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TPS40170-Q1
SLVSB90B – JANUARY 2012 – REVISED DECEMBER 2014
TPS40170-Q1 4.5-V to 60-V, Wide-Input, Synchronous PWM Buck Controller
1 Features
3 Description
•
•
The TPS40170-Q1 device is a full-featured,
synchronous PWM buck controller that operates at an
input voltage between 4.5 V and 60 V and is
optimized for high-power-density, high-reliability dc-dc
converter applications. The controller implements
voltage-mode control with input-voltage feed-forward
compensation that enables instant response to an
input voltage change. The switching frequency is
programmable from 100 kHz to 600 kHz.
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Qualified for Automotive Applications
AEC-Q100 Qualified With the Following Results
– Device Temperature Grade 1: –40°C to 125°C
Ambient Operating Temperature Range
– Device HBM ESD Classification Level 1C
– Device CDM ESD Classification Level C4B
Wide-Input Voltage Range from 4.5 V to 60 V
600-mV Reference Voltage With 1% Accuracy
Programmable UVLO and Hysteresis
Voltage-Mode Control With Voltage Feed-Forward
Programmable Frequency Between 100 kHz and
600 kHz
Bidirectional Frequency Synchronization With
Master and Slave Option
Low-Side FET Sensing Overcurrent Protection
and High-Side FET Sensing Short-Circuit
Protection With Integrated Thermal Compensation
Programmable Closed-Loop Soft-Start
Supports Pre-Biased Outputs
Thermal Shutdown at 165°C With Hysteresis
Voltage Tracking
Power Good
ENABLE With 1-µA Low-Current Shutdown
8-V and 3.3-V LDO Output
Integrated Bootstrap Diode
20-Pin 4.5-mm × 3.5-mm VQFN (RGY) Package
The TPS40170-Q1 device has a complete set of
system protection and monitoring features such as
programmable UVLO, programmable overcurrent
protection (OCP) by sensing the low-side FET,
selectable short-circuit protection (SCP) by sensing
the high-side FET, and thermal shutdown. The
ENABLE pin allows for system shutdown in a lowcurrent (1-µA typical) mode. The controller supports
pre-biased output, provides an open-drain PGOOD
signal, and has closed-loop soft-start, output-voltage
tracking, and adaptive dead-time control.
The TPS40170-Q1 device provides accurate outputvoltage regulation within 1% accuracy. Additionally,
the controller implements a novel scheme of
bidirectional synchronization with one controller
acting as the master and other downstream
controllers acting as slaves, synchronized to the
master in-phase or 180° out-of-phase. Slave
controllers can be synchronized to an external clock
within ±30% of the free-running switching frequency.
Device Information(1)
PART NUMBER
PACKAGE
2 Applications
•
•
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Advanced Driver Assistance System (ADAS)
Automotive Infotainment and Cluster
VQFN (20)
BODY SIZE (NOM)
TPS40170-Q1
4.50 mm × 3.50 mm
Simplified Schematic
VIN
1
20
ENABLE
UVLO
2
SYNC
3
M/S
4
RT
5
SS
VIN 19
BOOT 18
HDRV 17
VOUT
SW 16
TPS40170
6
TRK
7
FB
8
COMP
9
AGND
VBP 15
LDRV 14
PGND 13
ILIM 12
VDD
PGOOD
10
11
UDG-09219
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.
TPS40170-Q1
SLVSB90B – JANUARY 2012 – REVISED DECEMBER 2014
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
4
5
5
8
Detailed Description ............................................ 11
7.1
7.2
7.3
7.4
8
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
11
12
12
28
Application and Implementation ........................ 31
8.1 Application Information............................................ 31
8.2 Typical Application .................................................. 31
9
Power Supply Recommendations...................... 38
9.1
9.2
9.3
9.4
Bootstrap Resistor...................................................
SW-Node Snubber Capacitor .................................
Input Resistor ..........................................................
LDRV Gate Capacitor .............................................
38
38
38
38
10 Layout................................................................... 39
10.1 Layout Guidelines ................................................. 39
10.2 Layout Example .................................................... 39
11 Device and Documentation Support ................. 43
11.1
11.2
11.3
11.4
11.5
Device Support......................................................
Documentation Support .......................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
43
43
43
43
43
12 Mechanical, Packaging, and Orderable
Information ........................................................... 43
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision A (March 2012) to Revision B
•
Page
Added Handling 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 ............................................................... 4
Changes from Original (January 2012) to Revision A
Page
•
Changed RHDHI, RHDLO and RLDLO MAX values.................................................................................................................... 7
•
Changed IILIM and IILIM(ss) values ............................................................................................................................................. 7
2
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Product Folder Links: TPS40170-Q1
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SLVSB90B – JANUARY 2012 – REVISED DECEMBER 2014
5 Pin Configuration and Functions
RGY PACKAGE
QFN-20
(Top View)
ENABLE
UVLO
1
20 19
SYNC
2
M/S
3
18
BOOT
RT
4
17
HDRV
SS
5
16
SW
VIN
TPS40170
TRK
6
15
VBP
FB
7
14
LDRV
COMP
8
13
PGND
AGND
9
10
VDD
11 12
ILIM
PGOOD
Pin Functions
PIN
I/O
DESCRIPTION
NAME
NO.
AGND
9
—
Analog signal ground. This pin must be electrically connected to power ground PGND externally.
BOOT
18
O
Boot-capacitor node for high-side FET gate driver. The boot capacitor is connected from this pin to SW.
COMP
8
O
Output of the internal error amplifier. The feedback loop compensation network is connected from this pin
to the FB pin.
ENABLE
1
I
This pin must be high for the device to be enabled. If this pin is pulled low, the device is put in a low-powerconsumption shutdown mode.
FB
7
I
Negative input to the error amplifier. The output voltage is fed back to this pin through a resistor-divider
network.
HDRV
17
O
Gate-driver output for the high-side FET.
ILIM
12
I
A resistor from this pin to PGND sets the overcurrent limit. This pin provides source current used for the
overcurrent-protection threshold setting.
LDRV
14
O
Gate driver output for the low-side FET. Also, a resistor from this pin to PGND sets the multiplier factor to
determine the short-circuit current limit. If no resistor is present, the multiplier defaults to 7 times the ILIM
pin voltage.
M/S
3
I
Master- or slave-mode selector pin for frequency synchronization. This pin must be tied to VIN for master
mode. In the slave mode, this pin must be tied to AGND or left floating. If the pin is tied to AGND, the
device synchronizes with a 180° phase shift. If the pin is left floating, the device synchronizes with a 0°
phase shift.
PGND
13
—
Power ground. This pin must externally connect to the AGND at a single point.
PGOOD
11
O
Power-good indicator. This pin is an open-drain output pin, and a 10-kΩ pullup resistor is recommended to
be connected between this pin and VDD.
RT
4
I
A resistor from this pin to AGND sets the oscillator frequency. Even if operating in slave mode, it is required
to have a resistor at this pin to set the free-running switching frequency.
SS
5
I
Soft-start. A capacitor must be connected from this pin to AGND. The capacitor value sets the soft-start
time.
SW
16
I
This pin must connect to the switching node of the synchronous buck converter. The high-side and low-side
FET current sensing are also done from this node.
SYNC
2
I/O
Synchronization. This is a bidirectional pin used for frequency synchronization. In the master mode, it is the
SYNC output pin. In the slave mode, it is a SYNC input pin. If unused, this pin can be left open.
TRK
6
I
Tracking. External signal at this pin is used for output voltage tracking. This pin goes directly to the internal
error amplifier as a positive reference. The lesser of the voltages between VTRK and the internal 600-mV
reference sets the output voltage. If not used, this pin should be pulled up to VDD.
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SLVSB90B – JANUARY 2012 – REVISED DECEMBER 2014
www.ti.com
Pin Functions (continued)
PIN
I/O
DESCRIPTION
NAME
NO.
UVLO
20
I
Undervoltage lockout. A resistor divider on this pin from VIN to AGND can be used to set the UVLO
threshold.
VBP
15
O
8-V regulated output for gate driver. A ceramic capacitor with a value between 1 µF and 10 µF must be
connected from this pin to PGND
VDD
10
O
3.3-V regulated output. A ceramic bypass capacitor with a value between 0.1 µF and 1 µF must be
connected between this pin and the AGND pin and placed closely to this pin.
VIN
19
I
Input voltage for the controller, which is also the input voltage for the dc-dc converter. A 1-µF bypass
capacitor from this pin to AGND must be added and placed closed to VIN.
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1)
MIN
Input voltage
VIN
–0.3
62
M/S
–0.3
VIN
UVLO
–0.3
16
–5
VIN
SW
BOOT
Output voltage
UNIT
V
VSW + 8.8
HDRV
VSW
BOOT
BOOT-SW, HDRV-SW (differential from BOOT or
HDRV to SW)
–0.3
8.8
VBP, LDRV, COMP, RT, ENABLE, PGOOD, SYNC
–0.3
8.8
VDD, FB, TRK, SS, ILIM
–0.3
3.6
AGND-PGND, PGND-AGND
200
200
Grounding
PowerPAD to AGND (must be electrically connected
external to device)
Ambient temperature
TA
Storage temperature
Tstg
(1)
MAX
V
0
mV
–40
125
°C
–55
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.
