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SM74104
SNOSBA3D – JUNE 2011 – REVISED MAY 2015
SM74104 High Voltage Half-Bridge Gate Driver with Adaptive Delay
1 Features
3 Description
•
•
The SM74104 High Voltage Gate Driver is designed
to drive both the high side and the low side NChannel MOSFETs in a synchronous buck
configuration. The floating high-side driver is capable
of working with supply voltages up to 100V. The high
side and low side gate drivers are controlled from a
single input. Each change in state is controlled in an
adaptive manner to prevent shoot-through issues. In
addition to the adaptive transition timing, an additional
delay time can be added, proportional to an external
setting resistor. An integrated high voltage diode is
provided to charge the high side gate drive bootstrap
capacitor. A robust level shifter operates at high
speed while consuming low power and providing
clean level transitions from the control logic to the
high side gate driver. Under-voltage lockout is
provided on both the low side and the high side
power rails.
1
•
•
•
•
•
•
Renewable Energy Grade
Drives both a High Side and Low Side N-Channel
MOSFET
Adaptive Rising and Falling Edges with
Programmable Additional Delay
Single Input Control
Bootstrap Supply Voltage Range up to 118V DC
Fast Turn-Off Propagation Delay (25 ns Typical)
Drives 1000 pF Loads with 15 ns Rise and Fall
Times
Supply Rail Under-Voltage Lockout
2 Typical Applications
•
•
•
•
Current Fed Push-Pull Power Converters
High Voltage Buck Regulators
Active Clamp Forward Power Converters
Half and Full Bridge Converters
Device Information(1)
PART NUMBER
SM74104
PACKAGE
BODY SIZE (NOM)
WSON (10)
4.0 mm x 4.0 mm
SOIC (8)
4.9 mm x 3.9 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
(Optional external
fast recovery diode)
VIN
VCC
RGATE
HB
VDD
HO
VDD
CBOOT
PWM
CONTROLLER
OUT1
IN
HS
SM74104
OUT2
LO
RT
GND
L
C
VSS
SM74104 Driving MOSFETs Connected in Synchronous Buck Configuration
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.
SM74104
SNOSBA3D – JUNE 2011 – REVISED MAY 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
9
10
11
12
Features ..................................................................
Typical Applications ..............................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
Absolute Maximum Ratings..................................
ESD Ratings ...........................................................
Recommended Operating Conditions .................
Thermal Information..............................................
Electrical Characteristics .....................................
Switching Characteristics ....................................
1
1
1
2
3
4
4
4
4
4
5
6
12.1 Typical Performance Characteristics ...................... 7
13 Detailed Description ........................................... 10
13.2
13.3
13.4
13.5
Functional Block Diagram .....................................
Feature Description...............................................
Device Functional Modes......................................
Power Dissipation Considerations ........................
10
10
12
12
14 Application and Implementation........................ 14
14.1 Application Information.......................................... 14
14.2 Typical Application ............................................... 14
15 Power Supply Recommendations ..................... 16
16 Layout................................................................... 16
16.1 Layout Guidelines ................................................. 16
16.2 Layout Example .................................................... 16
17 Device and Documentation Support ................. 18
17.1 Trademarks ........................................................... 18
17.2 Electrostatic Discharge Caution ............................ 18
17.3 Glossary ................................................................ 18
13.1 Overview ............................................................... 10
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (April 2013) to Revision D
•
Added ESD Ratings table, Thermal Information 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
Changes from Revision B (April 2013) to Revision C
•
2
Page
Page
Changed layout of National Data Sheet to TI format ............................................................................................................. 1
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5 Pin Configuration and Functions
8-Pin SOIC
Package D
Top View
VDD
1
HB
2
8
LO
7
VSS
SOIC-8
HO
3
6
IN
HS
4
5
RT
10-Pin WSON
Package DPR
Top View
VDD
1
10
HB
2
9
VSS
HO
3
8
IN
HS
4
7
RT
NC
5
6
NC
LO
Pin Functions
PIN
NAME
NO.
I/O
DESCRIPTION
D
DPR
VDD
1
1
I
Positive supply voltage input.
HB
2
2
I
Positive connection for high-side bootstrap capacitor.
HO
3
3
O
High-side output to drive the top MOSFET.
HS
4
4
I
Switch node pin.
