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MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
General Description
Benefits and Features
The MAX77503 is a synchronous 1.5A step-down DCDC converter optimized for portable 2-cell and 3-cell battery-operated and USB-C applications. The converter operates on an input supply between 3V and 14V. Output
voltage is adjustable between 0.8V and 5V in 50mV steps
through an I2C serial interface or 1.55V to 99% of the supply voltage with external feedback resistors. Factory-programmed default voltages of 1.2V, 1.8V, and 3.3V are offered to reduce component count for common rails. The
device features a low-IQ SKIP mode which allows excellent efficiency at light loads.
● 1.5A Single Channel Buck Regulator
● 3V to 14V Input Voltage Range
● 0.8V to 99%VSUP Output Voltage Range
• 0.8V to 5V I2C Programmable in 50mV Steps
• 1.55V to 99%VSUP with External Feedback
Resistors
• 1.2V, 1.8V, or 3.3V Factory Preset Options
● High-Efficiency, Low-IQ Extends Battery Life
• 94% Peak Efficiency at 7.4VSUP, 3.3VOUT (2520
Inductor)
• 9μA IQ (12VSUP, 1.8VOUT Internal Feedback
Version)
• Selectable Light-Load SKIP and Forced-PWM
Modes
Dedicated enable and power-OK pins allow simple hardware control. An I2C serial interface is optionally used for
full configuration and control for dynamic voltage scaling
and system power optimization.
● 1MHz or 550kHz Fixed-Frequency Switching
● Hardware or Software Control
• Enable Input and Power-OK Output Pins
• Optional I2C Full Control Interface
Built-in undervoltage lockout (UVLO), output active discharge, cycle-by-cycle current limit, thermal shutdown,
and short-circuit protection ensure safe operation under
abnormal operating conditions.
● Protection Features
• Cycle-by-Cycle Inductor Peak Current Limit
• Short-Circuit Hiccup Mode, UVLO, and Thermal
Shutdown Protections
• 1ms Default Soft-Start
The MAX77503 is available in a 12-bump, 0.4mm
pitch wafer-level package (WLP).
Applications
●
●
●
●
2-cell/3-cell High Power Density Supplies
Portable Li+/Li-ion Battery Powered Devices
Drones, HD Cameras, and Notebook Computers
Space-Constrained Portable Electronics
● Small Size
• 1.85mm x 1.4mm (0.7mm max. height) WLP
• 12-Bump, 0.4mm Pitch, 3 x 4 Array
Ordering Information appears at end of data sheet.
Simplified Application Circuit
EFFICIENCY vs. LOAD
7.4V SUPPLY, 2520 INDUCTOR CASE SIZE
MAX77503
SUP
BST
4.7μF
100
0.22μF
LX
COUT
OUT
HARDWARE
OR SOFTWARE
ENABLE
VOUT
1.5A MAX
EN
BIASEN
SDA
SCL
AGND
POK
VL
POWER OK
2.2μF
PGND
14V, 1.5A HIGH-EFFICIENCY BUCK CONVERTER
OPTIMIZED FOR 2 OR 3 CELL BATTERY APPLICATIONS
19-100131; Rev 2; 12/18
90
L
80
EFFICIENCY (%)
3V TO 14V
DC INPUT
FEEDBACK
INTERNAL
EXTERNAL
VOUT RANGE
0.8V TO 5V
1.55V TO 99%VSUP
70
V OUT = 5.0V (EXT FB)
60
V OUT = 3.3V (INT FB)
50
V OUT = 1.8V (INT FB)
V OUT = 1.2V (INT FB)
40
V OUT = 0.8V (INT FB)
30
20
10
0
0.00001 0.0001
SKIP MODE
0.001
0.01
0.1
LOAD CURRENT (A)
1
10
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
TABLE OF CONTENTS
General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Simplified Application Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
12 WLP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Bump Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
12 WLP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Bump Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Buck Regulator Control Scheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Mode Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
SKIP Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
FPWM Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Buck Enable Control (EN). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Bias Enable Control (BIASEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
VL Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Soft-Start. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Power-OK (POK) Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Peak Inductor Current Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Active Discharge Resistor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Short-Circuit Protection and Hiccup Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Thermal Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Register Reset Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
I2C Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
MAX77503 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Register Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Buck Enable Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Always-On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Hardware Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Software Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
SUP Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
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Maxim Integrated | 2
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
TABLE OF CONTENTS (CONTINUED)
Output Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Inductor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Setting VOUT and Choosing CFF (MAX77503AEWC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
PCB Layout Guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Typical Application Circuit(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
External Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Internal Feedback, 3.3V Factory Default . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Internal Feedback, 1.8V Factory Default . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Internal Feedback, 1.2V Factory Default . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
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Maxim Integrated | 3
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
LIST OF FIGURES
Figure 1. Buck Control Scheme Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 2. Buck Enable Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 3. External Feedback Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 4. PCB Top-Metal and Component Layout Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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Maxim Integrated | 4
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
LIST OF TABLES
Table 1. Buck Switching Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Table 2. Buck Enable Truth Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 3. VL Enable Truth Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 4. I2C Slave Address Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 5. Inductor Value vs. Output Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 6. Common Feedback Network Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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Maxim Integrated | 5
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Absolute Maximum Ratings
SUP to PGND......................................................... -0.3V to +16V
EN to PGND ............................................... -0.3V to VSUP + 0.3V
BST to LX .............................................................. -0.3V to +2.2V
BST to PGND ...................................................... -0.3V to +17.8V
SDA, SCL to PGND.................................................. -0.3V to +6V
VL to PGND ........................................................... -0.3V to +2.2V
BIASEN, POK to PGND .............. -0.3V to MIN(VSUP+0.3V, +6V)
OUT/FB to PGND ..................................................... -0.3V to +6V
AGND to PGND ..................................................... -0.3V to +0.3V
OUT/FB Short-Circuit Duration ...................................Continuous
LX Continuous Current (Note 1) .................................... 1.6ARMS
Continuous Power Dissipation (Multilayer Board, TA = +70°C)
(derate 13.74mW/°C above +70°C) ............................1099mW
Operating Ambient Temperature Range...............-40°C to +85°C
Junction Temperature ....................................................... +150°C
Soldering Temperature (reflow) ........................................ +260°C
Note 1: LX has internal clamp diodes to PGND and SUP. Applications that forward bias these diodes should not exceed the ICs
package power dissipation limits.
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
12 WLP
Package Code
W121A1+3
Outline Number
21-100250
Land Pattern Number
Refer to Application Note 1891
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
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72.82°C/W
Maxim Integrated | 6
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
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.
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Maxim Integrated | 7
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Electrical Characteristics
(VSUP = VEN = 12V, SKIP mode, VL = 1.8V, configuration registers in reset, TA = TJ = -40ºC to +85ºC, typical values are at TA = TJ =
+25°C, unless otherwise noted. Note 2.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
14
V
3.0
V
STEP-DOWN CONVERTER
SUP Valid Voltage
Range
VSUP
SUP Undervoltage
Lockout
VSUP-UVLO
3
VSUP rising
2.8
SUP UndervoltageLockout Hysteresis
2.9
300
mV
SUP Shutdown Current
ISUP-SHDN
VEN = VBIASEN = 0V (device disabled)
1.2
3
μA
SUP Standby Current
ISUP-STNBY
VEN = 0V, VBIASEN = 1.8V (VL regulator
and internal logic enabled, buck converter
output disabled)
40
60
μA
VOUT = 3.3V,
internal feedback
version
14
30
External feedback
version
40
60
All versions, FPWM
mode
1
1.5
SUP Quiescent Current
VL Regulator Voltage
OUT Voltage Accuracy
FB Voltage Accuracy
FB Input Current
ISUP-Q
VL
VOUT
VFB
μA
VSUP = 3V to 14V
3.3V factory-default
version (VOUT-REG
= 3.3V), FPWM
mode
External feedback
version, FPWM
mode
1.8
VSUP = 12V, IOUT
= 250mA, TJ =
+25°C
3.267
3.3
V
3.333
V
VSUP = 4.5V to
14V, IOUT = 0mA
to 1.5A, TJ = -40°C
to +85°C
3.234
3.3
3.366
VSUP = 12V, ILOAD
= 250mA, TJ =
+25°C
0.792
0.8
0.808
VSUP = 3.0V to
14V, ILOAD = 0mA
to 1.5A, TJ = -40°C
to +85°C
mA
V
0.784
0.8
0.816
VFB = 0.8V, external feedback version
0.02
μA
OUT/FB Load
Regulation
FPWM mode, 0A to 1.5A load, all
versions
0.1
%
OUT/FB Line Regulation
VSUP = 3V to 14V, VOUT = 1.8V, FPWM
mode, IOUT = 0A to 1.5A
0.02
%/VSUP
OUT/FB Soft-Start
Ramp Time
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IFB
ILOAD = 0mA, no
switching
tSS
SFT_STRT[1:0] = 0b00
1
SFT_STRT[1:0] = 0b01
2
SFT_STRT[1:0] = 0b10
4
SFT_STRT[1:0] = 0b11
8
ms
Maxim Integrated | 8
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Electrical Characteristics (continued)
(VSUP = VEN = 12V, SKIP mode, VL = 1.8V, configuration registers in reset, TA = TJ = -40ºC to +85ºC, typical values are at TA = TJ =
+25°C, unless otherwise noted. Note 2.)
