections must be connected together near the AGND pin, and a single
connection must be made to the power ground (sense resistor ground point).
7.3.6 Overload Protection Timer
The LM5035 provides a current-limit restart timer (see Figure 11) to disable the outputs and force a delayed
restart (hiccup mode) if a current limit condition is repeatedly sensed. The number of cycle-by-cycle current-limit
events required to trigger the restart is programmable by the external capacitor at the RES pin. During each
PWM cycle, the LM5035 either sources or sinks current from the RES pin capacitor. If no current limit is detected
during a cycle, an 12-µA discharge current sink is enabled to pull the RES pin to ground. If a current limit is
detected, the 12-µA sink current is disabled and a 22-µA current source causes the voltage at the RES pin to
gradually increase. The LM5035 protects the converter with cycle-by-cycle current limiting while the voltage at
RES pin increases. If the RES voltage reaches the 2.5-V threshold, the following restart sequence occurs (also
see Figure 11):
1. The RES capacitor and SS capacitors are fully discharged.
2. The soft-start current source is reduced from 55 µA to 1 µA.
3. The SS capacitor voltage slowly increases. When the SS voltage reaches ≊1 V, the PWM comparator will
produce the first narrow output pulse. After the first pulse occurs, the SS source current reverts to the normal
55-µA level. The SS voltage increases at its normal rate, gradually increasing the duty cycle of the output
drivers.
4. If the overload condition persists after restart, cycle-by-cycle current limiting will begin to increase the voltage
on the RES capacitor again, repeating the hiccup mode sequence.
5. If the overload condition no longer exists after restart, the RES pin will be held at ground by the 12-µA
current sink and normal operation resumes.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
13
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
Feature Description (continued)
The overload-timer function is very versatile and can be configured for the following modes of protection:
Cycle-by-cycle only The hiccup mode can be completely disabled by connecting a zero to 50-kΩ resistor from
the RES pin to AGND. In this configuration, the cycle-by-cycle protection will limit the output current
indefinitely and no hiccup sequences will occur.
Hiccup only The timer can be configured for immediate activation of a hiccup sequence upon detection of an
overload by leaving the RES pin open circuit.
Delayed Hiccup Connecting a capacitor to the RES pin provides a programmed interval of cycle-by-cycle
limiting before initiating a hiccup mode restart, as previously described. The dual advantages of this
configuration are that a short term overload will not cause a hiccup mode restart but during
extended overload conditions, the average dissipation of the power converter will be very low.
Externally Controlled Hiccup The RES pin can also be used as an input. By externally driving the pin to a level
greater than the 2.5-V hiccup threshold, the controller will be forced into the delayed restart
sequence. For example, the external trigger for a delayed restart sequence could come from an
overtemperature protection circuit or an output overvoltage sensor.
Current
Sense
Circuit
Current
Limit
CS
5V
Restart
Current
Source
Logic
0.25V
CLK
22 PA
RES
12 PA
CRES
SS
To Output
Drivers
COMP
Voltage
Feedback
PWM
2.5V
S
R Q
Drivers Off
1 PA
CSS
Restart
Comparator
Restart
Latch
55 PA
SS
55 PA
100 mV
SS
Logic
Drivers Off
Soft-start
LM5035
Figure 11. Current-Limit Restart Circuit
2.5V
Current Limit Detected
at CS
RES
0V
5V
+55 PA
#1V
+1 PA
SS
LO
HO
t1
t2
t3
Figure 12. Current-Limit Restart Timing
14
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Feature Description (continued)
REF
5V
FEED-FORWARD RAMP
+
5k
_
1V
COMP
1:1
LM4041
Voltage
feedback
PWM
COMPARATOR
Potential across
Optocoupler detector
is constant (approx. 4.3V)
SOFT-START
LM5035
Figure 13. Optocoupler-to-COMP Interface
7.3.7 Soft-Start
The soft-start circuit allows the regulator to gradually reach a steady state operating point, thereby reducing startup stresses and current surges. When bias is supplied to the LM5035, the SS pin capacitor is discharged by an
internal MOSFET. When the UVLO, VCC, and REF pins reach their operating thresholds, the SS capacitor is
released and charged with a 55-µA current source. The PWM comparator control voltage is clamped to the SS
pin voltage by an internal amplifier. When the PWM comparator input reaches 1 V, output pulses commence with
slowly increasing duty cycle. The voltage at the SS pin eventually increases to 5 V, while the voltage at the PWM
comparator increases to the value required for regulation, as determined by the voltage feedback loop.
One method to shutdown the regulator is to ground the SS pin, which forces the internal PWM control signal to
ground, thus quickly reducing the output duty cycle to zero. Releasing the SS pin begins a soft-start cycle, and
normal operation resumes. A second shutdown method is discussed in the UVLO section.
7.3.8 Soft-Stop
If the UVLO pin voltage falls below the 1.25-V standby threshold but above the 0.4-V shutdown threshold, the
55-µA SS pin source current is disabled and a 55-µA sink current discharges the soft-start capacitor. As SS
voltage falls and clamps the PWM comparator input, the PWM duty cycle will gradually fall to zero. The soft-stop
feature produces a gradual reduction of the power converter output voltage. This soft-stop method of turning off
the converter reduces energy in the output capacitor before control of the main and synchronous rectification
MOSFETs is disabled. The PWM pulses may cease before the SS voltage reduces the duty cycle if the VCC or
REF voltage drops below the respective undervoltage thresholds during the soft-stop process.