RT
5
7
I
Delay timer pin. The additional delay of the timer prevents lower and upper
MOSFETs from conducting simultaneously, thereby preventing shoot-through.
Timer delay is set with a resistor to ground.
IN
6
8
I
PWM control input for LO and HO outputs.
VSS
7
9
-
Ground pin.
LO
8
10
O
Low-side output to drive the bottom MOSFET.
N/C
-
5, 6
-
No connect.
Exposed Pad
-
Exposed
Pad
-
The exposed die attach pad (DAP) on the 10-pin WSON package functions as
a thermal connection and can be soldered to a copper plane under the device.
The DAP nas no direct electrical connection to any of the pins. It can be left
floating, but it is recommended to connect this to VSS.
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6 Specifications
7 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1)
MIN
MAX
UNIT
VDD to VSS
–0.3
18
V
VHB to VHS
–0.3
18
V
IN to VSS
–0.3
VDD + 0.3
V
LO Output
–0.3
VDD + 0.3
V
HO Output
VHS – 0.3
VHB + 0.3
V
VHS to VSS
–1
100
V
118
V
VHB to VSS
RT to VSS
–0.3
5
V
Tstg Storage Temperature Range
–55
150
°C
150
°C
Maximum Junction Temperature
(1)
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.
8 ESD Ratings
VALUE
V(ESD)
(1)
Human-body model (HBM), per
ANSI/ESDA/JEDEC JS-001 (1)
Electrostatic discharge
All pins except 2, 3, and 4
±2000
Pins 2, 3, and 4
±500
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 500-V HBM is possible with the necessary precautions.
9 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
VDD
9
14
V
HS
–1
100
V
HB
VHS + 8
VHS + 14
V
50
V/ns
125
°C
HS Slew Rate
Junction Temperature
–40
10 Thermal Information
SM74104
THERMAL METRIC (1)
D
DPR
8 PINS
10 PINS
RθJA
Junction-to-ambient thermal resistance
114.5
37.9
RθJC(top)
Junction-to-case (top) thermal resistance
61.1
38.1
RθJB
Junction-to-board thermal resistance
55.6
14.9
ψJT
Junction-to-top characterization parameter
9.7
0.4
ψJB
Junction-to-board characterization parameter
54.9
15.2
RθJC(bot)
Junction-to-case (bottom) thermal resistance
-
4.4
(1)
4
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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11 Electrical Characteristics
Over operating junction temperature range, VDD = VHB = 12 V, VSS = VHS = 0 V, RT = 100 kΩ, no load on LO or HO, unless
otherwise specified.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY CURRENTS
IDD
VDD Quiescent Current
LI = HI = 0V
0.4
0.6
mA
IDDO
VDD Operating Current
f = 500 kHz
1.9
3
mA
IHB
Total HB Quiescent Current
LI = HI = 0V
0.06
0.2
mA
IHBO
Total HB Operating Current
f = 500 kHz
1.3
3
mA
IHBS
HB to VSS Current, Quiescent
VHS = VHB = 100V
0.05
10
IHBSO
HB to VSS Current, Operating
f = 500 kHz
0.08
µA
mA
INPUT PINS
VIL
Low Level Input Voltage Threshold
VIH
High Level Input Voltage Threshold
RI
Input Pulldown Resistance
0.8
100
1.8
V
1.8
2.2
V
200
500
kΩ
TIME DELAY CONTROLS
VRT
Nominal Voltage at RT
IRT
RT Pin Current Limit
TD1
Delay Timer, RT = 10 kΩ
TD2
Delay Timer, RT = 100 kΩ
6.0
RT = 0V
2.7
3
3.3
V
0.75
1.5
2.25
mA
58
90
130
ns
140
200
270
ns
6.9
7.4
V
UNDER VOLTAGE PROTECTION
VDDR
VDD Rising Threshold
VDDH
VDD Threshold Hysteresis
VHBR
HB Rising Threshold
VHBH
HB Threshold Hysteresis
0.5
5.7
6.6
V
7.1
0.4
V
V
BOOT STRAP DIODE
VDL
Low-Current Forward Voltage
IVDD-HB = 100 µA
0.60
0.9