6.2 ESD Ratings
VALUE
Human body model (HBM), per AEC Q100-002
V(ESD)
(1)
Electrostatic discharge
Charged device model (CDM), per
AEC Q100-011
(1)
UNIT
±1500
Corner pins (SYNC, VDD,
PGOOD, ILIM, VIN, UVLO,
ENABLE)
±750
Other pins
±500
V
AEC Q100-002 indicates HBM stressing is done in accordance with the ANSI/ESDA/JEDEC JS-001 specification.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
VIN
4
Input voltage
4.5
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NOM
MAX
60
UNIT
V
Copyright © 2012–2014, Texas Instruments Incorporated
Product Folder Links: TPS40170-Q1
TPS40170-Q1
www.ti.com
SLVSB90B – JANUARY 2012 – REVISED DECEMBER 2014
6.4 Thermal Information
TPS40170-Q1
THERMAL METRIC
RGY
UNIT
20 PINS
RθJA
Junction-to-ambient thermal resistance
35.4
RθJC(top)
Junction-to-case(top) thermal resistance
38.1
RθJB
Junction-to-board thermal resistance
10.8
ψJT
Junction-to-top characterization parameter
0.5
ψJB
Junction-to-board characterization parameter
10.9
RθJC(bot)
Junction-to-case(bottom) thermal resistance
4.3
°C/W
6.5 Electrical Characteristics
These specifications apply for –40ºC ≤ TA ≤ +125ºC, VVIN = 12 V, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
60
V
1
2.5
µA
4.5
mA
100
mV
INPUT SUPPLY
VVIN
Input voltage range
ISD
Shutdown current
VENABLE < 100 mV
4.5
IQQ
Operating current, drivers not
switching
VENABLE ≥ 2 V, fSW = 300 kHz
ENABLE
VDIS
ENABLE pin voltage to disable
the device
VEN
ENABLE pin voltage to enable
the device
IENABLE
ENABLE pin source current
600
mV
300
nA
8.0
8.3
V
110
200
mV
8-V AND 3.3-V REGULATORS
VVBP
8-V regulator output voltage
VENABLE ≥ 2 V, 8.2 V < VVIN ≤ 60 V,
0 mA < IIN < 20 mA
VDO
8-V regulator dropout voltage,
VVIN-VVBP
4.5 < VVIN ≤ 8.2 V, VEN ≥ 2 V,
IIN = 10 mA
VVDD
3.3-V regulator output voltage
VENABLE ≥ 2 V, 4.5 V < VVIN ≤ 60 V,
0 mA < IIN < 5 mA
3.22
3.3
3.42
V
7.8
FIXED AND PROGRAMMABLE UVLO
VUVLO
Programmable UVLO ON voltage
(at UVLO pin)
VENABLE ≥ 2 V
878
900
919
mV
IUVLO
Hysteresis current out of UVLO
pin
VENABLE ≥ 2 V , UVLO pin > VUVLO
4.06
5
6.2
µA
VBPON
VBP turnon voltage
VBPOFF
VBP turnoff voltage
VBPHYS
VBP UVLO Hysteresis voltage
VENABLE ≥ 2 V, UVLO pin > VUVLO
3.85
4.4
3.6
4.05
180
400
V
mV
REFERENCE
VREF
Reference voltage (+ input of the
error amplifier)
TJ = 25°C, 4.5 V < VVIN ≤ 60 V
594
600
606
–40°C ≤ TJ ≤ 125ºC, 4.5 V < VVIN ≤ 60 V
591
600
609
Range (typical)
100
mV
OSCILLATOR
fSW
Switching frequency
VVALLEY
Valley voltage
KPWM (1)
PWM gain (VVIN / VRAMP)
(1)
600
RRT = 100 kΩ, 4.5 V < VVIN ≤ 60 V
90
100
110
RRT = 31.6 kΩ, 4.5 V < VVIN ≤ 60 V
270
300
330
RRT = 14.3 kΩ, 4.5 V < VVIN ≤ 60 V
540
600
660
0.7
1
1.2
V
14
15
16
V/V
4.5 V < VVIN ≤ 60 V
kHz
Not production tested.
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Electrical Characteristics (continued)
These specifications apply for –40ºC ≤ TA ≤ +125ºC, VVIN = 12 V, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
VVIN = 4.5 V, fSW = 300 kHz
100
150
VVIN = 12 V, fSW = 300 kHz
75
100
UNIT
PWM AND DUTY CYCLE
tON(min) (1)
Minimum controlled pulse
tOFF(max) (1)
Minimum OFF time
DMAX (1)
Maximum duty cycle
ns
VVIN = 60 V, fSW = 300 kHz
50
80
VVIN = 12V, fSW = 300 kHz
170
250
ns
7
10
13
MHz
80
90
95
dB
fSW = 100 kHz, 4.5 V < VVIN ≤ 60 V
95%
fSW = 300 kHz, 4.5 V < VVIN ≤ 60 V
91%
fSW = 600 kHz, 4.5 V < VVIN ≤ 60 V
82%
ERROR AMPLIFIER
(2)
GBWP
AOL
(2)
Gain bandwidth product
Open-loop gain
IIB
Input bias current
100
IEAOP
Output source current
VVFB = 0 V
2
mA
nA
IEAOM
Output sink current
VVFB = 1 V
2
mA
PROGRAMMABLE SOFT START
ISS(source,start)
Soft-start source current
VSS < 0.5 V, VSS = 0.25 V
42
52
62
µA
ISS(source,normal)
Soft-start source current
VSS > 0.5 V, VSS = 1.5 V
9.3
11.6
13.9
µA
ISS(sink)
Soft-start sink current
VSS = 1.5 V
0.77
1.05
1.33
µA
VSS(fltH)
SS pin HIGH voltage during fault
(OC or thermal) reset timing
2.38
2.5
2.61
V
VSS(fltL)
SS pin LOW voltage during fault
(OC or thermal) reset timing
235
300
375
mV
VSS(steady_state)
SS pin voltage during steadystate
3.25
3.3
3.5
V
VSS(offst)
Initial offset voltage from SS pin
to error amplifier input
525
650
775
mV
0
600
mV
TRACKING
VTRK(ctrl) (2)
Range of TRK which overrides
VREF
4.5 V < VIN ≤ 60 V
SYNCHRONIZATION (MASTER/SLAVE)
VMSTR
M/S pin voltage in master mode
3.9
VIN
V
VSLV(0)
M/S pin voltage in slave 0º mode
1.25
1.75
V
VSLV(180)
M/S pin voltage in slave 180º
mode
0
0.75
V
ISYNC(in)
SYNC pin pulldown current
8
14
µA
VSYNC(in_high)
SYNC pin input high-voltage level
2
VSYNC(in_low)
SYNC pin input low-voltage level
tSYNC(high_min)
Minimum SYNC high pulse
duration
tSYNC(low_min)
Minimum SYNC low pulse
duration
(2)
6
M/S configured as slave- 0º or
slave-180º
11
V
0.8
V
40
50
ns
40
50
ns
Not production tested.
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SLVSB90B – JANUARY 2012 – REVISED DECEMBER 2014
Electrical Characteristics (continued)
These specifications apply for –40ºC ≤ TA ≤ +125ºC, VVIN = 12 V, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
1.37
2.64
4
Ω
1.08
2.4
4
Ω
1.37
2.4
4
Ω
0.44
1.1
1.7
Ω
GATE DRIVERS
RHDHI
High-side driver pullup resistance
RHDLO
High-side driver pulldown
resistance
RLDHI
Low-side driver pullup resistance
RLDLO
Low-side driver pulldown
resistance
tNON-OVERLAP1
Time delay between HDRV fall
and LDRV rise
tNON-OVERLAP2
Time delay between HDRV rise
and LDRV fall
CLOAD = 2.2 nF, IDRV = 300 mA, TA = –40°C
to 125°C
50
CLOAD = 2.2 nF,
VHDRV = 2 V, VLDRV = 2 V
ns
60
OVERCURRENT PROTECTION (LOW-SIDE MOSFET SENSING)
4.5 V < VIN < 60 V, TA = 25°C
9
4.5 V < VIN < 60 V, TA = –40°C to 125°C
7
IILIM
ILIM pin source current
IILIM,(ss)
ILIM pin source current during
soft-start
IILIM, Tc (2)
Temperature coefficient of ILIM
current
4.5 V < VIN < 60 V
VILIM (2)
ILIM pin voltage operating range
4.5 V < VIN < 60 V
OCPTH
Overcurrent protection threshold
(voltage across low-side FET for
detecting overcurrent)
RILIM = 10 kΩ, IILIM = 10 µA
(VILIM = 100 mV)
4.5 V < VIN < 60 V, TA = 25°C
4.5 V < VIN < 60 V, TA = –40°C to 125°C
9.75
10.45
12
15
7
12
1400
50
–110
µA
µA
ppm
300
mV
–100
–84
mV
300
360
mV
SHORT CIRCUIT PROTECTION HIGH-SIDE MOSFET SENSING)
VLDRV(max)
AOC3
LDRV pin maximum voltage
during calibration
RLDRV = open
RLDRV = 10 kΩ
Multiplier factor to set the SCP
based on OCP level setting at the RLDRV = open
ILIM pin
RLDRV = 20 kΩ
AOC7
AOC15
2.75
3.2
3.6
V/V
6.4
7.25
7.91
V/V
13.9
16.4
18
V/V
155
165
175
°C
125
135
145
°C
THERMAL SHUTDOWN
TSD,set
(3)
Thermal shutdown set threshold
TSD,reset (3)
Thermal shutdown reset
threshold
Thyst (3)
Thermal shutdown hysteresis
4.5 V < VVIN < 60 V
30
°C
POWER GOOD
VOV
FB pin voltage upper limit for
power good
627
647
670
VUV
FB pin voltage lower limit for
power good
527
552
570
VPG,HYST
Power good hysteresis voltage at
FB pin
8.5
20
32
VPG(out)
PGOOD pin voltage when FB pin
voltage > VOV or < VUV, IPGD = 2
mA
VPG(np)
PGOOD pin voltage when device
power is removed
VVIN is open, 10-kΩ to VEXT = 5 V
VDFWD
Bootstrap diode forward voltage
I = 20 mA
RBOOT-SW
Discharge resistor from BOOT to
SW
4.5 V < VVIN < 60 V
mV
100
mV
1
1.5
V
0.7
0.9
V
BOOT DIODE
(3)
0.5
1
MΩ
Not production tested.