7.3.9 PWM Comparator
The pulse width modulation (PWM) comparator compares the voltage ramp signal at the RAMP pin to the looperror signal. This comparator is optimized for speed in order to achieve minimum controllable duty cycles. The
loop-error signal is received from the external feedback, and the isolation circuit is in the form of a control current
into the COMP pin. The COMP pin current is internally mirrored by a matched pair of NPN transistors that sink
current through a 5-kΩ resistor connected to the 5-V reference. The resulting control voltage passes through a
1-V level shift before being applied to the PWM comparator.
An optocoupler detector can be connected between the REF pin and the COMP pin (see Figure 13). Because
the COMP pin is controlled by a current input, the potential difference across the optocoupler detector is nearly
constant. The bandwidth-limiting phase delay, which is normally introduced by the significant capacitance of the
optocoupler, is thereby greatly reduced. Higher loop bandwidths can be realized because the bandwidth-limiting
pole associated with the optocoupler is now at a much higher frequency. The PWM comparator polarity is
configured such that, with no current into the COMP pin, the controller produces the maximum duty cycle at the
main gate driver outputs, HO and LO.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
15
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
Feature Description (continued)
7.3.10 Feedforward Ramp and Volt-Second Clamp
An external resistor (RFF) and capacitor (CFF) connected to VIN, AGND, and the RAMP pin are required to create
the PWM ramp signal. The slope of the signal at RAMP will vary in proportion to the input line voltage. This
varying slope provides line feedforward information necessary to improve line transient response with voltage
mode control. The RAMP signal is compared to the error signal by the pulse width modulator comparator to
control the duty cycle of the HO and LO outputs. With a constant error signal, the on-time (TON) varies inversely
with the input voltage (VIN) to stabilize the volt-second product of the transformer primary signal. The power path
gain of conventional voltage-mode pulse-width modulators (oscillator generated ramp) varies directly with input
voltage. The use of a line generated ramp (input voltage feedforward) nearly eliminates this gain variation. As a
result, the feedback loop is only required to make very small corrections for large changes in input voltage.
In addition to the PWM comparator, a volt-second clamp comparator also monitors the RAMP pin. If the ramp
amplitude exceeds the 2.5-V threshold of the volt-second clamp comparator, the on-time is terminated. The CFF
ramp capacitor is discharged by an internal 32-Ω discharge MOSFET controlled by the volt-second clamp
comparator. If the RAMP signal does not exceed 2.5 V before the end of the clock period, the internal clock will
enable the discharge MOSFET to reset capacitor CFF.
By proper selection of RFF and CFF values, the maximum on-time of HO and LO can be set to the desired
duration. The on-time set by the volt-second clamp varies inversely to the line voltage because the RAMP
capacitor is charged by a resistor (RFF) connected to VIN, while the threshold of the clamp is a fixed voltage
(2.5 V). An example will illustrate the use of the volt-second clamp comparator to achieve a 50% duty cycle limit
at 200 kHz with a 48-V line input. A 50% duty cycle at a 200 kHz requires a 2.5-µs on-time. To achieve this
maximum on-time clamp level, use Equation 1:
§
¨
©
In
§
¨1©
2.5V -1
VIN
=
2.5 Ps + 0.25 Ps
In
§
¨1©
§
¨
©
TON + 10%
RFF x CFF =
2.5V -1
48V
= 51.4 Ps
(1)
The recommended capacitor value range for CFF is 100 pF to 1000 pF. A standard value of 470 pF can be paired
with 110 kΩ to approximate the desired 51.4-µs time constant. If load-transient response is slowed by the 10%
margin, the RFF value can be increased. The system signal-to-noise will be slightly decreased by increasing
RFF × CFF.
7.3.11 Oscillator, Sync Capability
The LM5035 oscillator frequency is set by a single external resistor connected between the RT and AGND pins.
To set a desired oscillator frequency, the necessary RT resistor is calculated from Equation 2:
§ 1
¨
© FOSC
§
¨
©
RT =
- 110 ns x 6.25 x 109
(2)
For example, if the desired oscillator frequency is 400 kHz (HO and LO each switching at 200 kHz) a 15-kΩ
resistor would be the nearest standard one percent value.
Each output (HO, LO, SR1 and SR2) switches at half the oscillator frequency. The voltage at the RT pin is
internally regulated to a nominal 2 V. The RT resistor must be located as close as possible to the IC and
connected directly to the pins (RT and AGND). The tolerance of the external resistor and the frequency tolerance
indicated in the Electrical Characteristics must be taken into account when determining the worst-case frequency
range.
16
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Feature Description (continued)
The LM5035 can be synchronized to an external clock by applying a narrow pulse to the RT pin. The external
clock must be at least 10% higher than the free-running oscillator frequency set by the RT resistor. If the external
clock frequency is less than the RT resistor programmed frequency, the LM5035 will ignore the synchronizing
pulses. The synchronization pulse width at the RT pin must be a minimum of 15-ns wide. The clock signal must
be coupled into the RT pin through a 100-pF capacitor or a value small enough to ensure the pulse width at RT
is less than 60% of the clock period under all conditions. When the synchronizing pulse transitions low-to-high
(rising edge), the voltage at the RT pin must be driven to exceed 3.2 V from its nominal 2-V DC level. During the
low time of the clock signal, the voltage at the RT pin will be clamped at 2-V DC by an internal regulator. The
output impedance of the RT regulator is approximately 100 Ω. The RT resistor is always required, whether the
oscillator is free running or externally synchronized.
