MAX20021ATIB/V+T - Maxim Integrated

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

General Description

The MAX20021/MAX20022 power-management ICs

(PMICs) integrate four low-voltage, high-efficiency, step-

down DC-DC converters. Each of the four outputs is

factory or resistor programmable between 1.0V to 4.0V

and can deliver up to 1.0A of current. The PMICs operate

from 3.0V to 5.5V, making them ideal for automotive point-

of-load and post-regulation applications.

The PMICs feature fixed-frequency PWM-mode operation

with a switching frequency of 2.2MHz or 3.2MHz. High-

frequency operation allows for an all-ceramic capacitor

design and small-size 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. Internal current sensing and loop compensation

reduce board space and system cost.

The PMICs offer a spread-spectrum option to reduce

radiated emissions. Two of the four buck converters oper-

ate 180º out-of-phase with the internal clock. This feature

reduces the necessary input capacitance and improves

EMI as well. All four buck converters operate in constant-

PWM mode outside the AM band. The PMICs offer a

SYNC input to synchronize to an external clock.

The PMICs provide individual enable inputs and power-

good/reset outputs, as well as factory-programmable

RESET times.

The PMICs offer several important protection features

including: input overvoltage protection, input undervoltage

monitoring, input undervoltage lockout, cycle-by-cycle

current limiting, and overtemperature shutdown. The

input undervoltage monitor indicates a brownout condition

by driving PG_ low when the input falls below the UVM

threshold.

The MAX20021/MAX20022 PMICs are available in a

28-pin TQFN package with an exposed pad and are

specified for operation over the -40ºC to +125ºC automo-

tive temperature range.

Applications

● Automotive

● Industrial

Benets and Features

● Quad Step-Down DC-DC Converters with Integrated

FETs

● Operate from 3.0V to 5.5V Supply Voltage

● 1.0V to 4.0V Fixed or Adjustable Output Voltage

● 2.2MHz (MAX20022) or 3.2MHz (MAX20021)

Switching Frequency

● Four Channels Capable of Delivering Up to 1A Each

● Designed to Improve Automotive EMI Performance

• Forced-PWM Operation

• Two Channels 180º Out-of-Phase

• SYNC Input

• Spread-Spectrum Option

● Soft-Start and Supply Sequencing Reduces Inrush

Current

● Individual Enable Inputs and Power-Good Outputs to

Simplify Sequencing

● OV/UV Input-Voltage Monitoring

● Overtemperature and Short-Circuit Protection

● 28-Pin (5mm x 5mm x 0.8mm) TQFN-EP Package

● -40ºC to +125ºC Operating Temperature Range

19-6628; Rev 3; 8/14

Ordering Information/Selector Guide appear at end of data

sheet.

For related parts and recommended products to use with this part, refer

to www.maximintegrated.com/MAX20021.related.

Simplied Block Diagram

EVALUATION KIT AVAILABLE

PGND_

LX_

SYNC

OUTS_

CONTROL

VOUT1

10µF

1.5µH

VOUT

MAX20021

2.2µF

1µF

EN_

PG_

GND

SEL

STEP-DOWN

PWM OUT_

1.0V TO 4.0V

UP TO

0.5A OR 1A

SS OSC

4 CHANNELS PV_

10kΩ

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Electrical Characteristics

(VA = VPV1 = VPV2 = VPV3 = VPV4 = 5.0V; TA = TJ = -40ºC to +125ºC, unless otherwise noted. Typical values are at TA = +25ºC under

normal conditions, unless otherwise noted.) (Note 2)

Note 1: 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.

PV_ to PGND_ .....................................................-0.3V to +6.0V

VA to GND ............................................................ -0.3V to +6.0V

OUTS_, EN_, PG_, SYNC, SEL to GND ......-0.3V to VA + 0.3V

PV_ to PV_ ........................................................... -0.3V to +0.3V

PGND_ to GND ....................................................-0.3V to +0.3V

LX_ to PGND...............................................-1.0V to PV_ + 0.3V

LX_ Continuous RMS Current ..............................................2.0A

Output Short-Circuit Duration .................................... Continuous

Continuous Power Dissipation (TA = +70ºC)

TQFN (derate 28.6mW/ºC above +70ºC) ..................2285mW

ESDHB .................................................................................±2kV

ESDMM ..............................................................................±200V

Operating Temperature Range .......................... -40ºC to +125ºC

Junction Temperature ...................................................... +150ºC

