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MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
General Description
Benefits and Features
The MAX20429 is a high-efficiency dual switching regulator that delivers up to 6A (peak) load current per output
from 0.5V to 1.5875V in 12.5mV steps and 1.6V to 3.8V
in 50mV steps. The IC operates from 3V to 5.5V, making
it ideal for on-board point-of-load and post-regulation applications. Total output error is less than ±1.0% over load,
line, and temperature.
● High-Feature Set in an Ultra-Small Footprint
• High-Efficiency DC-DC Converter
• Two Independent Outputs, up to 6A per Output
• 3.0V to 5.5V Operating Supply Voltage
• Resistor-Adjustable Output Voltage
• Optional Factory-Preset Output Voltage
• 2.1MHz/3.2MHz Options
• Enable Input
• Individual RESET Outputs
• Spread-Spectrum Option
• Peak Current-Mode Architecture
• 3mm x 3.5mm FCQFN
The MAX20429 features fixed-frequency PWM mode operation with a switching frequency of 2.1MHz or 3.2MHz.
High-frequency operation allows for an all-ceramic capacitor design with small external components.
The low-resistance on-chip switches ensure high efficiency at heavy loads while minimizing critical inductances,
making the layout a much simpler task with respect to discrete solutions. Following a simple layout and footprint ensures first-pass success in new designs.
The device features the MAXQ™ technology, which provides precision transient performance and phase margin.
This allows obtaining the maximum power, performance,
and precision from the converter over a very wide range of
configurations.
The MAX20429 has separate enable inputs and status
outputs for each buck converter. The output voltage is
preset at the factory to allow customers to achieve ±1%
output-voltage accuracy without using expensive 0.1% resistors. The devices offer factory programmable soft-start
and RESET times.
The devices include over-temperature shutdown and overcurrent limiting. All devices are designed to operate from
–40 °C to +125 °C ambient temperature range.
Applications
● Secondary Regulator for SoC / MCU Supply
19-100842; Rev 1; 12/20
● High-Precision
• 108/92% OV/UV Monitor
• ±3% OV/UV Accuracy
• ±1% Output Voltage Accuracy
• Excellent Load-Transient Performance
• PWM and SKIP Mode Operation
• MAXQTM Power Architecture
● High Efficiency
• Up to 96% Efficiency 5V to 3.3V
• Up to 90% Efficiency 5V to 1V
● -40°C to +125°C Operating Temperature Range
● AEC-Q100 Qualified
Ordering Information appears at end of data sheet.
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Simplified Block Diagram
VIN
PV1,PV2
OUT1
CIN
L
LX1
VIN
VOUT1
COUT
SYNC
PGND1
VDD
MAX20429
GND
OUT2
L
ENABLE 1
EN1
ENABLE 2
EN2
LX2
PGND2
VOUT2
COUT
VIO
PGND
RESET1
RESET2
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Maxim Integrated | 2
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
TABLE OF CONTENTS
General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Simplified Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
FC2QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
MAX20429 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Functional Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Internal Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
MAXQ Power Architecture (No Wasted Performance). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Enable Input (EN1, EN2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
RESET Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Internal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Synchronization (SYNC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Soft-Start and Soft-Shutdown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Current Limit / Short-Circuit Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
PWM/SKIP Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Overtemperature Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Spread Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Resistor-Adjustable Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Input Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Inductor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Output Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Typical Application Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Typical Application Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
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Maxim Integrated | 3
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
LIST OF TABLES
Table 1. Slope Compensation Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 2. Output Capacitor Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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Maxim Integrated | 4
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Absolute Maximum Ratings
PV1, PV2 to GND ....................................................... -0.3V to 6V
VDD to GND................................................................ -0.3V to 6V
OUT1, OUT2 to GND ..................................... -0.3V to VDD+0.3V
LX1, LX2 to GND............................................... -0.3 to PV_ + 0.3
EN1, EN2, RESET1, RESET2 to GND ...................... -0.3V to 6V
SYNC to GND................................................. -0.3V to VDD+0.3V
PGND_ to GND ..................................................... -0.3V to +0.3V
LX Continuous RMS Current (95000hr lifespan) ...................... 4A
LX Continuous RMS Current (15000hr lifespan) ......................6A
Output Short-Circuit Duration......................................Continuous
Continuous Power Dissipation (4-Layer Board) (T A = +70°C,
derate 51.8 mW/°C above +70°C. ) .......................... to 4145mW
Ambient Operating Temperature ........................-40°C to +125°C
Operating Junction Temperature ........................-40°C to +150°C
Storage Temperature Range ..............................-65°C to +150°C
Lead Temperature Range................................................. +300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the
device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
Package Information
FC2QFN
Package Code
F183A3FY+1
Outline Number
21-100428
Land Pattern Number
90-100155
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
19.3°C/W
Junction to Case (θJC)
5.0°C/W
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates
RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal
considerations, refer to www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(PV1 = PV2 = 5V, TJ = -40 °C to +150 °C, unless otherwise noted. Typical values are at TA = 25 °C under normal conditions unless
otherwise noted.)