V
VDH
High-Current Forward Voltage
IVDD-HB = 100 mA
0.85
1.1
V
RD
Dynamic Resistance
IVDD-HB = 100 mA
0.8
1.5
Ω
LO GATE DRIVER
VOLL
Low-Level Output Voltage
ILO = 100 mA
0.25
0.4
V
VOHL
High-Level Output Voltage
ILO = –100 mA
VOHL = VDD – VLO
0.35
0.55
V
IOHL
Peak Pullup Current
VLO = 0V
1.6
A
IOLL
Peak Pulldown Current
VLO = 12V
1.8
A
HO GATE DRIVER
VOLH
Low-Level Output Voltage
IHO = 100 mA
0.25
0.4
V
VOHH
High-Level Output Voltage
IHO = –100 mA,
VOHH = VHB – VHO
0.35
0.55
V
IOHH
Peak Pullup Current
VHO = 0V
1.6
A
IOLH
Peak Pulldown Current
VHO = 12V
1.8
A
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12 Switching Characteristics
Over operating junction temperature range, VDD = VHB = 12 V, VSS = VHS = 0 V, no load on LO or HO, unless otherwise
specified.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
25
56
ns
25
56
ns
tLPHL
Lower Turn-Off Propagation Delay (IN Rising
to LO Falling)
tHPHL
Upper Turn-Off Propagation Delay (IN Falling
to HO Falling)
tRC, tFC
Either Output Rise/Fall Time
CL = 1000 pF
15
ns
tR, tF
Either Output Rise/Fall Time
(3V to 9V)
CL = 0.1 µF
0.6
µs
tBS
Bootstrap Diode Turn-Off Time
IF = 20 mA, IR = 200 mA
50
ns
6
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12.1 Typical Performance Characteristics
100
2.0
VDD = 12V CL = 4400 pF
IDDO
RT = 10k
1.9
10
1.7
CURRENT (mA)
CURRENT (mA)
CL = 1000 pF
CL = 2200 pF
CL = 470 pF
1
1.5
1.3
1.1
CL = 0 pF
IHBO
0.9
0
10
1
100
0.7
-50 -25
1000
0
25
50
75
100 125 150
FREQUENCY (kHz)
TEMPERATURE (°C)
Figure 1. IDD vs Frequency
Figure 2. Operating Current vs Temperature
1.20
1.20
IDD, RT = 10k
1.00
IDD, RT = 10k
CURRENT (mA)
CURRENT (mA)
1.00
0.80
0.60
IDD, RT = 100k
0.40
0.20
0.00
9
0.60
IDD, RT = 100k
0.40
0.20
IHB, RT = 10k, 100k
8
0.80
IHB, RT = 10k, 100k
0.00
-50
10 11 12 13 14 15 16 17 18
-25
0
100000
2.00
VDD = VHB = 12V, HS = 0V
1.60
1.40
CURRENT (A)
CURRENT (PA)
75 100 125 150
1.80
CL = 4400 pF
CL = 2200 pF
10000
50
Figure 4. Quiescent Current vs Temperature
Figure 3. Quiescent Current vs Supply Voltage
HB = 12V,
HS = 0V
25
TEMPERATURE (°C)
VDD, VHB (V)
CL = 1000 pF
1000
1.20
SOURCING
1.00
0.80
SINKING
0.60
100
0.40
CL = 0 pF
10
0.1
0.20
CL = 470 pF
0.00
1
10
100
0
1000
4
6
8
10
12
HO, LO (V)
FREQUENCY (kHz)
Figure 5. IHB vs Frequency
2
Figure 6. HO & LO Peak Output Current vs Output Voltage
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Typical Performance Characteristics (continued)
0.60
1.00E-01
T = 150°C
0.55
1.00E-02
VDDH
HYSTERESIS (V)
T = 25°C
ID (A)
1.00E-03
1.00E-04
0.50
0.45
VHBH
0.40
T = -40°C
1.00E-05
1.00E-06
0.2
0.35
0.3
0.4
0.5
0.6
0.7
0.8
0.30
-50
0.9
-25 0_
25 50_ 75_100_125_150_
TEMPERATURE (oC)
VD (V)
Figure 7. Diode Forward Voltage
Figure 8. Undervoltage Threshold Hysteresis vs
Temperature
0.700
7.30
7.20
0.600
VDD = VHB = 8V
7.00
0.500
VDDR
6.90
VOH (V)
THRESHOLD (V)
7.10
6.80
6.70
VHBR
6.60
VDD = VHB = 12V
0.400
0.300
VDD = VHB = 16V
6.50
0.200
6.40
6.30
-50 -25
0
25
50
0.100
-50 -25
75 100 125 150
0
25
50
75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 9. Undervoltage Rising Threshold vs Temperature
Figure 10. LO & HO Gate Drive—High Level Output Voltage
vs Temperature
0.400
40.0
38.0
0.350
36.0
VDD = VHB = 8V
34.0
DELAY (ns)
VOL (V)
0.300
VDD = VHB = 12V
0.250