Storage Temperature Range .............................-65ºC to +150ºC

Lead Temperature (soldering, 10s) ................................. +300ºC

Soldering Temperature (reflow) ....................................... +260ºC

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 Thermal Characteristics (Note 1)

TQFN

Junction-to-AmbientThermalResistance(θJA) ..............35°C/W Junction-to-CaseThermalResistance(θJC) .....................3°C/W

Absolute Maximum Ratings

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNIT

GENERAL

Supply Voltage Range VPV_ Fully operational 3.0 5.5 V

Supply Current IPV0

No load, no switching,

VEN1 = VEN2 = VEN3 = VEN4 = VPV_

2.5 3.8 5 mA

Shut-Off Current IVPSD

VEN1 = VEN2 = VEN3 =

VEN4 = VGND

TA = +25°C 0.1 2 µA

TA = +125°C 2

Overvoltage Threshold Rising 5.6 5.8 6 V

Hysteresis 0.1

Undervoltage Monitor Threshold UVM option enabled VPV_ falling 4.15 4.3 4.45 V

VPV_ hysteresis 0.1

UVLO Threshold VPV_ falling 2.68 V

VPV_ rising 3.0

PWM Switching Frequency fSW

Switching frequency = 2.2MHz

(see the Selector Guide)2.0 2.2 2.4

MHz

Switching frequency = 3.2MHz

(see the Selector Guide)3.0 3.2 3.4

Spread Spectrum Df/f Spread-spectrum option = enabled

(see the Selector Guide) +3 %

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Electrical Characteristics (continued)

(VA = VPV1 = VPV2 = VPV3 = VPV4 = 5.0V; TA = TJ = -40ºC to +125ºC, unless otherwise noted. Typical values are at TA = +25ºC under

normal conditions, unless otherwise noted.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNIT

SYNC Input Frequency Range fSYNC

PWM switching frequency = 2.2MHz

(see the Selector Guide)1.7 2.5

MHz

PWM switching frequency = 3.2MHz

(see the Selector Guide)2.8 3.5

OUT1, OUT2, OUT3, OUT4—SYNCHRONOUS STEP-DOWN DC-DC CONVERTERS

Fixed DC Output Accuracy ILOAD = 0mA +1.5 %

ILOAD = 0mA to IMAX -3 +3

FB DC Set-Point Accuracy VSFB_ MAX20022 ILOAD = 0mA 1015 mV

ILOAD = 0mA to IMAX 970 1030

Load Regulation ILOAD = IMAX -1.5 -2.5 %

Line Regulation ILOAD = IMAX/2, VPV_ = 4.5V to 5.5V +0.3 %

pMOS On-Resistance VPV_ = 5.0V, ILX_ = 0.2A 125 250 mΩ

nMOS On-Resistance VPV_ = 5.0V, ILX_ = 0.2A 100 200 mΩ

pMOS Current-Limit Threshold ILIM

1.0A channel output

(see the Selector Guide)1.4 1.65 2

0.5A channel output

(see the Selector Guide)0.8 1.1 1.5

Soft-Start Ramp Time 3272 Cycles

OUTS Leakage Current IB_OUTS_ Externally adjustable output 20 nA

LX Leakage Current VPV_ = 5.0V, LX_ = VPGND_ or VPV_ 0.1 µA

Minimum On-Time 45 66 ns

LX Rise/Fall Time 4 ns

Duty Cycle Range 100 %

OUTS_ Discharge Resistance VEN_ = VGND 35 Ω

OUT1, OUT2 Phasing (Note 3) 0 Degrees

OUT3, OUT4 Phasing (Note 3) 180 Degrees

THERMAL OVERLOAD

Thermal-Shutdown Temperature TJ rising (Note 4) +185 ºC

Hysteresis (Note 4) 15 ºC

OUTPUT POWER-GOOD INDICATORS (PG_)

Output Overvoltage Threshold VOUT rising (percentage of nominal output) 106 110 114 %

Output Undervoltage Threshold VOUT falling (percentage of nominal output) 92.5 94 96 %

VOUT rising (percentage of nominal output) 93.5 95 97

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Note 2: All units are 100% production tested at +25ºC. All temperature limits are guaranteed by design.

Note 3: Phase measurement is in relation to the rising edge of VLX_.

Note 4: Guaranteed by design. Not production tested.