PARAMETER
SYMBOL
PV Supply Voltage
Range
VPV
Supply Current
IVDD
CONDITIONS
VEN1 = VEN2 = low, TA = +25°C
3
VEN1 = high, VEN2 = low, no load
440
VUVLO
Falling
VDD UVLO
VUVLO
Rising
Spread Spectrum
Range
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fSW
TYP
3.0
VDD UVLO
Oscillator Frequency
MIN
2.4
MAX
UNITS
5.5
V
5
2.6
V
2.7
2.9
fSW = 2.1MHz
1.9
2.1
2.3
fSW = 3.2MHz
2.9
3.2
3.6
+3
µA
V
MHz
%
Maxim Integrated | 5
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Electrical Characteristics (continued)
(PV1 = PV2 = 5V, TJ = -40 °C to +150 °C, unless otherwise noted. Typical values are at TA = 25 °C under normal conditions unless
otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
3.8
V
OUT
Programmable voltage range, 3.0 V ≤
VPV ≤ 5.5V (Note 4)
Output Voltage
Skip Mode Peak Current
VOUT
ISKIP
Voltage Accuracy
DC Load Regulation
DC Line Regulation
High-Side OnResistance
RON-H
Low-Side OnResistance
RON-L
nMOS Zero-Crossing
Threshold
ILIM
12.5
Step size, 1.6 V ≤ VOUT ≤ 3.8 V (Note 4)
50
0.7
0.825
1
Option 2
0.9
1.1
1.3
Option 3
1.15
1.4
1.65
Option 4
1.3
1.69
2
PWM mode, 0A ≤ ILOAD ≤ IMAX,
MAX(3.0V,VOUT + 0.5V) ≤ VIN ≤ 5.5V,
0.6V ≥ VOUT ≥ 3.8V
-1
1
%
PWM mode, 0A ≤ ILOAD ≤ IMAX, 0.5V ≤
VOUT ≤ 0.5875V
-7
+7
mV
PWM mode, 0A ≤ ILOAD ≤ IMAX,
MAX(3.0V,VOUT + 0.5V) ≤ VIN ≤ 5.5V,
VOUT = 0.6V. ADJ variant
MAX20429CAFNA/VY+
-1
+1
%
0A ≤ ILOAD ≤ IMAX (PWM mode)
0.1
PV_ from 3V to 5.5V
0.05
Including metal and package
18
Intrinsic
16
Including metal and package
12
Intrinsic
10
Option 1 (2.0A DC)
2.6
3.5
Option 2 (3.0A DC)
3.9
4.7
Option 3 (4.0A DC)
5.2
6.0
Option 4 (6.0A DC)
7.8
10
%/V
50
50
mΩ
mΩ
%
A
100
mA
PV = 3.3V, IOUT = 2A (Note 4)
1
ns
tDEAD
PV = 3.3V, IOUT = 2A (Note 4)
3
ns
0.01
µA
DMAX
Effective
100
%
Minimum On-Time
tON
35
LX_ Discharge
Resistance
RDIS
50
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A
%
92.4
LX_ Leakage Current
Max Duty Cycle
mV
Option 1
IZX
LX_ Rise/Fall Time
Dead Time
Step size, 0.5 V ≤ VOUT ≤ 1.5875 V (Note
4)
VIN = 5V, VOUT = 1.8V, L = 220nH, DCR
= 13mΩ
Efficiency
Current-Limit Threshold
0.5
60
ns
Ω
Maxim Integrated | 6
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Electrical Characteristics (continued)
(PV1 = PV2 = 5V, TJ = -40 °C to +150 °C, unless otherwise noted. Typical values are at TA = 25 °C under normal conditions unless
otherwise noted.)