0.200
TLPHL
32.0
30.0
28.0
26.0
VDD = VHB = 16V
THPHL
24.0
0.150
22.0
0.100
-50
8
-25
0
25
50
20.0
-50 -25
75 100 125 150
0
25
50
75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 11. LO & HO Gate Drive—Low Level Output Voltage
vs Temperature
Figure 12. Turn Off Propagation Delay vs Temperature
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Typical Performance Characteristics (continued)
120
220
110
100
180
160
80
ad
De
tive )
c
e
Eff + t RT
(t P
,HO
LO Time
70
60
50
40
30
TIME (ns)
TIME (ns)
90
200
LO,HO Turn On
Delay (tD)
0
25
120
LO,HO Turn On
Delay (tD)
100
80
60
LO,HO Turn Off
Delay (tD)
20
-50 -25
LO,HO Effective Dead
Time (tP + tRT)
140
LO,HO Turn Off Delay (tD)
40
50
20
-50 -25
75 100 125 150
0
25
50
75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 13. Timing vs Temperature RT = 10K
Figure 14. Timing vs Temperature RT = 100K
200
VDD = 12V, HB = 12V,
CL = 0, HS = 0
DELAY (ns)
175
150
THPLH
125
TLPLH
100
75
10
20
30
40
50
60
70
80
90 100
RT (k:)
Figure 15. Turn On Delay vs RT Resistor Value
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13 Detailed Description
13.1 Overview
SM74104 is a high voltage, high speed, dual output driver designed to drive top and bottom MOSFETs
connected in synchronous buck or half-bridge configuration. SM74104 also features adaptive delay to prevent
shoot-through current through top and bottom MOSFETs during switching transitions. The outputs that drive the
top and bottom MOSFETs are controlled by one externally provided PWM signal.
13.2 Functional Block Diagram
HV
UVLO
LEVEL
SHIFT
HO
DRIVER
HS
IN
RT
VDD
UVLO
DRIVER
LO
VSS
13.3 Feature Description
13.3.1 PWM Input Control
Referring to the timing diagram in Figure 16, the rising edge of the PWM input (IN) turns off the bottom MOSFET
(LO) after a short propagation delay (tP). An adaptive circuit in the SM74104 monitors the bottom gate voltage
(LO) and triggers a programmable delay generator when the LO pin falls below an internally set threshold (≈
Vdd/2). The gate drive of the upper MOSFET (HO) is disabled until the deadtime expires. The upper gate is
enabled after the TIMER delay (tP+TRT), and the upper MOSFET turns-on. The additional delay of the timer
prevents lower and upper MOSFETs from conducting simultaneously, thereby preventing shoot-through.
10
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Feature Description (continued)
VDD
HB
IN
Adapt
Logic
DLY
Logic
Driver
Adapt
Logic
DLY
Logic
Driver
HO
HS
LO
SM74104
RT
VSS
50%
SM74104
WAVEFORMS
IN
tp+TRT
LO
tp
50%
tp
tp+TRT
50%
HO
Td
Td
Figure 16. Application Timing Waveforms
A falling transition on the PWM signal (IN) initiates the turn-off of the upper MOSFET and turn-on of the lower
MOSFET. A short propagation delay (tP) is encountered before the upper gate voltage begins to fall. Again, the
adaptive shoot-through circuitry and the programmable deadtime TIMER delays the lower gate turn-on time. The
upper MOSFET gate voltage is monitored and the deadtime delay generator is triggered when the upper
MOSFET gate voltage with respect to ground drops below an internally set threshold (≈ Vdd/2). The lower gate
drive is momentarily disabled by the timer and turns on the lower MOSFET after the deadtime delay expires
(tP+TRT).