Electrical Characteristics (continued)

(VA = VPV1 = VPV2 = VPV3 = VPV4 = 5.0V; TA = TJ = -40ºC to +125ºC, unless otherwise noted. Typical values are at TA = +25ºC under

normal conditions, unless otherwise noted.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNIT

UV/OV Propagation Delay 15 µs

PG_ Output High Leakage

Current 0.1 µA

PG_ Output Low Level VPV_= 3.0V, sinking 3mA 0.22 V

ENABLE INPUTS (EN_)

Input High Level VPV_ = 5.0V, VEN_ rising 0.7 1.0 1.3 V

Hysteresis VPV_ = 5.0V, VEN_ falling 50 mV

Pulldown Resistance 100 kΩ

DIGITAL INTERFACE (SYNC, SEL)

Input Voltage High VINH 1.5 V

Input Voltage Low VINL 0.5 V

Input Voltage Hysteresis 70 mV

Pulldown Resistance 100 kΩ

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Typical Operating Characteristics

(VA = VPV1 = VPV2 = VPV3 = VPV4 = 5.0V; TA = +25ºC, unless otherwise noted.)

BUCK EFFICIENCY (3.2MHz)

vs. LOAD CURRENT

MAX20021 toc01

LOAD CURRENT (A)

EFFICIENCY (%)

0.10000.01000.00100.0001 1.0000

100

VOUT2 = 1.2V

VOUT4 = 1.8V

VOUT1 = 3.3V

VOUT3 = 2.65V

fSW = 3.2MHz, VPV_ = 5V

LX LEAKAGE CURRENT

vs. TEMPERATURE

MAX20021 toc04

TEMPERATURE (ºC)

LX LEAKAGE CURRENT (nA)

80 100 12040 60-40 -20 200

100

200

300

400

500

600

700

800

-100

-60 140

LX_ TO PV_

LX_ TO PGND_

BUCK EFFICIENCY (2.2MHz)

vs. LOAD CURRENT

MAX20021 toc02

LOAD CURRENT (A)

EFFICIENCY (%)

0.10000.01000.00100.0001 1.0000

100

fSW = 2.2MHz, VPV_ = 5V

VOUT2 = 1.2V

VOUT4 = 1.8V

VOUT1 = 3.3V

VOUT3 = 2.65V

LOAD REGULATION (BUCK 1)

MAX20021 toc05

IOUT1 (A)

VOUT1 (V)

0.80.7 0.90.60.50.20.1 0.40.3

3.22

3.24

3.26

3.28

3.32

3.30

3.34

3.36

3.20

0 1.0

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX20021 toc03

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

5.24.74.23.73.2

2.7 5.7

TA = -40ºC

TA = +25ºC

TA = +125ºC

VPV_ = VA = VEN_

LINE REGULATION (BUCK 2)

MAX20021 toc06

VPV2 (V)

VOUT2 (% NOMINAL)

5.24.74.23.73.2

99.8

100.0

100.2

100.4

100.6

100.8

101.0

99.6

2.7 5.7

TA = +125ºC

TA = +25ºC

TA = -40ºC

STARTUP SEQUENCE

MAX20021 toc07

2ms/div

VOUT1

VOUT2

VOUT3

VOUT4

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Typical Operating Characteristics (continued)

(VA = VPV1 = VPV2 = VPV3 = VPV4 = 5.0V; TA = +25ºC, unless otherwise noted.)

SHORT-CIRCUIT BEHAVIOR

MAX20021 toc08

400ns/div

VOUT3

2V/div

VLX3

2V/div

IOUT3

1A/div

LINE TRANSIENT, (VOUT1 = 3.3V)

MAX20021 toc10

10ms/div

VPV1

1V/div

VOUT1

50mV/div

VPV1 = 3.8VVPV1 = 5.2VVPV1 = 3.8V

LOAD TRANSIENT, (VOUT1 = 3.3V)

MAX20021 toc09

10µs/div

IOUT1

500mA/div

VOUT1

100mV/div

P-CHANNEL SWITCH RESISTANCE

vs. SUPPLY VOLTAGE

MAX20021 toc13

VPV_ (V)

P-CHANNEL SWITCH RESISTANCE (Ω)

5.75.24.74.23.73.2

0.05

0.10

0.15

0.20

0.25

0.30

0.35

2.7

TA = +125ºC

TA = -40ºC

TA = +25ºC

SWITCHING FREQUENCY

vs. TEMPERATURE

MAX20021 toc11

fSW (% NOMINAL)

100

101

102

103

80 100 12040

TEMPERATURE (°C)

60-40 -20 200-60 140

DROPOUT VOLTAGE

vs. LOAD CURRENT (BUCK 1)

MAX20021 toc12

VPV1 - VOUT1 (mV)

100

150

200

250

300

350

IOUT1 (A)

0.80.7 0.9

0.60.50.20.1 0.40.30 1.0

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Typical Operating Characteristics (continued)

(VA = VPV1 = VPV2 = VPV3 = VPV4 = 5.0V; TA = +25ºC, unless otherwise noted.)