PARAMETER
SYMBOL
High-Side DMOS OnResistance
RON-HS
Low-Side DMOS OnResistance
RON-LS
High-Side DMOS Peak
Current Limit
ILX-PEAK
Low-Side DMOS Valley
Current Threshold
ILX-VALLEY
High-Side DMOS
Minimum Current
Threshold
ILX-PK-MIN
Low-Side DMOS ZeroCrossing Threshold
IZX
Low-Side DMOS
Negative Current-Limit
Threshold
INEG
Minimum On-Time
Maximum Duty Cycle
Switching Frequency
CONDITIONS
TYP
MAX
UNITS
VL = 1.8V, ILX = 90mA
90
180
mΩ
VL = 1.8V, ILX = 90mA
55
110
mΩ
ILX-PEAK = 500mA (I_PEAK = 0)
350
500
600
ILX-PEAK = 2000mA (I_PEAK = 1)
1800
2000
2200
Output overloaded
(VOUT < 25% of
target), threshold
below where ontimes are allowed
to start.
ILX-PEAK = 500mA
(I_PEAK = 0)
250
ILX-PEAK =
2000mA (I_PEAK =
1)
1000
Soft-Short Output
Voltage Monitor
Threshold
Output-Overloaded
Retry (Hiccup) Timer
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mA
200
mA
SKIP mode
40
mA
-700
mA
100
ns
99
%
FPWM Mode
tON-MIN
DMAX
FSW
FSW-MIN
mA
Inductor current ramps to at least ILX-PKMIN in SKIP mode
FPWM mode
External feedback
version
0.9
1
1.1
Internal feedback
version, VOUT-REG
≥ 1.55V
0.9
1
1.1
Internal feedback
version, VOUT-REG
≤ 1.5V
Minimum Switching
Frequency
MIN
SKIP mode
VOUT-OVRLD
MHz
0.55
1.43
kHz
0.25 x
VOUT-
V
REG
tRETRY
Switching stopped
due to output
overload (Note 3)
External feedback
version
12
Internal feedback
version, VOUTREG ≥ 1.55V
12
Internal feedback
version, VOUTREG ≤ 1.5V
21.8
ms
Maxim Integrated | 9
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Electrical Characteristics (continued)
(VSUP = VEN = 12V, SKIP mode, VL = 1.8V, configuration registers in reset, TA = TJ = -40ºC to +85ºC, typical values are at TA = TJ =
+25°C, unless otherwise noted. Note 2.)
PARAMETER
SYMBOL
Active Discharge
Resistor
RAD
CONDITIONS
MIN
Between OUT and PGND, buck output
disabled, active discharge resistor
enabled (ADEN = 1), internal feedback
versions only
TYP
MAX
100
UNITS
Ω
POWER-OK OUTPUT (POK)
VPOK-RISE
VOUT rising, expressed as a percentage
of VOUT-REG
90
92
94
VPOK-FALL
VOUT falling, expressed as a percentage
of VOUT-REG
88
90
92
POK Threshold
%
VOUT rising or falling, 1MHz clock
frequency
POK Debounce Timer
tPOK-DB
POK Leakage Current
IPOK
POK = high (high-Z), VPOK = 5V, TA =
+25°C
POK Low Voltage
VPOK
POK = low, sinking 1mA
20
μs
1
μA
0.4
V
ENABLE INPUTS (EN, BIASEN)
EN Logic High
Threshold
VEN_HI
EN Logic Low Threshold
VEN_LO
EN Leakage Current
IEN
BIASEN Logic High
Threshold
VBIASEN_HI
BIASEN Logic Low
Threshold
VBIASEN_LO
1.1
V
0.4
VEN = VSUP = 12V
0.1
V
μA
1.1
V
0.4
V
SERIAL INTERFACE / I/O STAGE
SCL, SDA Input High
Voltage
VIH
SCL, SDA Input Low
Voltage
VIL
SCL, SDA Input
Hysteresis
VHYS
SCL, SDA Input
Leakage Current
II
SDA Output Low
Voltage
VOL
SCL, SDA Pin
Capacitance
Input Filter Suppressed
Spike Maximum Pulse
Width
tSP
1.44
V
0.54
0.3
VSCL = VSDA = 0V or 1.8V
-1
Sinking 20mA
V
V
+1
μA
0.4
V
(Note 4)
10
pF
(Note 4)
50
ns
SERIAL INTERFACE / TIMING
Clock Frequency
www.maximintegrated.com
fSCL
1
MHz
Maxim Integrated | 10
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Electrical Characteristics (continued)
(VSUP = VEN = 12V, SKIP mode, VL = 1.8V, configuration registers in reset, TA = TJ = -40ºC to +85ºC, typical values are at TA = TJ =
+25°C, unless otherwise noted. Note 2.)