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6.6 Typical Characteristics
600.0
100.0
VIN = 4.5 V
VIN = 24 V
VIN = 60 V
99.5
Switching Frequency (kHz)
Reference Voltage (mV)
599.8
599.5
599.2
599.0
598.8
99.0
98.5
98.0
97.5
97.0
96.5
96.0
95.5
598.5
−40 −25 −10
5
20 35 50 65
Temperature (°C)
80
95
fSW= 100 kHz
95.0
−40 −25 −10 5
20 35 50 65 80
Junction Temperature (°C)
110 125
Figure 1. Reference Voltage vs Junction Temperature
Switching Frequency (kHz)
298
296
294
292
290
288
286
284
Switching Frequency (kHz)
VIN = 4.5 V
VIN = 24 V
VIN = 60 V
282
fSW= 300 kHz
280
−40 −25 −10 5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 3. Switching Frequency vs Junction Temperature
110 125
Figure 2. Switching Frequency vs Junction Temperature
302
300
95
606
602
598
594
590
586
582
578
574
570
566
562
558
fSW= 600 kHz
554
−40 −25 −10 5
20 35 50 65 80
Junction Temperature (°C)
VIN = 4.5 V
VIN = 24 V
VIN = 60 V
95
110 125
Figure 4. Switching Frequency vs Junction Temperature
1.4
3.28
3.26
Operating Current (mA)
Shutdown Current (µA)
1.3
1.2
1.1
1.0
VIN = 12 V
0.9
−40 −25 −10
5
20 35 50 65
Temperature (°C)
80
95
110 125
Figure 5. Shutdown Current vs Junction Temperature
8
3.24
3.22
3.20
3.18
3.16
3.14
VIN = 12 V
fSW = 300 kHz
3.12
3.10
−40 −25 −10
5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 6. Operating Current vs Junction Temperature
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Typical Characteristics (continued)
898.0
5.16
5.14
UVLO Hysteresis Current (µA)
UVLO On Voltage (mV)
897.5
897.0
896.5
896.0
895.5
5.12
5.10
5.08
5.06
5.04
5.02
5.00
895.0
−40 −25 −10
5
20 35 50 65 80
Junction Temperature (°C)
95
4.98
−40 −25 −10
110 125
Figure 7. UVLO On Voltage vs Junction Temperature
VBP UVLO Hysteresis Voltage (mV)
VBP Turn−On Voltage (V)
4.13
4.12
4.11
4.10
4.09
5
20 35 50 65 80
Junction Temperature (°C)
95
325
320
315
310
305
300
295
290
285
280
275
−40 −25 −10
110 125
Figure 9. VBP Turnon Voltage vs Junction Temperature
5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 10. VBP UVLO Hysteresis Voltage
53.00
Soft−Start Source Current (µA)
11.84
Soft−Start Source Current (µA)
110 125
330
4.14
11.80
11.76
11.72
11.68
11.64
52.75
52.50
52.25
52.00
51.75
51.50
51.25
VSS > 0.5 V
11.60
−40 −25 −10
95
Figure 8. UVLO Hysteresis Current vs Junction Temperature
4.15
4.08
−40 −25 −10
5
20 35 50 65 80
Junction Temperature (°C)
5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 11. Soft-Start Source Current vs Junction
Temperature
VSS < 0.5 V
51.00
−40 −25 −10
5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 12. Soft-Start Source Current vs Junction
Temperature
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11.1
680
10.8
674
Soft−Start Initial Offset Voltage (mV)
ILIM Source Current (µA)
Typical Characteristics (continued)
10.5
10.2
9.9
9.6
9.3
9.0
8.7
8.4
−40 −25 −10
5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 13. ILIM Source Current vs Junction Temperature
668
662
656
650
644
638
632
626
620
614
−40 −25 −10
5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 14. Soft-Start Initial Offset Voltage vs Junction
Temperature
Power Good Threshold Voltage (mV)
675
650
625
Overvoltage
Undervoltage
600
575
550
525
−40 −25 −10
5
20 35 50 65 80
Junction Temperature (°C)
95
110 125
Figure 15. VOV/VUV Power Good Threshold Voltage
10
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7 Detailed Description
7.1 Overview
The TPS40170-Q1 device is a synchronous PWM buck controller that accepts a wide range of input voltages
from 4.5 V to 60 V and features voltage-mode control with input-voltage feed-forward compensation. The
switching frequency is programmable from 100 kHz to 600 kHz.
The TPS40170-Q1 device has a complete set of system protections such as programmable UVLO,
programmable overcurrent protection (OCP), selectable short-circuit protection (SCP), and thermal shutdown.
The ENABLE pin allows for system shutdown in a low-current (1-µA typical) mode. The controller supports prebiased outputs, provides an open-drain PGOOD signal, and has closed-loop programmable soft-start, outputvoltage tracking, and adaptive dead-time control.
The TPS40170-Q1 device provides accurate output voltage regulation within 1% accuracy.
Additionally, the controller implements a novel scheme of bidirectional synchronization with one controller acting
as the master and other downstream controllers acting as slaves, synchronized to the master in-phase or 180°
out-of-phase. Slave controllers can be synchronized to an external clock within ±30% of the internal switching
frequency.
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7.2 Functional Block Diagram
ENABLE
VIN
UVLO
1
19
20
TPS40170
8-V
Regulator
VBP
Input and
Regulators OK
Run
3.3-V
Regulator
Gate Drivers
VDD 10
RT
4
SYNC
2
M/S
3
TRK
6
Oscillator
and
Synchronization
8
AGND
9
16 SW
PWM Logic
Anti-Cross
Conduction
RAMP
+
15 VBP
PWM
Comparator
Run
+
+
+
7
COMP
17 HDRV
CLK
SSEAMP
VREF
FB
18 BOOT
VBP
VIN
Error
Amplifier
14 LDRV
Run
13 PGND
Fault
Run
Run
TJ
Over-Temperature
Fault Controller
CLK
VIN
LDRV
CLK
T_FAULT
Power Good
Controller
11 PGOOD
FAULT
Run
Run
FAULT
Reset
SW
ILIM 12
FB
VREF
Soft-Start
and
Fault Logic
Overcurrent
Fault Controller
OC_FAULT
5
SS
SSEAMP
Run
Run
UDG-09218
7.3 Feature Description
7.3.1 LDO Linear Regulators and Enable
The TPS40170-Q1 device has two internal low-dropout (LDO) linear regulators. One has a nominal output
voltage of VVBP and is present at the VBP pin. This is the voltage that is mainly used for the gate-driver output.
The other linear regulator has an output voltage of VVDD and is present at the VDD pin. This voltage can be used
in external low-current logic circuitry. The maximum allowable current drawn from the VDD pin must not exceed
5 mA.
12
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Feature Description (continued)
The TPS40170-Q1 device has a dedicated device-enable pin (ENABLE). This simplifies user-level interface
design because no multiplexed functions exist. If the ENABLE pin of the TPS40170-Q1 device is higher than
VEN, then the LDO regulators are enabled. To ensure that the LDO regulators are disabled, the ENABLE pin
must be pulled below VDIS. By pulling the ENABLE pin below VDIS, the device is completely disabled and the
current consumption is very low (nominally, 1 μA). Both LDO regulators are actively discharged when the
ENABLE pin is pulled below VDIS. A functionally equivalent circuit to the enable circuitry on the TPS40170-Q1
device is shown in Figure 16.
VIN
19
TPS40170
Always Active
ISD= 1 mA
ENABLE
1
+
DISABLE
+
VDIS
AGND
9
UDG-09147
Figure 16. TPS40170-Q1 ENABLE Functional Block
The ENABLE pin must not be allowed to float. If the ENABLE function is not needed for the design, then it is
suggested that the ENABLE pin be pulled up to VIN by a high-value resistor, ensuring that the current into the
ENABLE pin does not exceed 10 μA. If it is not possible to meet this clamp current requirement, then it is
suggested that a resistor divider from VIN to GND be used to connect to ENABLE pin. The resistor divider should
be such that the ENABLE pin is higher than VEN and lower than 8 V.
7.3.2 Input Undervoltage Lockout (UVLO)
The TPS40170-Q1 device has both fixed and programmable input undervoltage lockout (UVLO). In order for the
device to turn ON, all of the following conditions must be met:
• The ENABLE pin voltage must be greater than VEN.
• The VBP voltage (at VBP pin) must be greater than VVBP(on).
• The UVLO pin must be greater than VUVLO.
In order for the device to turn OFF, any one of the following conditions must be met:
• The ENABLE pin voltage must be less than VDIS.
• The VBP voltage (at the VBP pin) must be less than VVBP(off).
• The UVLO pin must be less than VUVLO.