PSRR vs. FREQUENCY

MAX20021 toc16

FREQUENCY (kHz)

PSRR (dB)

100.00010.0001.0000.1000.010

-60

-50

-40

-30

-20

-10

-70

0.001 1000.000

NO LOAD

150mA LOAD

SMALL-SIGNAL GAIN

vs. FREQUENCY

MAX20021 toc14

FREQUENCY (Hz)

MAGNITUDE (dB)

1E+51E+41E+3

-45

1E+2 1E+6

OUTPUT VOLTAGE-NOISE DENSITY

vs. FREQUENCY

MAX20021 toc17

RF FREQUENCY (MHz)

OUTPUT VOLTAGE-NOISE DENSITY (nV/√Hz)

3000 35001500 2000 25001000500

100

1000

10,000

0 4000

VPV_ = 5V

VOUT_ = 1.2V

IOUT_ = 0mA

PHASE MARGIN vs. FREQUENCY

MAX20021 toc15

FREQUENCY (Hz)

PHASE MARGIN (°)

1E+51E+41E+3

-50

100

150

200

-100

1E+2 1E+6

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Pin Description

Pin Conguration

PIN NAME FUNCTION

1 EN1 Active-High Digital Enable Input for Buck 1. Driving EN1 high enables Buck 1.

2 PV1 Buck 1 Voltage Input. Connect a 2.2µF or larger ceramic capacitor from PV1 to PGND1 as close

as possible to the device.

3 LX1 Buck 1 Switching Node. LX1 is high impedance when the device is off.

4 PGND1 Power Ground for Buck 1

5 PGND2 Power Ground for Buck 2

6 LX2 Buck 2 Switching Node. LX2 is high impedance when the device is off.

7 PV2 Buck 2 Voltage Input. Connect a 2.2µF or larger ceramic capacitor from PV2 to PGND2 as close

as possible to the device.

8 OUTS2 Buck 2 Voltage Sense Input

9 EN2 Active-High Digital Enable Input for Buck 2. Driving EN2 high enables Buck 2.

10 PG2 Open-Drain, Active-High, Power-Good Output for Buck 2. To obtain a logic signal, pull up PG2

with an external resistor connected to a positive voltage equal to or lower than VA.

11 SEL Buck 3 Output-Voltage Select Input. Connect SEL to PGND_ for a 1.8V output. Connect SEL to

PV_ for a 2.65V output. Do not toggle during normal operation.

12 PG3 Open-Drain, Active-High, Power-Good Output for Buck 3. To obtain a logic signal, pull up PG3

with an external resistor connected to a positive voltage equal to or lower than VA.

13 EN3 Active-High Digital Enable Input for Buck 3. Driving EN3 high enables Buck 3.

14 OUTS3 Buck 3 Voltage Sense Input

PV1

PGND1

PGND2

LX2

PV2

EN1

PV4

PGND4

PGND3

EN4

LX3

PV3

EP = GND

SYNC

4567

2021 19 17 16 15

PG1

PG3

SEL

PG2

EN2

MAX20021

LX1LX4

28 8

OUTS1 OUTS2

GND

23 13 EN3

PG4

22 14 OUTS3

OUTS4

TQFN

TOP VIEW

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Pin Description (continued)

PIN NAME FUNCTION

15 PV3 Buck 3 Voltage Input. Connect a 2.2µF or larger ceramic capacitor from PV3 to PGND3 as close

as possible to the device.

16 LX3 Buck 3 Switching Node. LX3 is high impedance when the device is off.

17 PGND3 Power Ground for Buck 3

18 PGND4 Power Ground for Buck 4

19 LX4 Buck 4 Switching Node. LX4 is high impedance when the device is off.

20 PV4 Buck 4 Voltage Input. Connect a 2.2µF or larger ceramic capacitor from PV4 to PGND4 as close

as possible to the device.