PARAMETER
SYMBOL
Bus Free Time between
STOP and START
Condition
tBUF
0.5
μs
Setup Time REPEATED
START Condition
tSU;STA
260
ns
Hold Time REPEATED
START Condition
tHD;STA
260
ns
tLOW
500
ns
SCL High Period
tHIGH
260
ns
Data Setup Time
tSU;DAT
50
ns
Data Hold Time
tHD;DAT
0
μs
Setup Time for STOP
Condition
tSU;STO
260
ns
SCL Low Period
CONDITIONS
MIN
TYP
MAX
UNITS
THERMAL PROTECTION
Thermal Shutdown
Thermal-Shutdown
Hysteresis
TSHDN
Junction temperature rising
+165
°C
+15
°C
Note 2: The MAX77503 is tested under pulsed load conditions such that TA ≈ TJ. Min/Max limits are 100% production tested at TA
= +25°C. Limits over the operating temperature range are guaranteed by design and characterization using statistical quality
control methods. Note that the maximum ambient temperature consistent with this specification is determined by specific
operating conditions, board layout, rated package thermal impedance, and other environmental factors.
Note 3: See the Short-Circuit Protection and Hiccup Mode section.
Note 4: Design guidance only. Not production tested.
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Maxim Integrated | 11
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Typical Operating Characteristics
(VSUP = 12V, VOUT = 1.8V, L = 2.2μH (MURATA 2520 case size), SKIP Mode, ILX-PEAK = 2A, TA = +25ºC, internal feedback
version, unless otherwise noted.)
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Maxim Integrated | 12
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Typical Operating Characteristics (continued)
(VSUP = 12V, VOUT = 1.8V, L = 2.2μH (MURATA 2520 case size), SKIP Mode, ILX-PEAK = 2A, TA = +25ºC, internal feedback
version, unless otherwise noted.)
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Maxim Integrated | 13
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Typical Operating Characteristics (continued)
(VSUP = 12V, VOUT = 1.8V, L = 2.2μH (MURATA 2520 case size), SKIP Mode, ILX-PEAK = 2A, TA = +25ºC, internal feedback
version, unless otherwise noted.)
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Maxim Integrated | 14
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Typical Operating Characteristics (continued)
(VSUP = 12V, VOUT = 1.8V, L = 2.2μH (MURATA 2520 case size), SKIP Mode, ILX-PEAK = 2A, TA = +25ºC, internal feedback
version, unless otherwise noted.)
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Maxim Integrated | 15
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Typical Operating Characteristics (continued)
(VSUP = 12V, VOUT = 1.8V, L = 2.2μH (MURATA 2520 case size), SKIP Mode, ILX-PEAK = 2A, TA = +25ºC, internal feedback
version, unless otherwise noted.)
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Maxim Integrated | 16
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Typical Operating Characteristics (continued)
(VSUP = 12V, VOUT = 1.8V, L = 2.2μH (MURATA 2520 case size), SKIP Mode, ILX-PEAK = 2A, TA = +25ºC, internal feedback
version, unless otherwise noted.)
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Maxim Integrated | 17
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Bump Configuration
12 WLP
TOP VIEW
(BUMP SIDE DOWN)
MAX77503
1
2
3
4
SUP
LX
PGND
SDA
EN
POK
AGND
SCL
VL
BIASEN
OUT/FB
+ BST
A
B
C
12 WLP
(1.85mm x 1.4mm x 0.7mm, 0.4mm PITCH)
Bump Descriptions
PIN
NAME
FUNCTION
A1
BST
High-Side FET Driver Supply. Connect a 0.22μF ceramic capacitor between BST and LX.
A2
SUP
Buck Supply Input. Bypass to PGND with a 4.7μF ceramic capacitor as close to the IC as possible.
A3
LX
A4
PGND
Power Ground. Connect to AGND on the PCB.
B4
AGND
Quiet Ground. Connect to PGND on the PCB.
Switching Node. LX is high-impedance when the converter is disabled.
Internal Feedback Versions: Output Voltage Sense Input. Connect to the positive voltage side of the
output capacitors to regulate the buck output voltage.
C4
OUT/FB
C2
VL
Low-Voltage Internal IC Supply Output. Bypass to AGND with a 2.2μF ceramic capacitor. Do not load
this pin externally.