7.3.12 Gate-Driver Outputs (HO and LO)
The LM5035 provides two alternating gate-driver outputs, the floating high-side gate driver HO and the ground
referenced low-side driver LO. Each driver can source 1.25 A and sink 2-A peak. The HO and LO outputs
operate in an alternating manner at one-half of the internal oscillator frequency. The LO driver is powered directly
by the VCC regulator. The HO gate driver is powered from a bootstrap capacitor connected between HB and HS.
An external diode connected between VCC (anode pin) and HB (cathode pin) provides the high-side gate driver
power by charging the bootstrap capacitor from VCC when the switch node (HS pin) is low. When the high-side
MOSFET is turned on, HB rises to a peak voltage equal to VVCC + VHS where VHS is the switch-node voltage.
The HB and VCC capacitors must be placed close to the pins of the LM5035 to minimize voltage transients due
to parasitic inductances because the peak current sourced to the MOSFET gates can exceed 1.25 A. The
recommended value of the HB capacitor is 0.01 µF or greater. A low-ESR or low-ESL capacitor, such as a
surface-mount ceramic, must be used to prevent voltage droop during the HO transitions.
The maximum duty cycle for each output is limited to slightly less than 50%, due to the internally fixed dead time
and any programmed sync rectifier delay. The typical dead time in this condition is 70 ns. The programmed sync
rectifier delay is determined by the DLY pin resistor. If the COMP pin is open circuit, the outputs will operate at
maximum duty cycle. The maximum duty cycle for each output can be calculated with Equation 3:
1
T - T - T1
2 S D
Maximum Duty Cycle =
TS
where
•
•
•
TS is the period of one complete cycle for either the HO or LO outputs
TD is the internally fixed dead time
and T1 is the programmed sync rectifier delay
(3)
For example, if the oscillator frequency is 200 kHz, each output will cycle at 100 kHz (TS = 10 µs). Using the
nominal dead time of 70 ns and no programmed delay, the maximum duty cycle at this frequency is calculated to
be 49.3%. Using a programmed sync rectifier delay of 100 ns, the maximum duty cycle is reduced to 48.3%.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
17
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
Feature Description (continued)
7.3.13 Synchronous Rectifier Control Outputs (SR1 and SR2)
Synchronous rectification (SR) of the transformer secondary provides higher efficiency, especially for low-output
voltage converters. The reduction of rectifier forward-voltage drop (0.5 V – 1.5 V) to 10 mV – 200 mV VDS voltage
for a MOSFET, significantly reduces rectification losses. In a typical application, the transformer secondary
winding is center tapped, with the output-power inductor in series with the center tap. The SR MOSFETs provide
the ground path for the energized secondary winding and the inductor current. Figure 14 shows that the SR2
MOSFET is conducting while HO enables power transfer from the primary. The SR1 MOSFET must be disabled
during this period, because the secondary winding connected to the SR1 MOSFET drain is twice the voltage of
the center tap. At the conclusion of the HO pulse, the inductor current continues to flow through the SR1
MOSFET body diode. Because the body diode causes more loss than the SR MOSFET, efficiency can be
improved by minimizing the T2 period, while maintaining sufficient timing margin over all conditions (component
tolerances, and so on) to prevent shoot-through current. When LO enables power transfer from the primary, the
SR1 MOSFET is enabled, and the SR2 MOSFET is off.
HO
SR1
T1
T2
LO
SR2
T1
T2
Figure 14. HO, LO, SR1 and SR2 Timing Diagram
During the time that neither HO nor LO is active, the inductor current is shared between both the SR1 and SR2
MOSFETs, which effectively shorts the transformer secondary and cancels the inductance in the windings. The
SR2 MOSFET is disabled before LO delivers power to the secondary to prevent power being shunted to ground.
The SR2 MOSFET body diode continues to carry about half the inductor current until the primary power raises
the SR2 MOSFET drain voltage and reverse biases the body diode. Ideally, dead-time T1 would be set to the
minimum time that allows the SR MOSFET to turn off before the SR MOSFET body diode starts conducting.
The SR1 and SR2 outputs are powered directly by the VCC regulator. Each output is capable of sourcing and
sinking 0.5-A peak. Typically, the SR1 and SR2 signals control SR MOSFET gate drivers through a pulse
transformer. The actual gate sourcing and sinking currents are provided by the secondary-side bias supply and
gate drivers.
The timing of SR1 and SR2 with respect to HO and LO is shown in Figure 14. SR1 is configured out-of-phase
with HO, and SR2 is configured out-of-phase with LO. The dead time between transitions is programmable by a
resistor connected from the DLY pin to the AGND pin. Typically, RDLY is set in the range of 10 kΩ to 100 kΩ. The
dead-time periods can be calculated using Equation 4 and Equation 5:
T1 = [RDLY × 2.8 ps] + 20 ns
T2 = [RDLY × 1.35 ps] + 6 ns
(4)
(5)
To set the minimum dead time (propagation delays only), the DLY pin must be left open or connected to the REF
pin. Any resistor value above 300 kΩ connected between the DLY pin and AGND will also provide the minimum
period (approximately 5 ns).