21 EN4 Active-High Digital Enable Input for Buck 4. Driving EN4 high enables Buck 4.

22 OUTS4 Buck 4 Voltage Sense Input

23 PG4 Open-Drain, Active-High, Power-Good Output for Buck 4. To obtain a logic signal, pull up PG4

with an external resistor connected to a positive voltage equal to or lower than VA.

24 GND Analog Ground

25 SYNC SYNC Input. Supply an external clock to control the switching frequency. Connect SYNC to

PGND_ to use the default switching frequency.

26 VA

Analog Voltage Supply. Connect a 1µF or larger ceramic capacitor from VA to GND as close as

possible to the device. Connect to the same supply as PV_ inputs.

27 PG1 Open-Drain, Active-High, Power-Good Output for Buck 1. To obtain a logic signal, pull up PG1

with an external resistor connected to a positive voltage equal to or lower than VA.

28 OUTS1 Buck 1 Voltage Sense Input

— EP

Exposed Pad. Connect the exposed pad to ground. Connecting the exposed pad to ground does

not remove the requirement for proper ground connections to PGND1–PGND4 and GND. The

exposed pad is attached with epoxy to the substrate of the die, making it an excellent path to

remove heat from the IC.

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Figure 1. Internal Block Diagram

CONTROL

LOGIC

PEAK

CURRENT

COMP PV1

PGND1

CURRENT-SENSE

AMP PV1—PV4

LX1—LX4

PGND1

—PGND4

PG1

PG2

PG3

PG4

GND

OUTS1—

OUTS4

SYNC

EN1

EN2

EN3

EN4

SEL

CLK

CLK180

PWM

COMP

CLK180 CLK

SOFT-START

GENERATOR

FEEDBACK

SELECT

OSC

MAX20021

P1-OK

VREF

SEL

P-OK[1:4]

VALLEY

CURRENT

LIM COMP

RAMP

GENERATOR

VREF

∑

PV1

PGND1

VREF UVLO

VOLTAGE

REFERENCE

TRIMBITS

OTP

MAIN

CONTROL

LOGIC

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Detailed Description

The MAX20021/MAX20022 PMICs offer four, high-

efficiency, synchronous step-down converters that oper-

ate with a 3.0V to 5.5V input voltage range and provide

a 1.0V to 4.0V output voltage range. The PMICs deliver

up to 1.0A of load current per output. The PMICs achieve

±3% output error over load, line, and temperature ranges.

The PMICs feature fixed-frequency PWM-mode operation

with a 2.2MHz or 3.2MHz switching frequency. An optional

spread-spectrum frequency modulation minimizes radiated

electromagnetic emissions due to the switching frequency,

while a factory-programmable synchronization input (SYNC)

allows the device to synchronize to an external clock.

Integrated low RDSON switches help minimize efficien-

cy losses at heavy loads and reduce critical/parasitic

inductance, making the layout a much simpler task with

respect to discrete solutions.

The PMICs are offered in factory-preset output voltages to

allow customers to achieve ±3% output-voltage accuracy,

without using expensive 0.1% resistors. In addition, adjust-

able output-voltage versions can be set to any desired

values between 1.0V and 4.0V using an external resistive

divider. See the Selector Guide for available options.

Additionally, each converter features soft-start, PG_

output, overcurrent, and overtemperature protections

(see Figure 1).

Control Scheme

The PMICs use peak current-mode control. The devices

feature internal slope compensation and internal loop

compensation, both of which reduce board space and

allow a very compact solution.

Hybrid Load-Line Architecture

The PMICs feature hybrid load-line architecture to reduce

the output capacitance needed, potentially saving system

cost and size. This results in a measurable load transient

response.

Input Overvoltage Monitoring (OV)

The PMICs feature an input overvoltage-monitoring circuit

on the input supply. When the input exceeds 5.8V (typ)

all power-good indicators (PG_) go low. When the input

supply returns to within the operating range of 5.7V (typ)

or less during the timeout period, the power-good indica-

tors go high.

Input Undervoltage Monitoring (UVM)

The MAX20021 features an input undervoltage monitor-

ing circuit on the input supply. When the input drops below

4.3V (typ), all power-good indicators (PG_) go low to indi-

cate a potential brownout condition. The device remains

operational down to the UVLO threshold. When the input

voltage exceeds the UV threshold above 4.4V (typ),

PG_ remains low for the factory-trimmed “active timeout

period.” UVM is a factory-selectable option.