B3
POK
Open-Drain Power-OK Output. An external pullup resistor (10kΩ to 100kΩ) is required to use this pin.
Leave this pin unconnected if unused.
B2
EN
Enable Input. Drive EN above VEN_HI to enable the buck output. Drive EN to PGND to disable. EN is
compatible with the SUP voltage domain. If using I2C to control the buck, the enable bit (EN_BIT)
interacts with the EN pin. See the Buck Enable Control (EN) section.
C3
BIASEN
BIAS Enable Input. Enables the I2C interface without enabling the buck output. Drive BIASEN above
VBIASEN_HI to enable the I2C interface. Drive to PGND to disable. See the Bias Enable Control
(BIASEN) section for more information.
B1
SDA
I2C Serial Interface Data. Connect to PGND if not used.
C1
SCL
I2C Serial Interface Clock. Connect to PGND if not used.
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External Feedback Version: Feedback Sense Input. Connect a resistor voltage divider between the
converter's output and AGND to set the output voltage. Connect a 5.6pF feed-forward capacitor between
the converter's output and FB. Do not route FB close to sources of EMI or noise.
Maxim Integrated | 18
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Detailed Description
The MAX77503 is a small, high-efficiency 1.5A step-down (buck) DC-DC converter. The step-down converter uses
synchronous rectification and internal current-mode compensation. The buck operates on a supply voltage between 3V
and 14V. Output voltage is configurable through I2C from 0.8V to 5V or external programming resistors between 1.55V
and 99% of VSUP. Factory-default voltage options of 1.2V, 1.8V, and 3.3V are available (see the Ordering Information
table). The buck utilizes an ultra-low quiescent current (IQ) SKIP mode (9μA typ for 1.8VOUT) that maintains very highefficiency at light loads.
Buck Regulator Control Scheme
The step-down converter uses a PWM peak current-mode control scheme with a high-gain architecture. Peak currentmode control provides precise control of the inductor current on a cycle-by-cycle basis and inherent compensation for
supply voltage variation.
On-times (MOSFET Q1 on) are started by a fixed-frequency clock and terminated by a PWM comparator. See Figure
1. When an on-time ends (starting an off-time) current conducts through the low-side MOSFET (Q2 on). Shoot-through
current from SUP to PGND is avoided by introducing a brief period of dead time between switching events when neither
MOSFET is on. Inductor current conducts through Q2's intrinsic body diode during dead time.
The PWM comparator regulates VOUT by controlling duty cycle. The negative input of the PWM comparator is a voltage
proportional to the actual output voltage error. The positive input is the sum of the current-sense signal through MOSFET
Q1 and a slope-compensation ramp. The PWM comparator ends an on-time when the error voltage becomes less than
the slope-compensated current-sense signal. On-times begin again due to a fixed-frequency clock pulse. The controller's
compensation components and current-sense circuits are integrated. This reduces the risk of routing sensitive control
signals on the PCB.
A high-gain architecture is present in the controller design. The feedback uses an integrator to eliminate steady-state
output voltage error while the converter is conducting heavy loads. See the Typical Operating Characteristics section for
information about the converter's typical voltage regulation behavior versus load.
VL
AGND
EN
SCL
SDA
SUP
VL LDO
BIASEN
ILX-PEAK
SLOPE
COMPENSATION
I2C SERIAL
INTERFACE
VL
BST
ILIM
Q1
CLOCK
VOUT-REG
REFERENCE
SOFT-START
RAMP
REGISTERS
& CONTROL
OUT/FB
PWM
S
Q
R
Q
LX
LOGIC
VL
Q2
gm
RCOMP
IZX
CCOMP
POK
ILX-VALLEY
AGND
PGND
Figure 1. Buck Control Scheme Diagram
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Maxim Integrated | 19
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Mode Control
Write the MODE bit to 0 to enable SKIP mode. Write MODE to 1 to enable forced-PWM (FPWM) mode. The default value
of MODE is 0 (SKIP).
SKIP Mode
SKIP mode causes discontinuous inductor current at light loads by forcing the low-side MOSFET (Q2) off if inductor
current falls below IZX (40mA typ) during an off-time. This prevents inductor current from sourcing back to the input (SUP)
and enables high-efficiency by reducing the total number of switching cycles required to regulate the output voltage.
When the load is very light and the output voltage is in regulation, then the converter automatically transitions to
standby mode. In this mode, the LX node is high-impedance and the converter's internal circuit blocks are deactivated
to reduce IQ consumption. Output voltage typically rests 2.5% above the regulation target in standby mode. A lowpower comparator monitors the output voltage during standby. The converter reactivates and starts switching again when
VOUT drops below 102% of regulation target.
