MAX20029BATIBV datasheet(12/17 Pages) MAXIM

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Spread-Spectrum Option

The PMICs feature a linear spread-spectrum (SS)

operation, 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 3). 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. 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

185°C (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 15°C. The IC goes through a standard power-up

sequence as defined in the Soft-Start section.

Applications Information

Adjustable Output-Voltage Option

The MAX20029/MAX20029B PMICs feature adjustable

output voltages (see the Selector Guide for more details),

which allows the customer to set the outputs to any volt-

age between 1.0V and VPV_ - 0.5V (up to 4.0V). Connect

a resistive divider from output (VOUT_)toOUTS_toGND

to set the output voltage (see Figure 4).SelectR2(OUTS_

totheGNDresistor)≤100kΩ.CalculateR1(VOUT_ to the

OUTS_resistor)withthefollowingequation:

OUT_

OUTS_

R1 R2









−









where VOUTS_ = 1.0V (see the Electrical Characteristics

table). The output voltage is nominal at 50% load current.

The external feedback resistive divider must be frequency

compensated for proper operation. Place a capacitor

across R1 in the resistive divider network. Use the

following equation to determine the value of the capacitor:

1, C1 C

else C1 C, where C 15pF



= 



ConnectOUTS_toVOUT_ for a fixed 1.0V output voltage.

Figure 3. Effect of Spread Spectrum on Internal Oscillator

Figure 4. Adjustable Output-Voltage Configuration

MAX20029

MAX20029B

VOUT_

OUTS_

fSW + 3%

fSW

t + 667µs

TIME

t + 1.334ms

INTERNAL

OSCILLATOR

FREQUENCY

MAX20029/MAX20029B/

MAX20029C/MAX20029D

Automotive Quad/Triple Low-Voltage

Step-Down DC-DC Converters

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