PARAMETER
SYMBOL
LX_ Switching Phase
Soft-Start Rate
CONDITIONS
MIN
180
Option 1 (step = 12.5mV for VOUT <
1.6V, otherwise 50mV)
32
Option 2 (step = 12.5mV for VOUT <
1.6V, otherwise 50mV)
16
Option 3 (step = 12.5mV for VOUT <
1.6V, otherwise 50mV)
8
Option 4 (step = 12.5mV for VOUT <
1.6V, otherwise 50mV)
4
tSHDN
UNITS
°
Hi-Z
Option 2 (step = 12.5mV for VOUT <
1.6V, otherwise 50mV)
PWM mode, 0A ≤ ILOAD ≤ IMAX, 0.5V ≤
VOUT ≤ 0.5875V
Voltage Accuracy
MAX
clks/step
Option 1
Soft-Shutdown Rate
TYP
LX1 rising to LX2 rising (Note 4)
32
-7
clks/step
+7
mV
RESET
OV Threshold Range
VOUT Rising
104
108
112
%
UV Threshold Range
VOUT Falling
89
92
95
%
Active Timeout Period
tHOLD
Output Low Level
Option 1 (15.6ms@2.1MHz,
10.2ms@3.2MHz)
32768
Option 2 (7.8ms@2.1MHz,
5.1ms@3.2MHz)
16384
Option 3 (3.9ms@2.1MHz,
2.5ms@3.2MHz)
8192
Option 4 (488μs@2.1MHz,
320μs@3.2MHz)
1024
clks
ISINK = 3mA
0.1
TSHDN
(Note 4)
165
ºC
THYS
(Note 4)
15
ºC
Leakage Current
0.1
µA
OV/UV Filter
10
μs
Thermal Shutdown
Temperature
Thermal Shutdown
Hysteresis
0.2
V
ENABLE INPUT (EN)
Input High
Rising
Input Low
Falling
1.5
V
0.5
V
Hysteresis
0.05
V
Leakage Current
0.1
µA
SYNCHRONIZATION (SYNC)
Input High
Input Low
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1.8
V
0.4
V
Maxim Integrated | 7
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Electrical Characteristics (continued)
(PV1 = PV2 = 5V, TJ = -40 °C to +150 °C, unless otherwise noted. Typical values are at TA = 25 °C under normal conditions unless
otherwise noted.)
PARAMETER
SYNC Input Frequency
Range
Pulldown Resistance
SYMBOL
fSYNC
CONDITIONS
MIN
TYP
MAX
fSW = 2.1MHz
1.8
2.5
fSW = 3.2MHz
2.8
3.6
100
UNITS
MHz
kΩ
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a 4-layer
board. For detailed information on package thermal considerations see http://www.maxim-ic.com/thermal-tutorial.
Note 2: All units are 100% production tested at +25˚C. All temperature limits are guaranteed by design.
Note 3: The device is designed for continuous operation up to TJ = +125°C for 95,000 hours and TJ = +150°C for 5,000 hours.
Note 4: Guaranteed by design. Not production tested.
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Maxim Integrated | 8
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Typical Operating Characteristics
(VPV1 = VPV2 = 5V; TA = +25°C unless otherwise noted)
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Maxim Integrated | 9
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Typical Operating Characteristics (continued)
(VPV1 = VPV2 = 5V; TA = +25°C unless otherwise noted)
Pin Configuration
MAX20429
SYNC
OUT1
17
16
15
14
EN2
1
13
EN1
RESET2
2
12
RESET1
PV2
3
11
PV1
5
6
7
8
PGND2
PGND
PGND1
10
PGND2
4
LX1
9
PGND1
LX2
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VDD
18
GND
OUT2
TOP VIEW
Maxim Integrated | 10
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Pin Description
PIN
NAME
FUNCTION
1
EN2
OUT2 Active-High Enable Input. Drive EN2 HIGH for normal operation. The device enters soft-start
on the rising edge enters soft-shutdown on the falling edge.