FPWM Mode
The low-side MOSFET (Q1) current-limit threshold is INEG (-700mA typ) in FPWM mode, which allows the converter to
switch at constant frequency at light loads. The buck has the best possible load-transient response in this mode at the
cost of higher IQ consumption. Use FPWM for applications that do not require low-IQ and/or when heavy load transients
are expected. Switching frequency is fixed by an internal oscillator in FPWM mode. See Table 1.
Table 1. Buck Switching Frequency
FEEDBACK
External (VOUT set by resistors)
OUTPUT VOLTAGE
SWITCHING FREQUENCY (FSW)
1.55V to 99%VSUP
1MHz
Internal (VOUT set by serial interface)
1.55V to 5V
1MHz
Internal (VOUT set by serial interface)
0.8V to 1.5V
550kHz
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Maxim Integrated | 20
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Buck Enable Control (EN)
Raise the EN pin voltage above VEN_HI (or tie to SUP) to enable the buck output. Lower EN to PGND to disable.
When using I2C to control the device, the EN pin interacts with the enable bit (EN_BIT). The logical relationship between
the EN pin and EN_BIT is by default an OR. Use the EN_LOGIC bit to change this relationship to a logical AND.
See Table 2.
Table 2. Buck Enable Truth Table
EN_LOGIC (BIT)
EN (PIN)
EN_BIT (BIT)
BUCK OUTPUT
0
0
OFF
0
1
ON
1
0
ON
1
1
ON
0
0
OFF
0
1
OFF
1
0
OFF
1
1
ON
0
(logical OR)
1
(logical AND)
The reset state (default state) of EN_BIT and EN_LOGIC is 0. This means that the default relationship between the
enable pin and the enable bit is a logical OR.
Bias Enable Control (BIASEN)
BIASEN is an active-high digital input that enables the device's VL regulator and I2C serial interface. Raise BIASEN
above VBIASEN_HI to activate the serial interface. Lower BIASEN to PGND to deactivate.
Serial I2C reads and writes may happen while SUP is valid and BIASEN is high regardless of whether the buck output is
on or off. This allows the host controller to change the device's configuration registers before enabling the buck output.
When the device is enabled through the EN pin, the BIASEN signal is a don't care. See Table 3.
Table 3. VL Enable Truth Table
EN (PIN)
BIASEN (PIN)
VL AND I2C SERIAL INTERFACE
0
0
OFF
0
1
ON
1
X
ON
VL Regulator
An integrated 1.8V linear regulator (VL) provides power to low-voltage internal circuit blocks and switching FET gate
drivers. VL activates according to Table 3.
VL is powered from SUP for the internal feedback versions of the device when VOUT-REG is < 1.8V. If VOUT-REG is ≥
1.8V, then the VL regulator power input switches from SUP to OUT after the buck soft-start ramp is finished and POK =
1. Switching VL's input to OUT utilizes the buck's high-efficiency to power the linear regulator (as opposed to SUP) and
improves the buck's total power efficiency. VL is permanently powered from SUP for the external feedback version of the
device.
Do not load VL externally for any MAX77503 version. The VL regulator is on whenever EN or BIASEN is high. Connect a
2.2μF ceramic capacitor from VL to ground on the PCB.
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Maxim Integrated | 21
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Soft-Start
The device has an internal soft-start timer (tSS) that controls the ramp time of the output as the converter is starting. Softstart limits inrush current during buck startup. SFT_STRT[1:0] programs tSS to 1ms/2ms/4ms/8ms. The default value of
SFT_STRT[1:0] can be programmed at the factory. The converter soft-starts every time buck is enabled, exits a UVLO
condition, and/or retries from an overcurrent (hiccup) or overtemperature condition.
Power-OK (POK) Output
The device features an active-high, open-drain POK output to monitor the output voltage. POK requires an external pullup
resistor (typically 10kΩ to 100kΩ). POK goes high (high-impedance) after the buck converter output increases above
92% (VPOK-RISE) of the target regulation voltage (VOUT-REG) and the soft-start ramp is done. POK goes low when the
output drops below 90% (VPOK-FALL) of target or when the buck is disabled.
Peak Inductor Current Limit
The buck converter's high-side MOSFET peak current limit (ILX-PEAK) is register programmable. Applications can use
ILX-PEAK programmability to ensure that the converter never exceeds the saturation current rating of the inductor on the
PCB.
Program the I_PEAK bit to 0 to set ILX-PEAK to 500mA. Program I_PEAK to 1 to set ILX-PEAK to 2000mA. The default
value is 1 (2000mA).