Programming the input UVLO can be accomplished using the UVLO pin. A resistor divider from the input voltage
(VIN pin) to GND sets the UVLO level. Once the input voltage reaches a value that meets the VUVLO level at the
UVLO pin, then a small hysteresis current, IUVLO at the UVLO pin is switched in. The programmable UVLO
function is shown in Figure 17.
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Feature Description (continued)
VIN
TPS40170
IUVLO
R1
UVLO
+
20
R2
VIN_OK
1 nF
+
VUVLO
AGND
9
UDG-09199
Figure 17. UVLO Functional Block Schematic
7.3.3 Equations for Programming the Input UVLO
Components R1 and R2 represent external resistors for programming UVLO and hysteresis; their values can be
calculated in Equation 1 and Equation 2, respectively.
V - VOFF
R1 = ON
IUVLO
(1)
VUVLO
R2 = R1 ´
(VON - VUVLO )
where
•
•
•
•
VON is the desired turnon voltage of the converter.
VOFF is the desired turnoff voltage for the converter.
IUVLO is the hysteresis current generated by the device, 5 µA (typical).
VUVLO is the UVLO pin threshold voltage, 0.9 V (typical).
(2)
NOTE
If the UVLO pin is connected to a voltage greater than 0.9 V, the programmable UVLO is
disabled and the device defaults to an internal UVLO (VVBP(on) and VVBP(off)). For example,
the UVLO pin can be connected to VDD or the VBP pin to disable the programmable
UVLO function.
A 1-nF ceramic bypass capacitor must be connected between the UVLO pin and GND.
7.3.4 Overcurrent Protection and Short-Circuit Protection (OCP and SCP)
The TPS40170-Q1 device has the capability to set a two-level overcurrent protection. The first level of
overcurrent protection (OCP) is the normal overload setting based on low-side MOSFET voltage sensing. The
second level of protection is the heavy overload setting, such as short-circuit based, on the high-side MOSFET
voltage sensing. This protection takes effect immediately. The second level is termed short-circuit protection
(SCP).
14
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Feature Description (continued)
The OCP level is set by the ILIM pin voltage. A current (IILIM) is sourced into the ILIM pin from which a resistor
RILIM is connected to GND. Resistor RILIM sets the first level of overcurrent limit. The OCP is based on the lowside FET voltage at the switch-node (SW pin) when LDRV is ON after a blanking time, which is the product of
inductor current and low-side FET turnon resistance RDS(on). The voltage is inverted and compared to ILIM pin
voltage. If it is greater than the ILIM pin voltage, then a 3-bit counter inside the device increments the fault-count
by 1 at the start of the next switching cycle. Alternatively, if it is less than the ILIM pin voltage, then the counter
inside the device decrements the fault-count by 1. When the fault-count reaches 7, an overcurrent fault
(OC_FAULT) is declared and both the HDRV and LDRV are turned OFF. Resistor RILIM can be calculated by
Equation 3.
IOC ´ RDS(on) IOC ´ RDS(on)
RILIM =
=
IILIM
9.0 mA
(3)
The SCP level is set by a multiple of the ILIM pin voltage. The multiplier has three discrete values, 3, 7, or 15
times, which can be selected by choosing a 10-kΩ, open-circuit, or 20-kΩ resistor, respectively, from the LDRV
pin to GND. This multiplier AOC information is translated during the tCAL time, which starts after the enable and
UVLO conditions are met.
The SCP is based on sensing the high-side FET voltage drop from VVIN to VSW when HDRV is ON after a
blanking time, which is product of inductor current and high-side FET turnon resistance RDS(on). The voltage is
compared to the product of the multiplier and the ILIM pin voltage. If the voltage exceeds the product, then the
fault-count is immediately set to 7 and the OC_FAULT is declared. HDRV is terminated immediately without
waiting for the duty cycle to end. When an OC_FAULT is declared, both the HDRV and LDRV are turned OFF.
The appropriate multiplier (A), can be selected using Equation 4.
ISC ´ RDS(on)HS
A=
IOC ´ RDS(on)LS
(4)
Figure 18 is a functional block diagram of the two-level overcurrent protection.
A
10
3
OPEN
7
20
15
HDRV On
tBLNK
VIN
(A x VILIM)
3-Bit
State
Machine
+
+
RLDRV (kW)
19
HDRV
R
tBLNK
17
LDRV On
SW
R
Q0
OC_FAULT
+
Q1
Q2
16
+
LDRV
VDD
14
CLK
RLDRV
IILIM
ILIM
12
RILIM
PGND
13
UDG-09198
Figure 18. OCP and SCP Protection Functional Block Diagram
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Feature Description (continued)
NOTE
Both OCP and SCP are based on low-side and high-side MOSFET voltage sensing at the
SW node. Excessive ringing on the SW node can have a negative impact on the accuracy
of OCP and SCP. Adding an R-C snubber from the SW node to GND helps minimize the
potential impact.
7.3.5 Oscillator and Voltage Feed-Forward
TPS40170-Q1 device implements an oscillator with input-voltage feed-forward compensation that enables instant
response to input voltage changes. Figure 19 shows the oscillator timing diagram for the TPS40170-Q1 device.
The resistor from the RT pin to GND sets the free-running oscillator frequency. Voltage VRT on the RT pin is
made proportional to the input voltage (see Equation 5).
VIN
VRT =
KPWM
where
•
K = 15
(5)
The resistor at the RT pin sets the current in the RT pin. The proportional current charges an internal 100-pF
oscillator capacitor. The ramp voltage on this capacitor is compared with the RT pin voltage, VRT. Once the ramp
voltage reaches VRT, the oscillator capacitor is discharged. The ramp that is generated by the oscillator (which is
proportional to the input voltage) acts as voltage feed-forward ramp to be used in the PWM comparator.
The time between the start of the discharging oscillator capacitor and the start of the next charging cycle is fixed
at 170 ns (typical). During the fixed discharge time, the PWM output is maintained as OFF. This is the minimum
OFF-time of the PWM output.
VIN
Minimum OFF Time
RAMP
VCOMP
VCLK
PWM
t – Time
UDG-09200
Figure 19. Feed-Forward Oscillator Timing Diagram
7.3.5.1 Calculating the Timing Resistance (RRT)
æ 104
RRT = ç
ç fSW
è
ö
÷ - 2 (kW )
÷
ø
where
•
•
16
fSW is the switching frequency in kHz.
RRT is the resistor connected from RT pin to GND in kΩ.
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Feature Description (continued)
7.3.6 Feed-Forward Oscillator Timing Diagram
NOTE
The switching frequency can be adjusted between 100 kHz and 600 kHz. The maximum
switching frequency before skipping pulses is determined by the input voltage, output
voltage, FET resistances, DCR of the inductor, and the minimum on-time of the
TPS40170-Q1 device. Use Equation 7 to determine the maximum switching frequency.
For further details, see application note SLYT293.
fSW (max ) =
)
(
VOUT(min ) + IOUT(min ) ´ (RDS2 + RLOAD )
)
(
tON(min ) ´ VIN(max ) - IOUT(min ) ´ (RDS1 - RDS2 )
where
•
•
•
•
•
•
•
fSW(max) is the maximum switching frequency.
VOUT(min) is the minimum output voltage.
VIN(max) is the maximum input voltage.
IOUT(min) is the minimum output current.
RDS1 is the high-side FET resistance.
RDS2 is the low-side FET resistance.
RLOAD is the inductor series resistance.
(7)
7.3.7 Soft-Start and Fault-Logic
A capacitor from the SS pin to GND defines the SS time, tSS. The TPS40170-Q1 device enters into soft-start
immediately after completion of the overcurrent calibration. The SS pin goes through the internal level-shifter
circuit of the device before reaching one of the positive inputs of the error amplifier. The SS pin must reach
approximately 0.65 V before the input to the error amplifier begins to rise above 0 V. To charge the SS pin from 0
V to 0.65 V faster, an extra charging current (40.4 µA, typical.) is switched-in to the SS pin at the beginning of
the soft-start in addition to the normal charging current (11.6 µA, typical.). As the SS capacitor reaches 0.5 V, the
extra charging current is turned off and only the normal charging current remains. Figure 20 shows the soft-start
function block.
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Feature Description (continued)
TPS40170
VDD
40.4 mA
11.6 mA
SS
Soft-Start
Charge/Discharge
Control
5
CSS
0.875 mA
VDD
VOUT
TRK
SS_EAmp
R1
+
+
+
VREF
FB
7
SS Error
Amplifier
COMP
FB
R2
UDG-09202
Figure 20. Soft-Start Schematic Block
As the SS pin voltage approaches 0.65 V, the positive input to the error amplifier begins to rise (see Figure 21).
The output of the error amplifier (the COMP pin) starts rising. The rate of rise of the COMP voltage is mainly
limited by the feedback-loop compensation network. Once VCOMP reaches the Vvalley of the PWM ramp, the
switching begins. The output is regulated to the error amplifier input through the FB pin in the feedback loop.
Once the FB pin reaches the 600-mV reference voltage, the feedback node is regulated to the reference voltage,
VREF. The SS pin continues to rise and is clamped to VDD.
The SS pin is discharged through an internal switch during the following conditions:
• Input (VIN) undervoltage lock out UVLO pin less than VUVLO
• Overcurrent protection calibration time (tCAL)
• VBP less than threshold voltage (VBP(off))
Because it is discharged through an internal switch, the discharging time is relatively fast compared with the
discharging time during the fault restart, which is discussed in the Soft-Start During Overcurrent Fault section.