Input Undervoltage Lockout (UVLO)

The PMICs feature an undervoltage lockout on the PV_

inputs set at 2.77V (typ) falling. This prevents loss of con-

trol of the device by shutting down all outputs. This circuit

is only active when at least one buck converter is enabled.

Power-Good Outputs (PG_)

The PMICs feature an open-drain power-good output for

each of the four buck regulators. PG_ asserts low when

the output voltage drops 6% below the regulated voltage

or 10% above the regulated voltage for approximately

15µs. PG_ remains asserted for a fixed 20,480 switching

cycles after the output returns to its regulated voltage.

PG_ asserts low during soft-start and in shutdown. PG_

becomes high impedance when Buck_ is in regulation.

ConnectPG_toalogicsupplywitha10kΩresistor.

Soft-Start

The PMICs include a 3272 switching cycle fixed-duration

soft-start time. The soft-start time limits startup inrush

current by forcing the output voltage to ramp up towards

its regulation point. During soft-start, the converters oper-

ate in skip mode to prevent the outputs from discharging.

When the PMICs exit UVLO or thermal shutdown, there

is a fixed blanking time for EN2–EN4 to prevent all four

outputs from going through soft-start at the same time.

After 24,576 switching cycles with UVLO high and at least

one buck converter enabled, there is no blanking time

between EN2–EN4 high and the start of soft-start.

Figure 2. Load Transient Response

+5.0%

+1.5%

-1.0%

-3.5%

1.0A

4µs

1µ

µs

4µs

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

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Output 3 Voltage Select (SEL)

The MAX20021 offers a SEL input to allow selection of the

OUT3 voltage. For fixed output versions, connect SEL to

PGND_ for a 1.8V output or to PV_ for a 2.65V output.

There is no soft transition between the two output-voltage

settings, so SEL should not be toggled during normal

operation. For the MAX20022, connect SEL to PGND_ or

leave unconnected.

Spread-Spectrum Option

The PMICs feature a linear spread-spectrum (SS) opera-

tion, which varies the internal operating frequency between

fSW and (fSW + 3%). The internal oscillator is frequency

modulated at a rate of 1.5kHz with a frequency deviation

of 3% (see Figure 4). This function does not apply to an

oscillation frequency applied externally through the SYNC

pin. Spread spectrum is a factory-selectable option. See

the Selector Guide for available options.

Synchronization (SYNC)

The PMICs feature a SYNC input to allow the internal

oscillator to synchronize with an external clock. SYNC

accepts signal frequencies in the range of 1.7MHz <

fSYNC < 2.5MHz (2.2MHz option), or 2.7MHz < fSYNC <

3.5MHz (3.2MHz option). Connect to PGND_ if the SYNC

feature is not used.

Current Limit /Short-Circuit Protection

The PMICs offer a current-limit feature that protects the

devices against short-circuit and overload conditions on

each output. In the event of a short-circuit or overload

condition at an output, the high-side MOSFET remains on

until the inductor current reaches the high-side MOSFET’s

current-limit threshold. The converter then turns on the

low-side MOSFET and the inductor current ramps down.

The converter allows the high-side MOSFET to turn on

only when the inductor current ramps down to the low-

side MOSFET’s current threshold. This cycle repeats until

the short or overload condition is removed.

Overtemperature Protection

Thermal-overload protection limits the total power dissipa-

tion in the PMICs. When the junction temperature exceeds

185ºC (typ), an internal thermal sensor shuts down the

step-down converters, allowing the IC to cool. The thermal

sensor turns on the IC again after the junction temperature

cools by 15ºC. The IC goes through a standard power-up

sequence as defined in the Soft-Start section.

Applications Information

Adjustable Output-Voltage Option

The MAX20022 features adjustable output voltages (see

the

Selector Guide

for more details), which allows the cus-

tomer to set the outputs to any voltage between 1.0V and

VPV_ - 0.5V (up to 4.0V). Connect a resistive divider from

output (VOUT_) to OUTS_ to GND to set the output volt-

age (see Figure 5). Select R2 (OUTS_ to the GND resis-

tor)lessthanorequalto100kΩ.CalculateR1(VOUT_ to

the OUTS_ resistor) with the following equation:

OUT_

OUTS_

R1 R2 1









= −









where

VOUTS_

= 1000mV (see the Electrical

Characteristics table). The output voltage is nominal at

50% load current.