2
RESET2
3
PV2
OUT2 Power Input Supply. Connect a 10μF or larger ceramic capacitor from PV2 to PGND2.
4
LX2
OUT2 Inductor Connection. Connect LX2 to the switched side of the inductor.
5,6
PGND2
OUT2 Power Ground
OUT2 Active-Low Open Drain RESET Output. External pullup resistor required if used.
7
PGND
Power Ground
8,9
PGND1
OUT1 Power Ground
10
LX1
OUT1 Inductor Connection. Connect LX1 to the switched side of the inductor.
11
PV1
OUT1 Power Input Supply. Connect a 10μF or larger ceramic capacitor from PV1 to PGND1.
12
RESET1
13
EN1
14
OUT1
OUT1 Feedback Input. Connect to the output capacitor of Output 1.
15
SYNC
SYNC Input. Connect SYNC to GND or leave unconnected to enable skip-mode operation under
light loads. Connect SYNC to PV or an external clock to enable fixed-frequency FPWM operation.
16
VDD
Internal Analog Supply. Connect a 2.2µF capacitor between this pin and GND.
17
GND
Analog Ground
18
OUT2
OUT2 Feedback Input. Connect to the output capacitor of Output 2.
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OUT1 Active-Low Open Drain RESET Output. External pullup resistor required if used.
OUT1 Active-High Enable Input. Drive EN1 HIGH for normal operation. The device enters soft-start
on the rising edge enters soft-shutdown on the falling edge.
Maxim Integrated | 11
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Functional Diagrams
Internal Block Diagram
x2
I-SENSE
AMP
PV1,
PV2
SKIP CURRENT
COMP
CLK
PV_
PEAK CURRENT
COMP
RAMP
GENERATOR
∑
CONTROL
LOGIC
PWM
COMP
LX1,
LX2
PV_
COMP
PGND1
VID[7:0]
I-SENSE
AMP
VREF
EAMP
FPWM CLK
VREF
8-BIT DAC
OV[x]
OUT1,
OUT2
UV[x]
VREF
OV
OV
OV
UV
MAXQTM
TEST LOGIC
UVLO
VDD
ZX
COMP
CLK
CLK180
FPWM
OSC
PGND1,
PGND2
SYNC
PGND
OTP
GND
AGND
UV/OV
EN1
EN2
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CONTROL
LOGIC
BANDGAP
VREF
RESET1
RESET1
RESET1
RESET2
VID[7:0]
RESET2
RESET2
Maxim Integrated | 12
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
Converter
Detailed Description
MAXQ Power Architecture (No Wasted Performance)
The MAXQ power architecture allows the MAX20429 to achieve the maximum dynamic performance under all worst-case
conditions. Without the MAXQ power architecture, typical AC performance must be lowered below the device capabilities
to guarantee that the device will be stable under all worst-case application conditions. The MAXQ power architecture
keeps the device operating at peak performance.
Enable Input (EN1, EN2)
The enable control input EN1/EN2 activates the device channel from its low-power shutdown state. EN1/EN2 have an
input-high threshold of 1.5V (typ), an input-low threshold of 0.5V, and a hysteresis of 50mV (typ). When an enable input
goes high, the output voltage ramps up with the soft-start time. When an enable input goes low, the output voltage ramps
down with the soft-start time or enters a Hi-Z state depending on the factory programmed setting of the device. See SoftStart and Soft-Shutdown section for more detail.