18
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Feature Description (continued)
7.3.14 Thermal Protection
Internal thermal-shutdown circuitry is provided to protect the integrated circuit in the event that the maximumrated junction temperature is exceeded. When activated, typically at 165°C, the controller is forced into a lowpower standby state with the output drivers (HO, LO, SR1, and SR2) and the bias regulators (VCC and REF)
disabled. This helps prevent catastrophic failures from accidental device overheating. During thermal shutdown,
the soft-start capacitor is fully discharged, and the controller follows a normal start-up sequence after the junction
temperature falls to the operating level (145°C).
7.4 Device Functional Modes
The LM5035 can be used as a half-bridge PWM controller or as a push-pull PWM controller.
To implement the LM5035 in a push-pull application, the HB pin is connected to VCC and the HS pin is
connected to PGND. The LM5035 will deliver 180º out-of-phase ground-referenced PWM signals to the gates of
the power MOSFETS.
The high-side driver has an HS-to-GND maximum voltage rating of 105 V, but in higher-voltage applications the
high-side MOSFET can be driven with a gate-drive transformer.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
19
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers must
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The following information is intended to provide guidelines for the power-supply designer using the LM5035.
8.2 Typical Application
Figure 15 shows an example of a 100-W half-bridge power converter controlled by the LM5035. The operating
input-voltage range (VPWR) is 36 V to 75 V, and the output voltage is 3.3 V. The output-current capability is 30 A.
Current sense transformer T2 provides information to the CS pin for current-limit protection. The error amplifier
and reference, U3 and U5 respectively, provide voltage feedback through optocoupler U4. Synchronous rectifiers
(Q4, Q5, Q6, and Q7) minimize rectification losses in the secondary. An auxiliary winding on transformer T1
provides power to the LM5035 VCC pin when the output is in regulation. The input voltage UVLO thresholds are
≊ 34 V for increasing VPWR, and ≊ 32 V for decreasing VPWR. The circuit can be shut down by driving the
ON/OFF input (J2) below 1.25 V with an open-collector or open-drain circuit. An external synchronizing
frequency can be applied through a 100-pF capacitor to the RT input (U1 pin 5). The regulator output is current
limited at ≊ 34 A.
20
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Figure 15. Application Circuit
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
21
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
8.2.1 Design Requirements
Table 1 lists example design parameters for the application circuit layout in Figure 15.
Table 1. Design Parameters
PARAMETER
MIN
Input voltage (VIN)
NOM
36
MAX
72
Output voltage (VOUT)
3.3
Output current (IOUT)
0
400
Efficiency (full load)
89%
Efficiency (half load)
92%
Load regulation
0.2%
Line regulation
0.1%
V
V
30
Switching frequency
UNIT
A
kHz
undervoltage lock-out (ON)
33.9
V
undervoltage lock-out (OFF)
31.9
V
Line overvoltage protection (ON)
79.4
V
Line overvoltage protection (OFF)
78.3
V
8.2.2 Detailed Design Procedure
8.2.2.1 VIN
The voltage applied to the VIN pin, which may be the same as the system voltage applied to the power
transformer primary (VPWR), can vary in the range from 13 V to 105 V. The current into VIN depends primarily on
the gate charge provided to the output drivers, the switching frequency, and any external loads on the VCC and
REF pins. It is recommended the filter shown in Figure 16 be used to suppress transients which may occur at the
input supply. This is particularly important when VIN is operated close to the maximum operating rating of the
LM5035.
When power is applied to VIN and the UVLO pin voltage is greater than 0.4 V, the VCC regulator is enabled and
supplies current into an external capacitor connected to the VCC pin. When the voltage on the VCC pin reaches
the regulation point of 7.6 V, the voltage reference (REF) is enabled. The reference regulation set point is 5 V.
The HO, LO, SR1, and SR2 outputs are enabled when the two bias regulators reach their set point and the
UVLO pin potential is greater than 1.25 V. In typical applications, an auxiliary transformer winding is connected
through a diode to the VCC pin. This winding must raise the VCC voltage above 8.3 V to shut off the internal
start-up regulator.
After the outputs are enabled and the external VCC supply voltage has begun supplying power to the IC, the
current into VIN drops below 1 mA. VIN must remain at a voltage equal to or above the VCC voltage to avoid
reverse current through protection diodes.
VPWR
50
VIN
LM5035
0.1 PF
Figure 16. Input-Transient Protection
22
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
8.2.2.2 For Applications >100 V
For applications where the system input voltage exceeds 100 V or the IC power dissipation is of concern, the
LM5035 can be powered from an external start-up regulator as shown in Figure 17. In this configuration, the VIN
and the VCC pins must be connected together, which allows the LM5035 to be operated below 13 V. The voltage
at the VCC pin must be greater than 8.3 V, yet not exceed 15 V. An auxiliary winding can be used to reduce the
power dissipation in the external regulator once the power converter is active. The NPN base-emitter reverse
breakdown voltage, which can be as low as 5 V for some transistors, must be considered when selecting the
transistor.
8.2.2.3 Current Sense
The CS pin needs to receive an input signal representative of the primary current of the transformer, either from
a current sense transformer or from a resistor in series with the source of the LO switch, as shown in Figure 18
and Figure 19. In both cases, the sensed current creates a ramping voltage across R1, and the RF / CF filter
suppresses noise and transients. R1, RF and CF must be located as close to the LM5035 as possible, and the
ground connection from the current sense transformer, or R1, must be a dedicated track to the AGND pin. The
current sense components must provide greater than 0.25 V at the CS pin when an overcurrent condition exists.