18
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Feature Description (continued)
Internal Logic RUN
Clamped at VDD
SS
tCAL
SS_EAMP
1.1 V
0.5 V
VREF = 0.6 V
0.65 V
VSS
tSS
VVALLEY
VCOMP
(2)
(1)
VOUT
t – Time
UDG-09203
Figure 21. Soft-Start Waveforms
NOTE
Referring to Figure 21:
(1) VREF dominates the positive input of the error amplifier.
(2) SS_EAMP dominates the positive input of the error amplifier.
For 0 < VSS_EAMP < VREF
VOUT = VSS(EAMP) ´
(R1 + R2 )
R2
(8)
For VSS_EAMP > VREF
VOUT = VREF ´
(R1 + R2 )
R2
(9)
7.3.7.1 Soft-Start During Overcurrent Fault
The soft-start block also has a role to control the fault-logic timing. If an overcurrent fault (OC_FAULT) is
declared, the soft-start capacitor is discharged internally through the device by a small current ISS(sink) (1.05 µA,
typical). Once the SS pin capacitor is discharged to below VSS(flt,low) (300 mV, typical), the soft-start capacitor
begins charging again. If the fault is persistent, a fault is declared which is determined by the overcurrentprotection state machine. If the soft-start capacitor is below VSS(flt,high) (2.5 V, typical), then the soft-start capacitor
continues to charge until it reaches VSS(flt,high) before a discharge cycle is initiated. This ensures that the re-start
time-interval is always constant. Figure 22 shows the restart timing.
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Feature Description (continued)
Persistent FAULT
OC_FAULT
FAULT Reset
FAULT Set
tRS
2.5 V
300 mV
VSS
t – Time
UDG-09204
Figure 22. Overcurrent Fault Restart Timing
NOTE
For the feedback to be regulated to the SS_EAMP voltage, the TRK pin must be pulled
high directly or through a resistor to VDD.
7.3.7.2 Equations for Soft-Start and Restart Time
The soft-start time (tSS) is defined as the time taken for the internal SS_EAMP node to go from 0 V to the 0.6-V
VREF voltage. SS_EAMP starts rising as the SS pin goes beyond 0.65 V. The offset voltage between SS and
SS_EAMP starts increasing as the SS pin voltage starts rising. Figure 21 shows that the SS time can be defined
as the time taken for the SS pin voltage to change by 1.05 V (see Equation 10).
t
CSS = SS
0.09
(10)
The restart time (tRS) is defined in Equation 11 as the time taken for the soft-start capacitor (CSS) to discharge
from 2.5 V to 0.3 V and to then recharge up to 2.5 V.
tRS » 2.28 ´ CSS
where
•
•
•
CSS is the soft-start capacitance in nF
tSS is the soft-start time in ms
tRS is the restart time in ms
(11)
NOTE
During soft-start (VSS < 2.5 V), the overcurrent protection limit is 1.5 times the normal
overcurrent protection limit. This allows a higher output capacitance to charge fully without
activating overcurrent protection.
7.3.8 Overtemperature Fault
Figure 23 shows the over temperature protection scheme. If the junction temperature of the device reaches the
thermal shutdown limit of tSD(set) (165°C, typical) and SS charging is completed, an overtemperature FAULT is
declared. The soft-start capacitor begins to be discharged. During soft-start discharging period, the PWM
switching is terminated; therefore, both HDRV and LDRV are driven low, turning off both MOSFETs.
20
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Feature Description (continued)
The soft-start capacitor begins to charge and an overtemperature fault is reset whenever the soft-start capacitor
is discharged below VSS(flt,low) (300 mV, typical). During each restart cycle, PWM switching is turned on. When SS
is fully charged, PWM switching is terminated. These restarts repeat until the temperature of the device has
fallen below the thermal reset level, tSD(reset) (135°C typical). PWM switching continues and the system returns to
normal regulation.
Persistent FAULT
TS_FAULT
FAULT Reset
FAULT Set
tRS
2.5 V
300 mV
VSS
t – Time
UDG-09205
Figure 23. Overtemperature Fault Restart Timing
The soft-start timing during an overtemperature fault is the same as the soft-start timing during an overcurrent
fault. See the Equations for Soft-Start and Restart Time section.
7.3.9 Tracking
The TRK pin is used for output voltage tracking. The output voltage is regulated so that the FB pin equals the
lowest of the internal reference voltage (VREF) or the level-shifted SS pin voltage (SSEAMP) or the TRK pin
voltage. Once the TRK pin goes above the reference voltage, then the output voltage is no longer governed by
the TRK pin, but it is governed by the reference voltage.
If the voltage tracking function is used, then it should be noted that the SS pin capacitor must remain connected
to SS pin and is also used for FAULT timing. For proper tracking using the TRK pin, the tracking voltage should
be allowed to rise only after SSEAMP has exceeded VREF, so that there is no possibility of the TRK pin voltage
being higher than the SSEAMP voltage. From Figure 21, for SSEAMP = 0.6 V, the SS pin voltage is typically 1.7 V.
The maximum slew rate on the TRK pin should be determined by the output capacitance and feedback loop
bandwidth. A higher slew rate can possibly trip overcurrent protection.
Figure 24 shows the tracking functional block. For SSEAMP voltages greater than TRK pin voltage, the VOUT is
given by Equation 12 and Equation 13.
For 0 V < VTRK < VREF
VOUT = VTRK ´
(R1 + R2 )
R2
(12)
For VTRK > VREF
VOUT = VREF ´
(R1 + R2 )
R2
(13)
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Feature Description (continued)
TPS40170
TRK
TRK
TRK IN
6
VOUT
SSEAMP
R1
+
+
+
FB
COMP
VREF
7
FB
R2
UDG-09208
Figure 24. Tracking Functional Block
There are three potential applications for the tracking function.
• Simultaneous voltage tracking
• Ratiometric voltage tracking
• Sequential start-up mode
The tracking function configurations and waveforms are shown in Figure 25, Figure 26, Figure 27, Figure 28,
Figure 29, and Figure 30 respectively.
In simultaneous voltage tracking, shown in Figure 25, tracking signals VTRK1 and VTRK2 of two modules, POL1
and POL2, start up at the same time, and their output voltages VOUT1initial and VOUT2initial are approximately
the same during initial startup. Because VTRK1 and VTRK2 are less than VREF (0.6 V, typical), Equation 12 is
used. As a result, components selection should meet Equation 14.
ææ
ö
ö
R1
çç
÷
÷
æ (R3 + R 4 ) ö
æ (R1 + R2 ) ö
÷
R5 ç çè (R1 + R2 ) ÷ø
=ç
- 1÷
÷ ´ VTRK2 Þ
ç
÷ ´ VTRK1 = ç
ç
÷
ç
÷
R1
R3
R6 ç æ
ö ÷
R3
è
ø
è
ø
ç çç (R + R ) ÷÷ ÷
4 ø
èè 3
ø
(14)
After the lower output voltage setting reaches the output-voltage VOUT1 set point, where VTRK1 increases above
VREF, the output voltage of the other one (VOUT2) continues increasing until it reaches its own set point, where
VTRK2 increases above VREF. At that time, Equation 13 is used. As a result, the resistor settings should meet
Equation 15 and Equation 16.
æ (R1 + R2 ) ö
VOUT1 = ç
÷ ´ VREF
ç
÷
R1
è
ø
(15)
æ (R3 + R 4 ) ö
VOUT2 = ç
÷ ´ VREF
ç
÷
R3
è
ø
(16)
Equation 14 can be simplified into Equation 17 by substituting terms from Equation 15 and Equation 16.
æ R5 ö æ æ VOUT2 ö ö
ç
÷ = çç ç
÷ - 1÷÷
è R6 ø è è VOUT1 ø ø
22
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Feature Description (continued)
If 5-V VOUT2 and 2.5-V VOUT1 are required, according to Equation 15, Equation 16, and Equation 17, the selected
components can be as follows:
• R5 = R6 = R4 = R2 =10 kΩ
• R1 = 3.16 kΩ
• R3 = 1.37 kΩ
VIN
External
Tracking
Input
VTRK1
VOUT1
VTRK1
POL1
R2
VTRK2
0.6
Voltage
R1
R5
VIN
VOUT2
VOUT2
VTRK2
POL2
VOUT1
R4
R6
R3
0
t – Time
UDG-09210
UDG-09209
Figure 25. Simultaneous Voltage-Tracking
Schematic
Figure 26. Simultaneous Voltage-Tracking
Waveform
In ratiometric voltage tracking as shown in Figure 27, the two tracking voltages, VTRK1 and VTRK2, for two
modules, POL1 and POL2, are the same. Their output voltages, VOUT1 and VOUT2, are different with different
voltage dividers, R2–R1 and R4–R3. VOUT1 and VOUT2 increase proportionally and reach their output voltage
set points at approximately the same time.
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Feature Description (continued)
VIN
VTRK2
VOUT1
VTRK1
VTRK1
POL1
0.6
R2
External
Tracking
Input
Voltage
R1
VIN
VOUT2
VOUT2
VTRK2
POL2
VOUT1
R4
R3
0
t – Time
UDG-09212
UDG-09211
Figure 27. Ratiometric Voltage-Tracking Schematic
Figure 28. Ratiometric Voltage-Tracking Waveform
Sequential start-up is shown in Figure 29. During start-up of the first module, POL1, its PGOOD1 is pulled to low.