RESET Output
The device features open-drain reset outputs that assert low when the corresponding output voltage is outside of the OV/
UV window. The OV/UV comparators run from a separate reference to provide drift detection on the outputs. RESET_
remains asserted for a fixed timeout period after the corresponding output returns to its regulated voltage. The fixed
timeout period for 2.1 MHz is selectable between 0.5ms, 3.9ms, 7.8ms, or 15.6ms. The fixed timeout period for 3.2 MHz
is selectable between 0.3ms, 2.5ms, 5.1ms, or 10.2ms. To obtain a logic signal, place a pullup resistor between the
RESET_ pins to the system I/O voltage.
Internal Oscillator
The device has a spread-spectrum oscillator that varies the internal operating frequency by ±3% relative to the internally
generated operating frequency of 2.1MHz/3.2MHz (typ). This function does not apply to externally applied oscillation
frequency on the SYNC pin.
Synchronization (SYNC)
A logic-high on SYNC enables fixed-frequency, forced-PWM mode. Apply an external clock on the SYNC input to
synchronize the internal oscillator to an external clock. The SYNC input accepts signal frequencies in the range of
1.9MHz < fSYNC < 2.3MHz when fSW = 2.1MHz, and 2.9MHz < fSYNC < 3.6MHz when fSW = 3.2MHz. When the pin is
open-circuited or logic-low, the SYNC input enables the device to enter a low-power skip mode under light-load conditions
if the IC is configured to allow that behavior.
Soft-Start and Soft-Shutdown
The device includes a factory-programmable fixed soft-start time. Soft-start time limits startup inrush current by forcing
the output voltage to ramp up towards its regulation point. The soft-start ramp rate can be factory programmed with four
different options: 32, 16, 8, or 4 clocks per step, where step size = 12.5mV for VOUT ≤ 1.6V (50mV step size when VOUT
> 1.6V).
When an EN pin goes low, the associated output enters shutdown. There are factory programmable options available that
will either simply disable switching and activate a 50Ω (typ) discharge resistor, or perform a soft-shutdown by ramping
down the reference at a fixed rate until a minimum on-time of 20ns is reached, at which point the switching stops and the
discharge resistor is activated. The soft-shutdown ramp rate is fixed at 32 clocks per step, where step size = 12.5mV for
VOUT ≤ 1.6V (50mV step size when VOUT > 1.6V) when not configured as a simple discharge resistor.
Current Limit / Short-Circuit Protection
The device features a current limit that protects the device against short-circuit and overload conditions at the output. In
the event of a short-circuit or overload condition, the high-side MOSFET remains on until the inductor current reaches
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MAX20429
Dual 6A High-Efficiency Low Voltage Buck
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the high-side MOSFET’s current-limit threshold. The converter then turns on the low-side MOSFET to allow the inductor
current to ramp down. Once the inductor current crosses below the low-side MOSFET current-limit threshold, the
converter turns on the high-side MOSFET again. This cycle repeats until the short or overload condition is removed.
If the device crosses the current limit with the output voltage below 50% of the target, hiccup mode will be enabled and
the output will turn off for 10ms, then the channel will attempt to power up through soft-start.
PWM/SKIP Modes
The device features an input (SYNC) that puts the converter either in SKIP mode or forced-PWM mode of operation.
See Pin Descriptions for mode detail. In FPWM mode of operation, the converter switches at a constant frequency with
variable on-time. In SKIP mode, the converter’s switching frequency is load-dependent until the output load reaches a
set threshold. At higher load current, the switching frequency does not change, and the operating mode is similar to the
FPWM mode. SKIP mode helps improve efficiency in light-load applications by allowing the converter to turn on the highside switch only when the output voltage falls below a set threshold. As such, the converter does not switch MOSFETs
on and off, as is often the case in the PWM mode. Consequently, the gate charge and switching losses are much lower
in SKIP mode.
Overtemperature Protection
Thermal overload protection limits the total power dissipation in the MAX20429. When the junction temperature exceeds
165°C (typ), an internal thermal sensor shuts down both outputs, allowing the IC to cool. The thermal sensor turns on the
outputs again after the junction temperature cools by 15°C.
Spread Spectrum
The spread-spectrum option is enabled/disabled based on the part number. See the ordering table. If the spread
spectrum is enabled and an external clock is applied to the SYNC pin, then the spread-spectrum circuit is bypassed,
effectively disabling the option.