Figure 3. Power-Up Soft-Start Delays

Figure 4. Effect of Spread-Spectrum on Internal Oscillator

UVLO

EN1—EN4

OUT1

OUT2

OUT3

OUT4

8192 CYCLES

16,384 CYCLES

24,576 CYCLES

3272 CYCLES

3272 CYCLES 3272 CYCLES

fSW + 3%

fSW

tt + 667µs

TIME

t + 1.334ms

INTERNAL

OSCILLATOR

FREQUENCY

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

www.maximintegrated.com Maxim Integrated

│

The external feedback resistive divider must be frequency

compensated for proper operation. Place a capacitor

across R1 in the resistive divider network. Use the follow-

ing equation to determine the value of the capacitor:

R2 R2

I f 1, C1 C

R1 R1

else C1 C, where C 15pF







= =

Connect OUTS_ to VOUT_ for a fixed 1.0V output voltage.

Inductor Selection

The PMICs are optimized for use with a 1.5µH inductor

for 2.2MHz and 3.2MHz operation. Chip inductors can be

used for additional board-space savings.

Input Capacitor

The PMICs are designed to operate with a single 2.2µF

ceramic bypass capacitor on each PV_ input. Phase

interleaving of the four buck converters contributes to

a lower required input capacitance by canceling input

ripple currents. Place the bypass capacitors as close as

possible to their corresponding PV_ input to ensure the

best EMI and jitter performance.

Output Capacitor

All outputs of the PMICs are optimized for use with a 10FF

X7R ceramic capacitor. Additional output capacitance can

be used if better voltage ripple or load transient response

is required. Due to the soft-start sequence, the device is

unable to drive arbitrarily large output capacitors.

Thermal Considerations

How much power the package can dissipate strongly

depends on the mounting method of the IC to the PCB

and the copper area for cooling. Using the JEDEC test

standard, the maximum power dissipation allowed is

2285mW in the TQFN package. More power dissipation

can be handled by the package if great attention is given

during PCB layout. For example, using the top and bottom

copper as a heatsink and connecting the thermal vias to

one of the middle layers (GND) transfers the heat from the

package into the board more efficiently, resulting in lower

junction temperature at high power dissipation in some

PMIC applications. Furthermore, the solder mask around

the IC area on both top and bottom layers can be removed

to radiate the heat directly into the air. The maximum

allowable power dissipation in the IC is as follows:

( )

J(MAX) A

MAX JC CA

P−

=θ +θ

where TJ(MAX) is the maximum junction temperature

(+150ºC), TA is the ambient air temperature, BJC (3ºC/W

for the 28-pin TQFN) is the thermal resistance from the

junctiontothecase,andθCA is the thermal resistance from

the case to the surrounding air through the PCB, copper

traces,andthepackagematerials.θCA is directly related

to system-level variables and can be modified to increase

the maximum power dissipation.

The TQFN package has an exposed thermal pad on its

underside. This pad provides a low thermal-resistance path

for heat transfer into the PCB. This low thermally resistive

path carries a majority of the heat away from the IC. The

PCB is effectively a heatsink for the IC. The exposed pad

should be connected to a large ground plane for proper

thermal and electrical performance. The minimum size of

the ground plane is dependent upon many system vari-

ables. To create an efficient path, the exposed pad should

be soldered to a thermal landing, which is connected to

the ground plane by thermal vias. The thermal landing

should be at least as large as the exposed pad and can be

made larger depending on the amount of free space from

the exposed pad to the other pin landings. A sample lay-

out is available on the MAX20022 evaluation kit to speed

designs.

PCB Layout Guidelines

Careful PCB layout is critical to achieve low switching

losses and clean, stable operation. Use a multilayer board

whenever possible for better noise immunity and power

dissipation. Follow these guidelines for good PCB layout:

1) Use a large contiguous copper plane under the PMIC

packages. Ensure that all heat-dissipating components

have adequate cooling.

2) Keep the high-current paths short, especially at the

ground terminals. This practice is essential for stable,

jitter–free operation. The high current path comprising

of input capacitor, inductor, and the output capacitor

should be as short as possible.

Figure 5. Adjustable Output-Voltage Configuration

MAX20022

VOUT_

R1 C1

OUTS_

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

www.maximintegrated.com Maxim Integrated

│

3) Keep the power traces and load connections short. This

practice is essential for high efficiency. Use thick copper

PCBs (2oz vs. 1oz) to enhance full-load efficiency.