Active Discharge Resistor
The device integrates a 100Ω active discharge resistor (RAD) between OUT and PGND that discharges the output
capacitor when the buck is disabled. Write ADEN = 1 through I2C to enable the active discharge resistor function. The
default value of ADEN can be programmed at the factory. The active discharge function is permanently disabled for the
external feedback version of the device.
RAD discharges the output capacitor for 16383 clock periods when ADEN = 1 and the buck is disabled.
● For VOUT-REG ≥ 1.55V, this is approximately 16ms.
● For VOUT-REG ≤ 1.5V, this is approximately 30ms.
The OUT pin returns to a high-impedance state after this time.
Short-Circuit Protection and Hiccup Mode
The device has fault protection designed to protect itself from abnormal conditions. If the output is overloaded, cycle-bycycle current limit prevents inductor current from increasing beyond ILX-PEAK.
The buck stops switching if VOUT falls to less than 25% of programmed VOUT-REG and 15 consecutive on-times are
ended by current limit. After switching stops, the buck waits for tRETRY before attempting to soft-start again (hiccup
mode). While VOUT is less than 25% of target, the converter prevents new on-times if the inductor current has not fallen
below ILX-VALLEY. This prevents inductor current from increasing uncontrollably due to the short-circuited output.
Thermal Shutdown
The device has an internal thermal protection circuit which monitors die temperature. The temperature monitor disables
the buck if the die temperature exceeds TSHDN (165°C typ). The buck soft-starts again after the die temperature cools
by approximately 15°C.
Register Reset Condition
The device's internal configuration registers reset to their default values if VSUP falls below the UVLO falling threshold
(VSUP-UVLO minus UVLO hysteresis, 2.6V typ). Contact the factory to request a version of the device that holds
configuration registers in reset if BIASEN is low.
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Maxim Integrated | 22
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
I2C Serial Interface
All MAX77503 versions feature a revision 3.0 I2C-compatible, 2-wire serial interface consisting of a bidirectional serial
data line (SDA) and a serial clock line (SCL). The MAX77503 is a slave-only device that relies on an external bus master
to generate SCL. SCL clock rates from 0Hz to 3.4MHz are supported. I2C is an open-drain bus, and therefore, SDA and
SCL require pullups.
The device's I2C communication controller implements 7-bit slave addressing. An I2C bus master initiates communication
with the slave by issuing a START condition followed by the slave address. The slave address is factory-programmable
to one of four options (see Table 4). All slave addresses not mentioned in Table 4 are not acknowledged.
The device uses 8-bit registers with 8-bit register addressing. They support standard communication protocols: (1) Writing
to a single register (2) Writing to multiple sequential registers with an automatically incrementing data pointer (3) Reading
from a single register (4) Reading from multiple sequential registers with an automatically incrementing data pointer. For
additional information on the I2C protocols, refer to the MAX77503 I2C Implementer's Guide and/or the I2C specification
that is freely available on the internet.
Table 4. I2C Slave Address Options
7-BIT SLAVE ADDRESS
8-BIT WRITE ADDRESS
8-BIT READ ADDRESS
0x1E
0b 001 1110
0x3C
0b 0011 1100
0x3D
0b 0011 1101
0x24
0b 010 0100
0x48
0b 0100 1000
0x49
0b 0100 1001
0x37
0b 011 0111
0x6E
0b 0110 1110
0x6F
0b 0110 1111
0x77
0b 111 0111
0xEE
0b 1110 1110
0xEF
0b 1110 1111
See the Ordering Information table for the slave address associated with each part number.
Register Map
MAX77503
ADDRESS
NAME
MSB
LSB
Configuration Registers
0x00
CONFIG_A[7:0]
RSVD
0x01
CONFIG_B[7:0]
RSVD
ADEN
SFT_STRT[1:0]
I_PEAK
MODE
EN_LOG
IC
EN_BIT
V_OUTREG[6:0]
Register Details
CONFIG_A (0x00)
7
6
3
2
1
0
Field
BIT
RSVD
ADEN
SFT_STRT[1:0]
I_PEAK
MODE
EN_LOGIC
EN_BIT
Reset
0b0
OTP
OTP
0b1
0b0
0b0
0b0
Write, Read
Write, Read
Write, Read
Write, Read
Write, Read
Write, Read
Write, Read
Access
Type
BITFIELD
RSVD
BITS
7
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5
4
DESCRIPTION
Reserved. Bit is a don't care.
DECODE
N/A
Maxim Integrated | 23
MAX77503
BITFIELD
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
BITS
DESCRIPTION
6
Active discharge resistor enable. This
function is only available in the internal
feedback versions of the device.