Resistor-Adjustable Output
MAX20429 output voltage can be set by external resistors in addition to the factory programmed VOUT options. See the
Typical Application Diagram for placement of R1 and R2 external resistors. Desired output voltage can be calculated
using the following method:
VOUT =
R1 + R2
* VREF
R2
where VREF = 0.6V when using the device specified for adjustable output voltage.
Fixed output voltage devices can use external resistors to achieve output voltages higher than the factory setting. When
using a fixed output voltage device, use the factory preset output voltage as VREF to calculate the resistor values.
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MAX20429
Dual 6A High-Efficiency Low Voltage Buck
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Applications Information
Input Capacitor Selection
An input filter capacitor reduces peak currents drawn from the upstream power source and reduces noise and voltage
ripple on the input (caused by the circuit's switching behavior). One 10µF X7R ceramic capacitor each is recommended
for the PV1 and PV2 pins. The VDD pin is the input to the analog circuitry and should be connected to the same supply
as PV1/2 through a series 2Ω resistor IC to a 2.2µF X7R bypass capacitor.
Inductor Selection
Three key inductor parameters must be specified for operation with the MAX20429: inductance value (L), peak inductor
current (IPEAK), and inductor saturation current (ISAT). The minimum required inductance is a function of operating
frequency, input-to-output voltage differential, and the maximum output current capability of the output. A lower inductor
value minimizes size and cost, improves large-signal and transient response, but reduces efficiency due to higher
peak currents and higher peak-to-peak output-voltage ripple for the same output capacitor. On the other hand, higher
inductance increases efficiency by reducing the ripple current. Resistive losses due to extra wire turns can exceed the
benefit gained from lower ripple current levels especially when the inductance is increased without also allowing for larger
inductor dimensions.
Soft-saturating inductors are recommended for use with the MAX20429. The gradual decrease in inductance means that
the IC will respond to overcurrent conditions before the LX current reaches dangerously high levels that might otherwise
result in damage to the IC. If a hard-saturating inductor is used, its saturation current must be above the maximum LX
current limit. For a soft-saturation inductor, only the current limit for temperature must be above the maximum LX current
limit.
The MAX20429 is designed for nominal ΔIPK-PK equal to approximately 33% of the full load current. Use the following
equation to calculate the typical inductance with respect to ripple current:
(VIN − VOUT) × VOUT
L = V ×f
IN SW × IMAX × ΔPK − PK
The VIN and VOUT terms are typical values to optimize inductor selection for expected operating conditions. The
switching frequency fSW is 2.1MHz, 3.2MHz, or a different value if the synchronization function is utilized. The maximum
current IMAX is the channel's rated output current (2A, 3A, 4A, or 6A), not the expected application maximum load current.
Calculate the minimum inductance LMIN1 with ΔPK-PK = 40%, and the typical inductance LTYP1 with ΔPK-PK = 30%.
The second bound on minimum inductance is with respect to slope compensation. This applies only to peak current
control, not to adaptive COT control. The absolute minimum inductance allowable must ensure that the inductor current
downslope is less than twice the downslope of the compensation ramp:
m2
−m≥ 2
Table 1. Slope Compensation Terms
TERM
VALUE
VOUT
m2
Inductor current downslope:
-m
Compensating ramp: OTP_SLP * 0.680 V / µsec
OTP_SLP
1/2, 2/3, 4/3 (factory programmed)
L
× RCS
0.330Ω for 2A channel
RCS
0.240Ω for 3A channel
0.185Ω for 4A channel
0.133Ω for 6A channel
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MAX20429
Dual 6A High-Efficiency Low Voltage Buck
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For margin of error, the worst-case inductance (largest derating for current and temperature, plus lowest value for percent
tolerance) should result in the inductor downslope being 25% greater than half the slope compensation ramp:
RCS
LMIN2 = VOUT × 2 × m × 1.25
Nominally, the inductor current down-slope should be approximately equal to the compensating ramp. Equal down-slopes
will result in current waveform perturbations being eliminated in a single switching cycle:
RCS
LTYP2 = VOUT × m
Two equations must therefore be fulfilled: one equation for minimum worst-case inductance (required) and one for typical
inductance (recommended): LMIN > max ( LMIN1 , LMIN2 ) and LTYP > max ( LTYP1 , LTYP2 ). The maximum inductance
should be less than 2 x LTYP2 to avoid degrading the control performance.