Because PGOOD1 is connected to soft-start SS2 of the second module, POL2, is not able to charge its soft-start
capacitor. After output voltage VOUT1 of POL1 reaches its setting point, PGOOD1 is released. POL2 starts
charging its soft-start capacitor. Finally, output voltage VOUT2 of POL2 reaches its setting point.
VIN
VOUT1
VOUT1
VSS2, VPGOOD1
PGOOD1
POL1
R2
Voltage
R1
VIN
VOUT2
VOUT2
SS2
POL2
VPGOOD2
R4
CSS
R3
0
t – Time
UDG-09214
UDG-09213
Figure 29. Sequential Start-Up Schematic
24
Figure 30. Sequential Start-Up Waveform
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Feature Description (continued)
NOTE
The TRK pin has high impedance, so it is a noise-sensitive terminal. If the tracking
function is used, a small R-C filter is recommended at the TRK pin to filter out highfrequency noise.
If the tracking function is not used, the TRK pin must be pulled up directly or through a
resistor (with a value between 10 kΩ and 100 kΩ) to VDD.
7.3.10 Adaptive Drivers
The drivers for the external high-side and low-side MOSFETs are capable of driving a gate-to-source voltage,
VVBP. The LDRV driver for the low-side MOSFET switches between VBP and PGND, while the HDRV driver for
the high-side MOSFET is referenced to SW and switches between BOOT and SW. The drivers have nonoverlapping timing that is governed by an adaptive delay circuit to minimize body-diode conduction in the
synchronous rectifier.
7.3.11 Start-Up Into Pre-Biased Output
The TPS40170-Q1 device contains a circuit to prevent current from being pulled out of the output during startup,
in case the output is pre-biased. When the soft-start commands a voltage higher than the pre-bias level (internal
soft-start becomes greater than feedback voltage [VVFB]), the controller slowly activates synchronous rectification
by starting the first LDRV pulses with a narrow on-time (see Figure 31), where:
• VIN = 5 V
• VOUT = 3.3 V
• VPRE = 1.4 V
• fSW = 300 kHz
• L = 0.6 µH
LDRV pulses then increments the on-time on a cycle-by-cycle basis until it coincides with the time dictated by
(1 – D), where D is the duty cycle of the converter. This scheme prevents the initial sinking of the pre-bias output,
and ensures that the output voltage (VOUT) starts and ramps up smoothly into regulation and the control loop is
given time to transition from pre-biased startup to normal mode operation with minimal disturbance to the output
voltage. The time from the start of switching until the low-side MOSFET is turned on for the full (1 – D) interval is
between approximately 20 and 40 clock cycles.
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Feature Description (continued)
Figure 31. Start-Up Switching Waveform During Pre-Biased Condition
If the output is pre-biased to a voltage higher than the voltage commanded by the reference, then the PWM
switching does not start.
NOTE
When output is pre-biased at VPREBIAS, that voltage also applies to the SW node during
start-up. When the pre-bias circuitry commands the first few high-side pulses before the
first low-side pulse is initiated, the gate voltage for the high-side MOSFET is as described
in Equation 18. Alternatively, if the pre-bias level is high, it is possible that SCP can be
tripped due to high the turnon resistance of the high-side MOSFET with low gate voltage.
Once tripped, the device resets and then attempts to restart. The device may not be able
to start up until the output is discharged to a lower voltage level either by an active load or
through feedback resistors.
In the case of a high pre-bias level, a low gate-threshold-voltage-rated device is
recommended for the high-side MOSFET, and increasing the SCP level also helps
alleviate the problem.
VGATE(hs ) =
(VBP -
VDFWD - VPRE-BIAS )
where
•
•
•
26
VGATE(hs) is the gate voltage for the high-side MOSFET.
VBP is the BP regulator output.
VDFWD is bootstrap diode forward voltage.
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Feature Description (continued)
7.3.12 Power Good (PGOOD)
The TPS40170-Q1 device provides an indication that the output voltage of the converter is within the specified
limits of regulation as measured at the FB pin. The PGOOD pin is an open-drain signal and pulls low when any
condition exists which would indicate that the output of the supply might be out of regulation. These conditions
include:
• VVFB is not within the PGOOD threshold limits.
• Soft-start is active, that is, the SS pin voltage is below VSS,FLT,HIGH limit.
• An undervoltage condition exists for the device.
• An overcurrent or short-circuit fault is detected.
• An overtemperature fault is detected.
Figure 32 shows a situation where no fault is detected during the start-up, (the normal PGOOD situation). It
shows that PGOOD goes high tPGD (20 µs, typical) after all the conditions (previously listed) are met.
VDD
Track
VSS, steady-state
VSS, FLT, HI
VSS
VOV
VUV
VFB
tPGD
VPGOOD
t – Time
UDG-09215
Figure 32. PGOOD Signal
When there is no power to the device, PGOOD is not able to pull close to GND if an auxiliary supply is used for
the power-good indication. In this case, a built-in resistor connected from drain to gate on the PGOOD pulldown
device allows the PGOOD pin to operate as a diode to GND.
7.3.13 PGND and AGND
NOTE
The TPS40170-Q1 device provides separate signal ground (AGND) and power ground
(PGND) pins. PGND is primarily used for gate-driver ground return. AGND is an internal
logic-signal ground return. These two ground signals are internally loosely connected by
two anti-parallel diodes. PGND and AGND must be electrically connected externally.
7.3.14 Bootstrap Capacitor
A bootstrap capacitor with a value between 0.1 µF and 0.22 µF must be placed between the BOOT pin and the
SW pin. It should be 10 times higher than MOSFET gate capacitance.
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Feature Description (continued)
7.3.15 Bypass and Filtering
In an integrated circuit, supply bypassing is important for jitter-free operation. To decrease noise in the converter,
ceramic bypass capacitors must be placed as close to the package as possible.
• VIN to GND: use a 0.1-µF ceramic capacitor
• BP to GND: use a 1-µF to 10-µF ceramic capacitor. It should be 10 times greater than the bootstrap
capacitance
• VDD to GND: use a 0.1-μF to 1-µF ceramic capacitor
7.4 Device Functional Modes
7.4.1 Frequency Synchronization
The TPS40170-Q1 device has three modes.
• Master mode: In this mode, the master- or slave-selector pin, (M/S) is connected to VIN. The SYNC pin
emits a stream of pulses at the same frequency as the PWM switching frequency. The pulse stream at the
SYNC pin is of 50% duty cycle and the same amplitude as VVBP. Also, the falling edge of the voltage on
SYNC pin is synchronized with the rising edge of HDRV.
• Slave–180° mode: In this mode, the M/S pin is connected to GND. The SYNC pin of the TPS40170-Q1
device accepts a synchronization clock signal, and HDRV is synchronized with the rising edge of the
incoming synchronization clock.
• Slave–0° mode: In this mode, the M/S pin is left open. The SYNC pin of the TPS40170-Q1 device accepts a
synchronization clock signal, and HDRV is synchronized with the falling edge of the incoming synchronization
clock.
The two slave modes can be synchronized to an external clock through the SYNC pin. They are shown in
Figure 33. The synchronization frequency should be within ±30% of its programmed free-running frequency.
28
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Device Functional Modes (continued)
Master Mode (SYNC as an output pin)
VHDRV
VSYNC
t – Time
Slave 180 Mode (SYNC as an input pin)
VSYNC
VHDRV
t – Time
Slave 0 Mode (SYNC as an input pin)
VSYNC
VHDRV
t – Time
UDG-09206
Figure 33. Frequency Synchronization Waveforms in Different Modes
TPS40170-Q1 device provides a smooth transition for the SYNC clock-signal loss in slave mode. In slave mode,
a synchronization clock signal is provided externally through the SYNC pin to the device. The switching
frequency is synchronized to the external SYNC clock signal. If for some reason the external clock signal is
missing, the device switching frequency is automatically overridden by a transition frequency which is 0.7 times
its programmed free-running frequency. This transition time is approximately 20 μs. After that, the device
switching frequency is changed to its programmed free-running frequency. Figure 34 shows this process.
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Device Functional Modes (continued)
SYNC clock pulse missing
VSYNC
VHDRV
Synchronized duration
fS = SYNC clock frequency
20-ms transition duration
Free running duration .
fS = 0.7 x running frequency
fS = free running frequency
UDG-09207
Figure 34. Transition for SYNC Clock Signal Missing (for Slave–180º Mode)
NOTE
When the device is operating in the master mode with duty ratio around 50%, PWM
jittering may occur. Always configure the device into the slave mode by either connecting
the M/S pin to GND or leaving it floating if master mode is not used.
When the external SYNC clock signal is used for synchronization, limit the maximum slew
rate of the clock signal to 10 V/µs to avoid potential PWM jittering,and connect the SYNC
pin to the external clock signal via a 5-kΩ resistor.
30
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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 should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The wide-input TPS40170-Q1 controller can function in a very wide range of applications. This example
describes the design process for a very wide-input (10 V to 60 V) to regulated 5-V output at a load current of 6 A.
8.2 Typical Application
+
Figure 35. Design Example Application
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Typical Application (continued)
8.2.1 Design Requirements
The design parameters are provided in Table 1.