4) Use a single ground plane to reduce the chance of

ground potential differences. With a single ground

plane, enough isolation between analog return signals

and high-power signals must be maintained.

Typical Operating Circuit

PGND1

LX1

OUTS1

CONTROL

10µF

1.5µH

3.3V

MAX20021

2.2µF

STEP-DOWN

PWM OUT1

1.0V TO 4.0V

1.0A

SYNC

SS OSC

PV1

EN4

SEL

EN3

EN2

EN1

PG1

PG2

PG3

PG4

VOUT1

10kΩ

VOUT1

10kΩ

1µF

GND

PGND2

LX2

OUTS2

10µF

1.5µH

1.25V

2.2µF

STEP-DOWN

PWM OUT2

1.0V TO 4.0V

500mA

PV2

PGND4

LX4

OUTS4

10µF

1.5µH

1.8V

2.2µF

STEP-DOWN

PWM OUT4

1.0V TO 4.0V

1.0A

PV4

PGND3

LX3

OUTS3

10µF

1.5µH

2.2µF

STEP-DOWN

PWM OUT3

1.0V TO 4.0V

500mA

PV3

2.65V

1.8V

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

www.maximintegrated.com Maxim Integrated

│

Package Information

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.

Note: Insert the desired suffix letter (from the Selector Guide) into the blank area "_" to indicate factory-selectable features.

/V denotes an automotive qualified part that conforms to AEC-Q100.

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

Ordering Information

Selector Guide*

*Contact factory for options that are not included. Factory-selectable features include:

● DC-DC voltages in 100mV steps between 1.0V and 4.0V.

● Spread spectrum enabled or disabled.

● UVM enabled or disabled.

● Number of cycles in active timeout period

● Independent current limit for each channel up to 1A.

PART FREQUENCY TEMP RANGE PIN-PACKAGE

MAX20021ATI_ / V+ 3.2MHz -40ºC to +125ºC 28 TQFN-EP*

MAX20022ATI_ / V+ 2.2MHz -40ºC to +125ºC 28 TQFN-EP*

PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.

28 TQFN-EP T2855+5 21-0140 90-0025

PART

CURRENT

CONFIGURATION DC-DC1 DC-DC2 DC-DC3 DC-DC4 SPREAD

SPECTRUM

FREQUENCY

(MHz) UVM

ACTIVE

TIMEOUT

PERIOD

(CYCLES)

CH1 CH2 CH3 CH4 VOUT (V)

MAX20021

MAX20021ATIA/V+ 1.0A 0.5A 0.5A 1.0A 3.30 1.25 2.65/1.80 1.80 Disabled 3.2MHz Enabled 20,480

MAX20021ATIB/V+ 1.0A 0.5A 0.5A 1.0A 3.30 1.25 2.65/1.80 1.80 Enabled 3.2MHz Enabled 20,480

MAX20021ATIC/V+ 1.0A 0.5A 0.5A 1.0A 3.30 1.20 2.65/1.80 1.50 Disabled 3.2MHz Enabled 20,480

MAX20021ATID/V+ 1.0A 0.5A 0.5A 1.0A 3.30 1.20 2.65/1.80 1.80 Disabled 3.2MHz Enabled 20,480

MAX20022

MAX20022ATIA+ 1.0A 1.0A 1.0A 1.0A Adjustable Adjustable Adjustable Adjustable Disabled 2.2MHz Disabled 256

MAX20022ATIA/V+ 1.0A 1.0A 1.0A 1.0A Adjustable Adjustable Adjustable Adjustable Disabled 2.2MHz Disabled 256

MAX20022ATIB+ 1.0A 1.0A 1.0A 1.0A Adjustable Adjustable Adjustable Adjustable Enabled 2.2MHz Disabled 256

MAX20022ATIB/V+ 1.0A 1.0A 1.0A 1.0A Adjustable Adjustable Adjustable Adjustable Enabled 2.2MHz Disabled 256

MAX20021/MAX20022 Automotive Quad, Low-Voltage

Step-Down DC-DC Converters

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.

Maxim 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 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 16

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 3/13 Initial release —

1 4/13 Removed future product reference for the MAX20022 15

2 12/13 Added AEC-Q100 reference to Ordering Information 15

3 8/14 Added two new MAX20021 options to Selector Guide 15

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