VPWR
VIN
8.3V - 15V
(from aux winding)
VCC
LM5035
9V
Figure 17. Start-Up Regulator for VPWR >100 V
VPWR
Power
Transformer
Current
Sense
Q1
VIN
RF
CS
CF
R1
AGND
HO
Q2
LO
LM5035
Figure 18. Current Sense Using Current Sense Transformer
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
23
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
VPWR
Power
Transformer
Q1
VIN
HO
Q2
LO
RF
CS
CF
R1
Current
Sense
AGND
LM5035
Figure 19. Current Sense Using Current Sense Resistor (R1)
If the current sense resistor method is used, the overcurrent condition will only be sensed while LO is driving the
low-side MOSFET. Overcurrent while HO is driving the high-side MOSFET will not be detected. In this
configuration, it will take 4 times as long for continuous cycle-by-cycle current limiting to initiate a restart event
since each overcurrent event during LO enables the 22-µA RES pin current source for one oscillator period, and
then the lack of an overcurrent event during HO enables the 12-µA RES pin current sink for one oscillator period.
The time average of this toggling is equivalent to a continuous 5-µA current source into the RES capacitor,
increasing the delay by a factor of four. The value of the RES capacitor can be reduced to decrease the time
before restart cycle is initiated.
When using the resistor current sense method, an imbalance in the input capacitor voltages may develop when
operating in cycle-by-cycle current limiting mode. If the imbalance persists for an extended period, excessive
currents in the non-sensed MOSFET, and possible transformer saturation may result. This condition is inherent
to the half-bridge topology operated with cycle-by-cycle current limiting and is compounded by only sensing in
one leg of the half-bridge circuit. The imbalance is greatest at large duty cycles (low input voltages). If using this
method, it is recommended that the capacitor on the RES pin be no larger than 220 pF. Check the final circuit
and reduce the RES capacitor further, or omit the capacitor completely to ensure the voltages across the bridge
capacitors remain balanced. The current limit value may decrease slightly as the RES capacitor is reduced.
8.2.2.4 HO, HB, HS, and LO
Attention must be given to the PC board layout for the low-side driver and the floating high-side driver pins HO,
HB and HS. A low ESR or ESL capacitor (such as a ceramic surface mount capacitor) must be connected close
to the LM5035, between HB and HS to provide high peak currents during turnon of the high-side MOSFET. The
capacitor must be large enough to supply the MOSFET gate charge (Qg) without discharging to the point where
the drop in gate voltage affects the MOSFET RDS(ON). Use Equation 6 to calculate the value for CBOOST. A value
that is ten to 20 times Qg is recommended.
CBOOST = 20 x
Qg
VCC
(6)
The diode (DBOOST) that charges CBOOST from VCC when the low-side MOSFET is conducting must be capable
of withstanding the full converter input voltage range. When the high-side MOSFET is conducting, the reverse
voltage at the diode is approximately the same as the MOSFET drain voltage because the high-side driver is
boosted up to the converter input voltage by the HS pin, and the high side MOSFET gate is driven to the HS
voltage plus VCC. Since the anode of DBOOST is connected to VCC, the reverse potential across the diode is
equal to the input voltage minus the VCC voltage. DBOOST average current is less than 20 mA in most
applications, so a low current ultra-fast recovery diode is recommended to limit the loss due to diode junction
capacitance. Schottky diodes are also a viable option, particularly for lower input voltage applications, but
attention must be paid to leakage currents at high temperatures.
24
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
The internal gate drivers need a very low impedance path to the respective decoupling capacitors; the VCC cap
for the LO driver and CBOOST for the HO driver. These connections must be as short as possible to reduce
inductance and as wide as possible to reduce resistance. The loop area, defined by the gate connection and its
respective return path, must be minimized.
The high-side gate driver can also be used with HS connected to PGND for applications other than a half bridge
converter (for example, push-pull). The HB pin is then connected to VCC, or any supply greater than the highside driver undervoltage lockout (approximately 6.5 V). In addition, the high-side driver can be configured for high
voltage offline applications where the high-side MOSFET gate is driven via a gate drive transformer.
8.2.2.5 Programmable Delay (DLY)
The RDLY resistor programs the delays between the SR1 and SR2 signals and the HO and LO driver outputs.
Figure 14 shows the relationship between these outputs. The DLY pin is nominally set at 2.5 V and the current is
sensed through RDLY to ground. This current is used to adjust the amount of dead time before the HO and LO
pulse (T1) and after the HO and LO pulse (T2). Typically RDLY is in the range of 10 kΩ to 100 kΩ. The dead-time
periods can be calculated using Equation 7 and Equation 8:
T1 = [RDLY × 2.8 ps] + 20 ns
T2 = [RDLY × 1.35 ps] + 6 ns
(7)
(8)
T1 and T2 can be set to minimum by not connecting a resistor to DLY, connecting a resistor greater than 300 kΩ
from DLY to ground, or connecting DLY to the REF pin. This may cause lower than optimal system efficiency if
the delays through the SR signal transformer network, the secondary gate drivers and the SR MOSFETs are
greater than the delay to turn on the HO or LO MOSFETs. must an SR MOSFET remain on while the opposing
primary MOSFET is supplying power through the power transformer, the secondary winding will experience a
momentary short circuit, causing a significant power loss to occur.