Table 1. Design Example Parameters
PARAMETER
TEST CONDITIONS
MIN
NOM
10
MAX
VIN
Input voltage
VIN(ripple)
Input ripple
IOUT = 6 A
VOUT
Output voltage
0 A ≤ IOUT ≤ 20 A
Line regulation
10 V ≤ VIN ≤ 60 V
0.5%
Load regulation
0 A ≤ IOUT ≤ 6 A
0.5%
VRIPPLE
Output ripple
IOUT = 6 A
VOVER
Output overshoot
ΔIOUT = 2.5 A
VUNDER
Output undershoot
ΔIOUT = -2.5 A
IOUT
Output current
10 V ≤ VIN ≤ 60 V
tSS
Soft-start time
VIN = 24 V
ISCP
Short circuit current trip point
η
Efficiency
fSW
Switching frequency
4.8
5
UNIT
60
V
0.5
V
5.2
V
100
250
mV
250
mV
0
6
4
A
ms
8
VIN = 24 V, IOUT = 6 A
mV
A
94%
300
Size
kHz
1.5
in2
8.2.2 Detailed Design Procedure
Table 2. Design Example List of Materials
REFERENCE
DESIGNATOR
C1
QTY
4
VALUE
2.2 µF
DESCRIPTION
SIZE
PART NUMBER
MANUF
Capacitor, ceramic, 100-V, X7R, 15%
1210
Std
Std
KZE63VB121M10X16LL
Chemi-con
C6
1
120 µF
Capacitor, aluminum, 63-V, 20%, KZE
series
0.315
inch
(0.8
cm)
C7
1
0.1 µF
Capacitor, ceramic, 50-V, X7R, 15%
603
Std
Std
C9
2 ea
22 µF
10 µF
Capacitor, ceramic, 16-V, X7R, 15%
1210
Std
Std
C13
1
8200 pF
Capacitor, ceramic, 50-V, X7R, 15%
603
Std
Std
C14
1
220 pF
Capacitor, ceramic, 50-V, X7R, 15%
603
Std
Std
C15
1
47 nF
Capacitor, ceramic, 50-V, X7R, 15%
603
Std
Std
C16
1
1 µF
Capacitor, 16-V, X7R, 15%
603
Std
Std
C17
1
1000 pF
Capacitor, ceramic, 50-V, X7R, 15%
603
Std
Std
C18
1
1 µF
Capacitor, ceramic, 100-V, X7R, 15%
1206
Std
Std
C19
1
4.7 µF
Capacitor, ceramic, 16-V, X5R, 15%
805
Std
Std
C21
1
1500 pF
Capacitor, ceramic, 50-V, X7R, 15%
603
Std
Std
Inductor, SMT, 10-A, 16-mΩ
0.51
inch2
(1.3
cm2)
IHLP5050FDER8R2M01
Vishay
L1
1
Q1
1
MOSFET, N-channel, 60-V, 50-A, 11-mΩ
BSC110N06NS3G
Infineon
Q2
1
MOSFET, N-channel, 60-V, 50-A, 7.6-mΩ
BSC076N06NS3G
Infineon
R10
1
2.74 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
R4
1
3.83 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
R5
1
10.0 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
R9
1
12.1 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
32
8.2 µH
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Table 2. Design Example List of Materials (continued)
REFERENCE
DESIGNATOR
QTY
VALUE
DESCRIPTION
SIZE
PART NUMBER
MANUF
R11
1
20.0 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
R6
1
22.1 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
R7
1
31.6 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
R2
1
200 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
R13
1
511 kΩ
Resistor, chip, 1/16W, 1%
603
Std
R603
TPS40170-Q1RGY
Texas
Instruments
IC, 4.5 V–60 V wide input sync. PWM buck
controller
U1
8.2.2.1 Select A Switching Frequency
To maintain acceptable efficiency and meet minimum on-time requirements, a 300-kHz switching frequency is
selected.
8.2.2.2 Inductor Selection (L1)
Synchronous buck power inductors are typically sized for approximately 20%–40% of peak-to-peak ripple current
(IRIPPLE). Given this target ripple current, the required inductor size can be calculated in Equation 19.
VIN(max ) - VOUT
V
1
60 V - 5 V 5 V
1
L»
´ OUT ´
=
´
´
= 8.5 mH
0.3 ´ IOUT
VIN(max ) fSW
0.3 ´ 6 A 60 V 300kHz
(19)
Selecting a standard 8.2-µH inductor value, solving for IRIPPLE = 1.86 A.
The rms current through the inductor is approximated by Equation 20.
2
IL(rms ) =
(I ( ) ) +
L avg
2
1 ´ I
RIPPLE
12
(
)
=
(IOUT )2 + 112 ´ (IRIPPLE )2
=
(6 )2 + 112 ´ (1.86 )2
= 6.02 A
(20)
8.2.2.3 Output Capacitor Selection (C9)
The selection of the output capacitor is typically driven by the output transient response. Equation 21 and
Equation 22 overestimate the voltage deviation to account for delays in the loop bandwidth and can be used to
determine the required output capacitance:
2
VOVER
(ITRAN ) ´ L
I
I
I
´L
< TRAN ´ DT = TRAN ´ TRAN
=
COUT
COUT
VOUT
VOUT ´ COUT
(21)
2
(ITRAN ) ´ L
I
I
I
´L
VUNDER < TRAN ´ DT = TRAN ´ TRAN
=
COUT
COUT (VIN - VOUT ) (VIN - VOUT )´ COUT
(22)
If VIN(min) > 2 × VOUT, use overshoot to calculate minimum output capacitance. If VIN(min) < 2 × VOUT, use
undershoot to calculate minimum output capacitance.
2
COUT(min )
(ITRAN(max) ) ´ L = (3 )2 ´ 8.2 mH = 59 mF
=
VOUT ´ VOVER
5 ´ 250mV
(23)
With a minimum capacitance, the maximum allowable ESR is determined by the maximum ripple voltage and is
approximated by Equation 24.
æ
ö
IRIPPLE
æ
ö
1.86 A
VRIPPLE(tot) - ç
÷ 100mV - ç
÷
VRIPPLE(tot) - VRIPPLE(cap)
8
C
f
´
´
OUT
SW ø
è
è 8 ´ 59 mF ´ 300kHz ø = 47mW
ESRMAX =
=
=
IRIPPLE
IRIPPLE
1.86 A
(24)
Two 1210, 22-µF, 16-V X7R ceramic capacitors plus two 0805 10-µF, 16-V X7R ceramic capacitors are selected
to provide more than 59 µF of minimum capacitance (including tolerance and dc bias derating) and less than
47 mΩ of ESR (parallel ESR of approximately 4 mΩ).
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8.2.2.4 Peak Current Rating of Inductor
With output capacitance, it is possible to calculate the charge current during start-up and determine the minimum
saturation-current rating for the inductor. The start-up charging current is approximated by Equation 25.
´ COUT 5 V ´ (2 ´ 22 mF + 2 ´ 10 mF )
V
=
= 0.08 A
ICHARGE = OUT
tSS
4ms
IL(peak ) = IOUT(max) + (
1
2 ´ IRIPPLE
)+ ICHARGE = 6 A +
1
2 ´ 1.86 A
(25)
+ 0.08 A = 7.01A
(26)
An IHLP5050FDER8R2M01 8.2-µH capacitor is selected. This 10-A, 16-mΩ inductor exceeds the minimum
inductor ratings in a 13-mm × 13-mm package.
8.2.2.5 Input Capacitor Selection (C1, C6)
The input voltage ripple is divided between capacitance and ESR. For this design, VRIPPLE(cap) = 400 mV and
VRIPPLE(ESR) = 100 mV. The minimum capacitance and maximum ESR are estimated by:
ILOAD ´ VOUT
6A´5V
=
= 25 mF
CIN(min) =
VRIPPLE(cap) ´ VIN ´ fSW
400mV ´ 10 V ´ 300kHz
(27)
ESRMAX =
VRIPPLE(esr)
ILOAD + 12 ´ IRIPPLE
=
100mV
= 14.4mW
6.93A
(28)
The rms current in the input capacitors is estimated in Equation 29.
IRMS(cin ) = ILOAD ´ D ´ (1 - D ) = 6 A ´ 0.5 ´ (1 - 0.5) = 3.0 A
(29)
To achieve these values, four 1210, 2.2-µF, 100-V, X7R ceramic capacitors plus a 120-µF electrolytic capacitor
are combined at the input. This provides a smaller size and overall cost than 10 ceramic input capacitors or an
electrolytic capacitor with the ESR required.
Table 3. Inductor Summary
PARAMETER
VALUE
UNIT
L
Inductance
8.2
µH
IL(rms)
RMS current (thermal rating)
6.02
A
IL(peak)
Peak current (saturation rating)
7.01
A
8.2.2.6 MOSFET Switch Selection (Q1, Q2)
Using the J/K method for MOSFET optimization, apply Equation 30 through Equation 33.
High-side gate (Q1):
ö
Q
-9 æ V ´ I
J = (10 ) ´ ç IN OUT + G ´ VDRIVE ÷ ´ fSW
QSW
è IDRIVE
ø
(
)
(W nC)
æV
ö
2
2
-3
K = (10 ) (IOUT ) + 112 ´ (IP-P ) ´ ç OUT ÷ W
mW
è VIN ø
(
)
(30)
(31)
Low-side gate (Q2):
-3
K = (10 )
((I
OUT
)2 + 112 ´ (IP-P )2
)´ æçè1- VV ö÷ø (W mW)
OUT
IN
æ V ´I
ö
Q
J = 10-9 ç FD OUT + G ´ VDRIVE ÷ ´ fSW W
nC
QSW
è IDRIVE
ø
(
)
(32)
(33)
Optimizing for 300 kHz, 24-V input, 5-V output at 6 A, calculate ratios of 5.9 mΩ/nC and 0.5 mΩ/nC for the highside and low-side FETS, respectively. BSC110N06NS2 (ratio 1.2) and BSC076N06NS3 (ratio 0.69) MOSFETS
are selected.