This function is permanently disabled in the
external feedback version (bit is a don't care).
0 = disabled
1 = enabled
Soft-start control. Sets the buck converter's
startup ramp time (tSS).
00 = 1ms
01 = 2ms
10 = 4ms
11 = 8ms
ADEN
SFT_STRT
5:4
DECODE
I_PEAK
3
High-side DMOS peak current-limit threshold
control. Sets peak LX current limit (ILX-PEAK).
0 = 500mA
1 = 2000mA
MODE
2
Buck converter mode control.
0 = SKIP mode
1 = FPWM mode
EN_LOGIC
1
Enable logic control bit. Determines the
logical relationship between EN_BIT (enable
bit) and EN (enable pin).
0 = logical OR relationship
1 = logical AND relationship
EN_BIT
0
Buck enable bit.
0 = disabled
1 = enabled
CONFIG_B (0x01)
BIT
7
6
5
4
3
2
1
Field
RSVD
V_OUTREG[6:0]
Reset
0b0
0x08 / 0x14 / 0x32 (See the Ordering Information table)
Write, Read
Write, Read
Access
Type
BITFIELD
RSVD
BITS
7
DESCRIPTION
Reserved. Bit is a don't care.
Output Voltage Control (internal feedback
versions only). Sets VOUT-REG.
Programmable in 50mV per LSB from 0x00
(0.8V) to 0x54 (5V).
V_OUTREG
6:0
The default value of this register is preset for
internal feedback versions of the device. See
the Ordering Information table. Overwriting
the default value sets a new target output
voltage.
This register is a don't care for the external
feedback version of the device.
Avoid changing this bitfield while the
converter is both enabled and loaded.
Increasing the VOUT target while the buck is
supplying load may cause the converter to
enter hiccup mode.
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0
DECODE
N/A
0x00 = 0.80V
0x01 = 0.85V
0x02 = 0.90V
...
0x08 = 1.20V
....
0x14 = 1.80V
...
0x32 = 3.30V
...
0x53 = 4.95V
0x54-0x7F = 5.0V
Maxim Integrated | 24
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
Applications Information
Buck Enable Options
The MAX77503 offers a high degree of control flexibility. See Figure 2 for suggested methods of controlling the buck
converter.
ALWAYS-ON
CONFIGURATION
BUCK
INPUT
CONNECT
EN TO SUP
MAX77503
SUP
HARDWARE CONTROL
CONFIGURATION
BUCK
INPUT
EN
MAX77503
SUP
EN
DRIVE EN PIN
SOFTWARE CONTROL
CONFIGURATION
BUCK
INPUT
GROUND EN FOR
FULL SOFTWARE
CONTROL
SET BIASEN HIGH
& SEND SOFTWARE
COMMANDS
MAX77503
SUP
EN
BIASEN
SDA
SCL
Figure 2. Buck Enable Options
Always-On
Strap the EN pin to SUP to configure the device in an always-on configuration. See Figure 2 (left). The buck converter
activates whenever VSUP is valid and TJ < TSHDN.
Hardware Control
Drive the EN pin externally to control the buck. See Figure 2 (center). The buck converter activates whenever VEN >
VEN_HI (1.1V min), TJ < TSHDN, and VSUP is valid.
The default relationship between the EN pin and the EN_BIT is a logic OR. See Table 2 for more details.
Software Control
Use the I2C serial interface to control the buck by connecting SDA and SCL to a serial host. See Figure 2 (right).
Assert BIASEN logic high to first activate the I2C serial interface. The serial host can now do the following:
●
●
●
●
●
●
Set the target output voltage, VOUT-REG (internal feedback versions only).
Set the desired soft-start time, tSS.
Set the peak inductor current limit, ILX-PEAK.
Enable the buck output using EN_BIT.
Change the converter mode (SKIP/FPWM) dynamically.
Control the active discharge resistor (internal feedback versions only).
See the I2C Serial Interface and Register Map sections for more information. Configuration registers reset if VSUP falls
below VSUP-UVLO (2.6V typ). Contact the factory to request a version of the device that holds configuration registers in
reset if BIASEN is low.
SUP Capacitor Selection
Choose the input capacitor (CSUP) to be a 4.7μF nominal capacitor that maintains 1μF effective capacitance at its
working voltage. Larger values improve the decoupling of the buck converter, but increase inrush current from the voltage
supply when connected. CSUP reduces the current peaks drawn from the input power source during buck operation and
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Maxim Integrated | 25
MAX77503
14V Input, 1.5A High-Efficiency
Buck Converter with 9μA IQ
reduces switching noise in the system. The ESR/ESL of CSUP and its series PCB trace should be very low (i.e.,
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