When choosing the RDLY value, worst case propagation delays and component tolerances must be considered to
assure that there is never a time where both SR MOSFETs are enabled AND one of the primary side MOSFETs
is enabled. The time period T1 must be set so that the SR MOSFET has turned off before the primary MOSFET
is enabled. Conversely, T1 and T2 must be kept as low as tolerances allow to optimize efficiency. The SR body
diode conducts during the time between the SR MOSFET turns off and the power transformer begins supplying
energy. Power losses increase when this happens since the body diode voltage drop is many times higher than
the MOSFET channel voltage drop. The interval of body diode conduction can be observed with an oscilloscope
as a negative 0.7 V to 1.5 V pulse at the SR MOSFET drain.
8.2.2.6 UVLO and OVP Voltage Divider Selection for R1, R2, and R3
Two dedicated comparators connected to the UVLO and OVP pins are used to detect undervoltage and
overvoltage conditions. The threshold value of these comparators, VUVLO and VOVP, is 1.25 V (typical). The two
functions can be programmed independently with two voltage dividers from VIN to AGND as shown in Figure 20
and Figure 21, or with a three-resistor divider as shown in Figure 22. Independent UVLO and OVP pins provide
greater flexibility for the user to select the operational voltage range of the system. Hysteresis is accomplished by
23-µA current sources (IUVLO and IOVP), which are switched on or off into the sense pin resistor dividers as the
comparators change state.
When the UVLO pin voltage is below 0.4 V, the controller is in a low current shutdown mode. For a UVLO pin
voltage greater than 0.4 V but less than 1.25 V the controller is in standby mode. Once the UVLO pin voltage is
greater than 1.25 V, the controller is fully enabled. Two external resistors can be used to program the minimum
operational voltage for the power converter as shown in Figure 20. When the UVLO pin voltage falls below the
1.25-V threshold, an internal 23-µA current sink is enabled to lower the voltage at the UVLO pin, thus providing
threshold hysteresis. Resistance values for R1 and R2 can be determined from Equation 9 and Equation 10.
VHYS
R1 =
23 PA
(9)
1.25V x R1
R2 =
VPWR ± 1.25V ± (23 PA x R1)
where
•
•
VPWR is the desired turnon voltage
VHYS is the desired UVLO hysteresis at VPWR
(10)
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
25
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
For example, if the LM5035 is to be enabled when VPWR reaches 34 V, and disabled when VPWR is decreased
to 32 V, R1 must be 87 kΩ, and R2 must be 3.54 kΩ. The voltage at the UVLO pin must not exceed 7 V at any
time. Be sure to check both the power and voltage rating (0603 resistors can be rated as low as 50 V) for the
selected R1 resistor.
VPWR
LM5035
R1
1.25V
UVLO
Disable Output Drivers
23 PA
0.4V
R2
Disable VCC and REF Regulators
Figure 20. Basic UVLO Configuration
VPWR
LM5035
5V
23 PA
R1
OVP
STANDBY
1.25V
R2
Figure 21. Basic Overvoltage Protection
VPWR
LM5035
R1
UVLO
1.25V
Disable Output Drivers
23 PA
0.4V
R2
Disable VCC and REF Regulators
5V
23 PA
OVP
1.25V
STANDBY
R3
Figure 22. UVLO and OVP Divider
The impedance seen looking into the resistor divider from the UVLO and OVP pins determines the hysteresis
level. UVLO and OVP enable and disable thresholds are calculated using the equations in Table 2 for the threeresistor divider listed in Figure 22.
26
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
Table 2. UVO and OVP Divider Formulas
EQUATION
§ R1
©
+ R2 + R 3
R2 + R3
Outputs enabled due to VIN rising above UVLO threshold
UVLOon = UVLOoff + (23 µA × R1)
Outputs disabled due to VIN rising above OVP threshold
OVPoff = 1.25V x ¨¨
§ R1
©
Outputs enabled due to VIN falling below OVP threshold
+ R2 + R 3
R3
§
¨
¨
©
UVLOoff = 1.25V x ¨¨
Outputs disabled due to VIN falling below UVLO threshold
§
¨
¨
©
THRESHOLD
(11)
(12)
OVPon = OVPoff – [23 µA × (R1 + R2)]
The equations listed in Table 2 calculate the typical operating ranges of undervoltage and overvoltage
thresholds. For example, for resistor values R1 = 86.6 kΩ, R2 = 2.1 kΩ and R3 = 1.4 kΩ the calculated thresholds
are as follows:
• UVLO turnoff = 32.2 V
• UVLO turnon = 34.2 V
• OVP turnon = 78.4 V
• OVP turnoff = 80.5 V
VPWR
LM5035
R1
UVLO
1.25V
STANDBY
23 PA
STANDBY
OFF
0.4V
R2
OFF
Figure 23. Remote Standby and Disable Control
To maintain the accuracy of the threshold, a resistor tolerance of 1% or better is recommended.
The design process begins with the selection of the voltage difference between the UVLO enabling and disabling
thresholds. This selection also sets the approximate difference between OVP enabling and disabling regulation.
Use Equation 13 to calculate the value of R1.