34
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8.2.2.7 Timing Resistor (R7)
The switching frequency is programmed by the current through RRT to GND. The RRT value is calculated using
Equation 34.
RRT =
(10 )4
fSW
- 2kW =
(10 )4
300kHz
- 2 = 31.3kW » 31.6kW
(34)
8.2.2.8 UVLO Programming Resistors (R2, R6)
The UVLO hysteresis level is programmed by R2 using Equation 35.
VUVLO(on ) - VUVLO(off ) 9 V - 8 V
RUVLO(hys ) =
=
= 200kW
IUVLO
5.0 mA
(35)
VUVLO(max)
0.919 V
RUVLO(set ) > RUVLO(hys )
= 200kW
= 22.7kW » 22.1kW
(9.0 V - 0.919 V )
VUVLO _ ON(min) - VUVLO(max)
(
)
(36)
8.2.2.9 Bootstrap Capacitor (C7)
To ensure proper charging of the high-side FET gate, limit the ripple voltage on the boost capacitor to less than
250 mV.
QG1
25nC
=
= 100nF
CBOOST =
VBOOT(ripple ) 250mV
(37)
8.2.2.10 VIN Bypass Capacitor (C18)
Place a capacitor with a value of 1 µF. Select a capacitor with a value between 0.1 µF and 1.0 µF, X5R or better
ceramic bypass capacitor for VIN as specified in Table 2 . For this design, a 1.0-µF, 100 V, X7R capacitor has
been selected.
8.2.2.11 VBP Bypass Capacitor (C19)
Select a capacitor with a value between 1 µF and 10 µF, X5R or better ceramic bypass capacitor for BP as
specified in Table 2. For this design a 4.7-µF, 16 V capacitor has been selected.
8.2.2.12 SS Timing Capacitor (C15)
The soft-start capacitor provides a smooth ramp of the error-amplifier reference voltage for controlled start-up.
The soft-start capacitor is selected by using Equation 38.
t
4ms
CSS = SS =
= 44nF » 47nF
0.09 0.09
(38)
8.2.2.13 ILIM Resistor (R19, C17)
The TPS40170-Q1 controller uses the negative drop across the low-side FET at the end of the OFF time to
measure the inductor current. Allowing for 30% over the minimum current limit for transient recovery and a 20%
rise in RDS(on)Q2 for self-heating of the MOSFET, the voltage drop across the low-side FET at the current limit is
given by Equation 39.
((
) (
VOC = 1.3 ´ IOCP(min) + 21 ´ IRIPPLE
))´ 1.25 ´ RDS(on)G2 = (1.3 ´ 8 A + 21 ´ 1.86 A) ´ 1.25 ´ 7.6mW = 107.6mV
(39)
The internal current-limit temperature coefficient helps compensate for the MOSFET RDS(on) temperature
coefficient, so the current-limit programming resistor is selected by Equation 40.
VOC
107.6mV
=
= 12.0kW » 12.1kW
RILIM =
IOCSET(min )
9.0 mA
(40)
A 1000-pF capacitor is placed in parallel to improve noise immunity of the current-limit set-point.
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8.2.2.14 SCP Multiplier Selection (R5)
The TPS40170-Q1 controller uses a multiplier (AOC) to translate the low-side overcurrent protection into a highside RDS(on) pulse-by-pulse short-circuit protection. Ensure that Equation 41 is true.
1 ´I
RDS(on )Q1 8 A + 1 ´ 1.86 A 11 mW
(
2 RIPPLE )
2
´
=
´
= 1.45
A OC >
IOCP(min) + (21 ´ IRIPPLE ) RDS(on )Q2 8 A + 21 ´ 1.86 A 7.6 mW
IOCP(min) +
(41)
AOC = 3 is selected as the next-greater AOC. The value of R5 is set to 10 kΩ.
8.2.2.15 Feedback Divider (R10, R11)
The TPS40170-Q1 controller uses a full operational amplifier with an internally fixed 0.6-V reference. The value
of R11 is selected between 10 kΩ and 50 kΩ for a balance of feedback current and noise immunity. With the
value of R11 set to 20 kΩ, the output voltage is programmed with a resistor divider given by Equation 42.
VFB ´ R11
0.600 V ´ 20.0kW
R10 =
=
= 2.73kW » 2.74kW
(VOUT - VFB ) (5.0 V - 0.600 V )
(42)
8.2.2.16 Compensation: (R4, R13, C13, C14, C21)
Using the TPS40k Loop Stability Tool for a 60-kHz bandwidth and a 50° phase margin with an R10 value of 20
kΩ, the following values are obtained. The tool is available from the TI Web site, Literature Number SLUC263.
• C21 = C1 = 1500 pF
• C13 = C2 = 8200 pF
• C14 = C3 = 220 pF
• R13 = R2 = 511 Ω
• R4 = R3 = 3.83 kΩ
8.2.3 Application Curves
Figure 36 shows an efficiency graph for this design with 10-V to 60-V input and 5-V at 6-A output. Figure 37
shows a 24-V to 5-V at 6-A loop response, where VIN = 24 V and IOUT = 6 A, yielding 58-kHz bandwidth, 51°
phase margin. Figure 38 shows the output ripple 20 mV/div, 2 µs/div, 20 MHz bandwidth.
100
100
225
80
180
60
135
40
90
20
45
0
0
85
VIN = 10 V
VIN = 12 V
VIN = 24 V
VIN = 36 V
VIN = 48 V
VIN = 60 V
80
75
70
0
1
2
3
4
Load Current (A)
5
−20
−40
−45
−90
Gain
Phase
−60
0.1
6
Figure 36. Efficiency vs Load Current
36
Phase (°)
90
Gain (dB)
Efficiency (%)
95
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1
10
Frequency (kHz)
100
−135
1000
Figure 37. Loop Response
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Figure 38. Output Ripple Waveform
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9 Power Supply Recommendations
9.1 Bootstrap Resistor
A small resistor in series with the bootstrap capacitor reduces the turnon time of the internal MOSFET, thereby
reducing the rising edge ringing of the SW node and reducing shoot-through induced by dv/dt. A bootstrap
resistor value that is too large delays the turnon time of the high-side switch and may trigger an apparent SCP
fault. See the Design Examples section.
9.2 SW-Node Snubber Capacitor
Observable voltage ringing at the SW node is caused by fast switching edges and parasitic inductance and
capacitance. If the ringing results in excessive voltage on the SW node, or erratic operation of the converter, an
R-C snubber may be used to dampen the ringing and ensure proper operation over the full load range. See the
Design Examples section.
9.3 Input Resistor
The TPS40170-Q1 device has a wide input-voltage range, which allows for the device input to share a power
source with the power-stage input. Power-stage switching noise may pollute the device power source if the
layout is not adequate in minimizing noise. Power-stage switching noise may trigger a short-circuit fault. If so,
adding a small resistor between the device input and power-stage input is recommended. This resistor, together
with the device input capacitor, composes an R-C filter that filters out the switching noise from power stage. See
the Design Examples section.
9.4 LDRV Gate Capacitor
Power-device selection is important for proper switching operation. If the low-side MOSFET has low gate
capacitance Cgs (if Cgs < Cgd), there is a risk of short-through induced by high dv/dt at the switching node
during high-side turnon. If this happens, add a small capacitance between LDRV and GND. See the Design
Examples section.
38
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10 Layout
10.1 Layout Guidelines
Figure 39 illustrates an example layout. For the controller, it is important to connect carefully noise-sensitive
signals such as RT, SS, FB, and COMP as close to the IC device as possible and connect to AGND as shown.
The thermal pad should be connected to any internal PCB ground planes using multiple vias directly underneath
the IC device. AGND and PGND should be connected at a single point.
High-performance FETs such as NexFET™ power MOSFETs from Texas Instruments, require careful attention
to the layout. Minimize the distance between the positive node of the input ceramic capacitor and the drain pin of
the control (high-side) FET. Minimize the distance between the negative node of the input ceramic capacitor and
the source pin of the syncronize (low-side) FET. Becasue of the large gate drive, smaller gate charge, and faster
turnon times of the high-performance FETs, use a minimum of four 10-µF ceramic input capacitors such as TDK
#C3216X5R1A106M. Ensure the layout allows a continuous flow of the power planes.
The layout of the HPA578 EVM is shown in Figure 39 through Figure 42 for reference.
10.2 Layout Example
Figure 39. Top Copper, Viewed From Top
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Layout Example (continued)
Figure 40. Bottom Copper, Viewed From Bottom
40
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Layout Example (continued)
Figure 41. Internal Layer 1, Viewed From Top
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Layout Example (continued)
Figure 42. Internal Layer 2, Viewed From Top
42
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11 Device and Documentation Support
11.1 Device Support
11.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
11.2 Documentation Support
11.2.1 Related Documentation
For related documentation see the following:
• Steve Mappus, DV/DT Immunity Improved in Synchronous Buck Converters. July, 2005, Power Electronics
Technology.
• TPS40057 Wide-Input Synchronous Buck Controller SLUS593.
• TPS40k Loop Stability Tool (SLUC263)
11.3 Trademarks
NexFET is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.4 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.
11.5 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.
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43
PACKAGE OPTION ADDENDUM
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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)
TPS40170QRGYRQ1
ACTIVE
VQFN
RGY
20
3000
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-40 to 125
PXXQ
(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