13.3.2 Setting the Delay Timer with RT
The RT pin is biased at 3V and current limited to 1mA. It is designed to accommodate a resistor between 5K and
100K, resulting in an effective dead-time proportional to RT and ranging from 90ns to 200ns. RT values below 5K
will saturate the timer and are not recommended.
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13.4 Device Functional Modes
13.4.1 Startup and UVLO
Both top and bottom drivers include under-voltage lockout (UVLO) protection circuitry which monitors the supply
voltage (VDD) and bootstrap capacitor voltage (VHB – VHS) independently. The UVLO circuit inhibits each driver
until sufficient supply voltage is available to turn-on the external MOSFETs, and the built-in hysteresis prevents
chattering during supply voltage transitions. When the supply voltage is applied to VDD pin of SM74104, the top
and bottom gates are held low until VDD exceeds UVLO threshold, typically about 6.9V. Any UVLO condition on
the bootstrap capacitor will disable only the high side output (HO).
13.5 Power Dissipation Considerations
The total IC power dissipation is the sum of the gate driver losses and the bootstrap diode losses. The gate
driver losses are related to the switching frequency (f), output load capacitance on LO and HO (CL), and supply
voltage (VDD) and can be roughly calculated as:
PDGATES = 2 • f • CL • VDD2
(1)
There are some additional losses in the gate drivers due to the internal CMOS stages used to buffer the LO and
HO outputs. The following plot shows the measured gate driver power dissipation versus frequency and load
capacitance. At higher frequencies and load capacitance values, the power dissipation is dominated by the
power losses driving the output loads and agrees well with the above equation. This plot can be used to
approximate the power losses due to the gate drivers.
1.000
CL = 4400 pF
CL = 2200 pF
POWER (W)
0.100
CL = 1000 pF
0.010
CL = 470 pF
CL = 0 pF
0.001
0.1
_
1.0
_
10.0_
100.0
1000.0_
SWITCHING FREQUENCY (kHz)
Figure 17. Gate Driver Power Dissipation (LO + HO)
VCC = 12V, Neglecting Diode Losses
The bootstrap diode power loss is the sum of the forward bias power loss that occurs while charging the
bootstrap capacitor and the reverse bias power loss that occurs during reverse recovery. Since each of these
events happens once per cycle, the diode power loss is proportional to frequency. Larger capacitive loads
require more current to recharge the bootstrap capacitor resulting in more losses. Higher input voltages (VIN) to
the half bridge result in higher reverse recovery losses. The following plot was generated based on calculations
and lab measurements of the diode recovery time and current under several operating conditions. This can be
useful for approximating the diode power dissipation.
12
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Power Dissipation Considerations (continued)
1.000
POWER (W)
CL = 4400 pF
0.100
CL = 0 pF
0.010
0.001
1.0 kHz
10.0 kHz
100.0 kHz
1000.0 kHz
SWITCHING FREQUENCY (kHz)
Figure 18. Diode Power Dissipation VIN = 80V
1.000
POWER (W)
CL = 4400 pF
0.100
CL = 0 pF
0.010
0.001
1.0 kHz
10.0 kHz
100.0 kHz
1000.0 kHz
SWITCHING FREQUENCY (kHz)
Figure 19. Diode Power Dissipation VIN = 40V
The total IC power dissipation can be estimated from the above plots by summing the gate drive losses with the
bootstrap diode losses for the intended application. Because the diode losses can be significant, an external
diode placed in parallel with the internal bootstrap diode (refer to Figure 20) can be helpful in removing power
from the IC. For this to be effective, the external diode must be placed close to the IC to minimize series
inductance and have a significantly lower forward voltage drop than the internal diode.
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14 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.
14.1 Application Information
The SM74104 can drive both a high-side and a low-side MOSFET using only one PWM input control signal. The
internal level shifter provides a means for the control input to drive the high-side MOSFET. The SM74104
prevents shoot-through issues through adaptive transition timing and an additional time delay can be added by
use of an external resistor at the RT pin.
14.2 Typical Application
The SM74104 is used to drive MOSFETs connected in a synchronous buck configuration as shown in Figure 20.
A single control signal from an external PWM controller provides the control input to drive both the high-side and
low-side MOSFET. The HO and LO outputs of the SM74104 can provide very fast switching of the MOSFETs,
thereby reducing switching losses and improving the overall efficiency of the system.