UVLOon - UVLOoff
R1 =
23 PA
(13)
Next, the combined resistance of R2 and R3 is calculated by selecting the threshold for the UVLO disabling
threshold. Use Equation 14 to calculate the value of RCOMBINED.
1.25V x R1
RCOMBINED =
UVLOoff ± 1.25V
(14)
The value of R3 is then determined by selecting the OVP disabling threshold. Use Equation 15 to calculate the
value of R3.
1.25V x (R1 + RCOMBINED)
R3 =
OVPoff
(15)
Finally, subtract the value of R3 from the value of RCOMBINED calculate the value of R2 as shown in Equation 16.
R2 = RCOMBINED — R3
(16)
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
27
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
Remote configuration of the operational modes of the controller can be accomplished with open drain devices
connected to the UVLO pin as shown in Figure 23.
8.2.2.7 Fault Protection
The overvoltage protection (OVP) comparator of the LM5035 can be configured for line or load fault protection or
thermal protection using an external temperature sensor or thermistor. Figure 21 shows a line over voltage
shutdown application using a voltage divider between the input power supply, VPWR, and AGND to monitor the
line voltage.
Figure 24 demonstrates the use of the OVP pin for latched output overvoltage fault protection, using a zener and
optocoupler. When VOUT exceeds the conduction threshold of the optocoupler diode and zener, the optocoupler
momentarily turns on Q1 and the LM5035 enters standby mode, disabling the drivers and enabling the hysteresis
current source on the OVP pin. When the current source is enabled, the OVP voltage will remain at 2.3 V (23 µA
× 100 kΩ) without additional drive from the external circuit. If the optocoupler transistor emitter were directly
connected to the OVP pin, then leakage current in the zener diode amplified by the gain of the optocoupler could
falsely trip the protection latch. R1 and Q1 are added reduce the sensitivity to low level currents in the
optocoupler. Using the values of Figure 24, the optocoupler collector current must equal VBE(Q1) / R1 = 350 µA
before OVP latches. Once the controller has switched to standby mode, the outputs no longer switch but the
VCC and REF regulators continue functioning and supply bias to the external circuitry. VCC must fall below 6.2 V
or the UVLO pin must fall below 0.4 V to clear the OVP latch.
VREF
R1
2k
VOUT
LM5035
5V
23 PA
Q1
OVP
STANDBY
1.25V
R2
100k
Figure 24. Latched Load Overvoltage Protection
Figure 25 shows an application of the OVP comparator for Remote Thermal Protection using a thermistor (or
multiple thermistors) which may be located near the main heat sources of the power supply. The negative
temperature coefficient (NTC) thermistor is nearly logarithmic, and in this example a 100kΩ thermistor with the β
material constant of 4500 kelvins changes to approximately 2 kΩ at 130°C. Setting R1 to one-third of this
resistance (665 Ω) establishes 130°C as the desired trip point (for VREF = 5 V). In a temperature band from 20°C
below to 20°C above the OVP threshold, the voltage divider is nearly linear with 25 mV per°C sensitivity.
R2 provides temperature hysteresis by raising the OVP comparator input by R2 × 23 µA. For example, if a 22-kΩ
resistor is selected for R2, then the OVP pin voltage will increase by 22 kΩ × 23 µA = 506 mV. The NTC
temperature must therefore fall by 506 mV / 25 mV per°C = 20°C before the LM5035 switches from the standby
mode to the normal mode.
VREF
LM5035
5V
23 PA
NTC
THERMISTOR
T
R2
R1
OVP
1.25V
STANDBY
Figure 25. Remote Thermal Protection
28
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
8.2.2.8 HICCUP Mode Current-Limit Restart (RES)
The basic operation of the hiccup mode current limit restart is described in the functional description. The delay
time to restart is programmed with the selection of the RES pin capacitor CRES as shown in Figure 25.
2.5V
Current Limit Detected
at CS
RES
0V
5V
+55 PA
#1V
+1 PA
SS
LO
HO
t1
t2
t3
Figure 26. Hiccup Overload Restart Timing
In the case of continuous cycle-by-cycle current-limit detection at the CS pin, refer to Figure 26 and use
Equation 17 to calculate the time required for CRES to reach the 2.5-V hiccup mode threshold.
t1 =
CRES x 2.5V
22 PA
= 114 k: x CRES
(17)
For example, if CRES = 0.01 µF the time, t1, is approximately 1.14 ms.
The cool down time, t2 is set by the soft-start capacitor (CSS) and the internal 1-µA SS current source. Use
Equation 18 to calculate the value of t2.
t2 =
CSS x 1V
1 PA
= 1 M: x CSS
(18)
If CSS = 0.01 µF, the value of t2 is ≊ 10 ms.
The soft-start time t3 is set by the internal 55-µA current source. Use Equation 19 to calculate the value of t3.
t3 =
CSS x 4V
= 73 k: x CSS
55 PA
(19)
If CSS = 0.01 µF, the value of t3 is ≊ 730 µs.
The time t2 provides a periodic cool-down time for the power converter in the event of a sustained overload or
short circuit. This off time results in lower average input current and lower power dissipation within the power
components. It is recommended that the ratio of t2 / (t1 + t3) be in the range of 5 to 10 to take advantage of this
feature.
If the application requires no delay from the first detection of a current limit condition to the onset of the hiccup
mode (t1 = 0), the RES pin can be left open (no external capacitor). If it is desired to disable the hiccup mode
entirely, the RES pin must be connected to ground (AGND).