Output Capacitors
The MAX20429 is designed to be stable with low-ESR ceramic capacitors. Other capacitor types are not recommended
as the ESR zero can affect stability of the device. The output capacitor calculations below are guidelines based on
nominal conditions. The phase margin must be measured on the final circuit to verify proper stability is achieved.
Conditions:
● Feed-forward zero enabled, GMZ = 116μS, FFR = 300kΩ
● Nominal inductor value based on the Inductor Selection section
For VOUT < 1.6V
RCOMP
COUTMIN = 11.5μsec × IMAX × 140kΩ
RCOMP
COUTTYP = 24.5μsec × IMAX × 140kΩ
For VOUT ≥ 1.6V
RCOMP
COUTMIN = 8.0μsec × IMAX × 140kΩ
RCOMP
COUTTYP = 21.0μsec × IMAX × 140kΩ
Table 2. Output Capacitor Terms
TERM
DESCRIPTION
COUTMIN
Minimum fully-derated capacitance necessary for phase margin of approximately 45 degrees
COUTTYP
Nominal output capacitance for a UGBW of 200kHz
IMAX
The IC channel's maximum DC current capability: 2A, 3A, 4A, or 6A
VOUT
Nominal output voltage
RCOMP
Compensation Resistor setting. Default = 140kΩ. Can be factory set from 35kΩ to 297.5kΩ in 17.5kΩ increments.
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MAX20429
Dual 6A High-Efficiency Low Voltage Buck
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Typical Application Circuits
Typical Application Diagram
VIN
PV1,PV2
OUT1
RESISTOR ADJUSTABLE OUTPUT OPTION
2x10µF
220nH
LX1
VIN 2Ω
VDD
R2
VOUT1
2x47μF
SYNC
PGND1
OUT1
OUT2
LX1
MAX20429
2.2µF
GND
220nH
2x47μF
220nH
LX2
EN1
EN2
VOUT1
R1
PGND1
VOUT2
2x47μF
PGND2
VIO
PGND
RESET1
RESET2
Ordering Information
PART
VOUT1
(V)
MAX20429AAFNA/VY+
MAX20429CAFNA/VY+
VOUT2
(V)
(1)
IOUT2
(A)
(2)
SPREAD
SPECTRUM
(3)
fSW
(MHz)
(4)
tHOLD
(ms)
(5)
Soft-Start
(1)
IOUT1
(A)
(2)
SoftShutdown
RCOMP
(kΩ)
0.85
3
0.72
6
ON
2.1
15.6
1.64 mv/us
0.82 mv/us
122.5
ADJ
(6)
6
ADJ
(6)
6
ON
2.1
3.9
730 us (fixed)
730 us
(fixed)
140
For variants with different options, contact the factory
/V Denotes an AEC-Q100 automotive-qualified part.
+ Denotes lead(Pb)-free/RoHS-compliant package.
T Denotes tape-and-reel.
Y Denotes side-wettable package.
(1) Fixed factory setting, 0.5V to 1.5875V in 12.5mV steps or 1.6V to 3.8V in 50mV steps.
(2) 2, 3, 4, or 6
(3) ON or OFF
(4) 2.1 or 3.2
(5) 0.5, 3.9, 7.8, 15.6 for f
SW = 2.1MHz or 0.3, 2.5, 5.1, 10.2 for fSW = 3.2MHz.
(6) ADJ (adjustable externally)
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Maxim Integrated | 17
MAX20429
Dual 6A High-Efficiency Low Voltage Buck
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Revision History
REVISION
NUMBER
REVISION
DATE
0
6/20
Initial release
12/20
Updated General Description, Benefits and Features, Absolute Maximum Ratings,
Electrical Characteristics, Detailed Description, and Ordering Information
1
PAGES
CHANGED
DESCRIPTION
—
1, 4, 5, 12, 13, 16
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max
limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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