(Optional external
fast recovery diode)
VIN
VCC
RGATE
HB
VDD
HO
VDD
CBOOT
PWM
CONTROLLER
OUT1
IN
HS
SM74104
OUT2
LO
RT
GND
L
C
VSS
Figure 20. Typical Application
14.2.1 Design Requirements
The RT resistor should be sized such that the appropriate time delay is added between the switching transitions
of the top and bottom MOSFETs. The exact RT value will depend on the selected MOSFETs, their switching
speeds, and the desired delay time needed to prevent shoot-through. An optional external fast recovery diode
should be placed between the VDD and HB pins to minimize the stress on the internal bootstrap diode and
decrease the average power dissipation in the IC. An RGATE resistor and a parallel diode may also be placed in
the path of the MOSFET gates. The RGATE resistor will decrease the ON switching speed of the MOSFET and
can help damp possible oscillations on the line. The parallel diode will provide a current path around RGATE
during the OFF switching of the MOSFET, which can ensure fast shut off of the MOSFET to further prevent
shoot-through.
14
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Typical Application (continued)
14.2.2 Detailed Design Procedure
See Power Supply Recommendations, Layout, and Power Dissipation Considerations for key design
considerations regarding the input supply, grounding, component placement, and power calculations specific to
the SM74104.
14.2.3 Application Curve
An adaptive circuit in the SM74104 monitors the gate voltages of the top and bottom MOSFETs and triggers a
programmable delay generator to prevent both MOSFETs from conducting simultaneously. The timer delay, TRT,
can be programmed with a resistor placed between RT and VSS. The value of TRT will vary with the RT resistor
value as shown in Figure 21.
200
VDD = 12V, HB = 12V,
CL = 0, HS = 0
DELAY (ns)
175
150
THPLH
125
TLPLH
100
75
10
20
30
40
50
60
70
80
90 100
RT (k:)
Figure 21. Turn On Delay vs RT Resistor Value
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15 Power Supply Recommendations
A low ESR/ESL capacitor must be connected as close as possible to the IC between VDD and VSS pins and
between HB and HS pins to support high peak currents being drawn from VDD during turn-on of the external
MOSFET. Also, to prevent large voltage transients at the drain of the top MOSFET, a low ESR electrolytic
capacitor must be connected between MOSFET drain and ground (VSS). In both cases, the traces should be as
short as possible to reduce the series resistance.
16 Layout
16.1 Layout Guidelines
The optimum performance of high and low side gate drivers cannot be achieved without taking due
considerations during circuit board layout. The following points are emphasized.
1. In order to avoid large negative transients on the switch node (HS) pin, the parasitic inductances in the
source of top MOSFET and in the drain of the bottom MOSFET (synchronous rectifier) must be minimized.
2. Grounding considerations:
– The first priority in designing grounding connections is to confine the high peak currents from charging
and discharging the MOSFET gate in a minimal physical area. This will decrease the loop inductance and
minimize noise issues on the gate terminal of the MOSFET. The MOSFETs should be placed as close as
possible to the gate driver.
– The second high current path includes the bootstrap capacitor, the bootstrap diode, the local ground
referenced bypass capacitor and low side MOSFET body diode. The bootstrap capacitor is recharged on
a cycle-by-cycle basis through the bootstrap diode from the ground referenced VDD bypass capacitor. The
recharging occurs in a short time interval and involves high peak current. Minimizing this loop length and
area on the circuit board is important to ensure reliable operation.
3. The resistor on the RT pin must be placed very close to the IC and separated from high current paths to
avoid noise coupling to the time delay generator which could disrupt timer operation.
16.2 Layout Example
Figure 22 shows an example layout for the SM74104 in the 8-pin SOIC package option.
16
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Layout Example (continued)
Figure 22. SM74104 Layout Example
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17 Device and Documentation Support
17.1 Trademarks
All trademarks are the property of their respective owners.
17.2 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.
17.3 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
18
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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)
SM74104MA/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
74104
MA
SM74104MAX/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
74104
MA
SM74104SD/NOPB
ACTIVE
WSON
DPR
10
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
S74104
SM74104SDX/NOPB
ACTIVE
WSON
DPR
10
4500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
S74104
(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
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