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
29
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
8.2.3 Application Curves
Figure 29 shows typical output ripple seen across the output terminals (with standard 10-µF and 1-µF ceramic
capacitors) for an input voltage of 48 V and a load of 30 A. This waveform is typical of most loads and input
voltages.
Figure 30 and Figure 31 show the drain voltage of Q1 with a 5-A load. Figure 30 represents an input voltage of
36 V and Figure 29 represents an input voltage of 72 V.
Figure 32 shows the gate voltages of the synchronous rectifiers. The dead time provided by the 20-kΩ DLY
resistor is difficult to see at this timescale.
VIN = 48 VDC
IOUT = 5 A
Horizontal resolution = 0.5 ms/div
Trace 1: output voltage V/div = 500 mV
Figure 27. Output Voltage During a Typical Start-Up
VIN = 48 VDC
IOUT = 30 A
Trace 1: output ripple voltage V/div = 20 mV
Horizontal resolution = 1 µs/div
Bandwidth limit = 20 MHz
Figure 29. Typical Output Ripple Across the Output
Terminals
30
VIN = 48 VDC
Horizontal resolution = 0.5 ms/div
IOUT = 15 A to 22.5 A
Upper trace: VOUT V/div = 50 mV
Lower trace: IOUT = 15 A to 22.5 A to 15 A
Figure 28. Transient Response for a Load Change
From 15 A to 22.5 A
VIN = 36 VDC
IOUT = 5 A
Trace 1: Q1 drain voltage V/div = 10 V
Horizontal resolution = 1 µs/div
Figure 30. Drain Voltage of Q1 With a 5-A Load
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
LM5035
www.ti.com
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
VIN = 72 VDC
IOUT = 5 A
Trace 1: Q2 drain voltage V/div = 10 V
Horizontal resolution = 1 µs/div
Figure 31. Drain Voltage of Q1 With a 5-A Load
VIN = 48 VDC
IOUT = 5 A
Upper trace: SR1, Q4 gate V/div = 5 V
Middle trace: HS, Q2 drain V/div = 20 V
Lower trace: SR2, Q6 gate V/div = 5 V
Horizontal resolution = 1 µs/div
Figure 32. Gate Voltages of the Synchronous Rectifiers
9 Power Supply Recommendations
The LM5035 can be used to control power levels up to 500 W; therefore, the current levels can be considerable.
Care must be taken in choosing components with the correct current rating which includes: magnetic
components, power MOSFETS and diodes, connectors, and wire sizes. Input and output capacitors must have
the correct ripple current rating. The use of a multilayer PCB is recommended with a copper area chosen to
ensure the LM5035 operates below the maximum junction temperature.
Full power loading must never be attempted without providing for adequate cooling.
10 Layout
10.1 Layout Guidelines
The LM5035 current sense and PWM comparators are very fast, and they respond to short duration noise
pulses. The components at the CS, COMP, SS, OVP, UVLO, DLY, and the RT pins must be as physically close
to the device as possible, thereby minimizing noise pickup on the PC board tracks.
Layout considerations are critical for the current sense filter. If a current sense transformer is used, both leads of
the transformer secondary must be routed to the sense filter components and to the IC pins. The ground side of
the transformer must be connected through a dedicated PC board track to the AGND pin rather than through the
ground plane.
If the current sense circuit employs a sense resistor in the drive transistor source, low inductance resistors must
be used. In this case, all the noise sensitive, low-current ground tracks must be connected in common near the
device, and then a single connection made to the power ground (sense resistor ground point).
The gate drive outputs of the LM5035 must have short, direct paths to the power MOSFETs to minimize
inductance in the PC board traces. The SR control outputs must also have minimum routing distance through the
pulse transformers and through the secondary gate drivers to the sync FETs.
The two ground pins (AGND, PGND) must be connected together with a short, direct connection, to avoid jitter
due to relative ground bounce.
If the internal dissipation of the LM5035 produces high junction temperatures during normal operation, the use of
multiple vias under the IC to a ground plane can help conduct heat away from the IC. Judicious positioning of the
PC board within the end product, along with use of any available air flow (forced or natural convection) will help
reduce the junction temperatures. If using forced air cooling, avoid placing the LM5035 in the airflow shadow of
tall components, such as input capacitors.
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
31
LM5035
SNVS428H – JANUARY 2006 – REVISED OCTOBER 2015
www.ti.com
10.2 Layout Example
VIN
RAMP
VIN
UVLO
REF
OVP
SR1
COMP
SR2
RT
VCC
AGND
To Sense Resistor Positive
To Sense Resistor Return
PGND
CS
LO
To Low Side MOSFET Gate
SS
HO
To High Side MOSFET Gate
DLY
HS
RES
HB
Figure 33. LM5035 Board Layout
11 Device and Documentation Support
11.1 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.2 Trademarks
PowerPAD, E2E are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
11.3 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
32
Submit Documentation Feedback
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: LM5035
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM5035MH/NOPB
ACTIVE
HTSSOP
PWP
20
73
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LM5035
MH
LM5035MHX/NOPB
ACTIVE
HTSSOP
PWP
20
2500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LM5035
MH
LM5035SQ/NOPB
ACTIVE
WQFN
NHZ
24
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
L5035SQ
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
工商网监
湘ICP备2023018690号
