MAX20021 datasheet(11/16 Pages) MAXIM

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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.

ConnectPG_toalogicsupplywitha10kΩresistor.

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

1µs1µs

4µs

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