Power-Good Indicator (PGOOD)

The device includes an open-drain power good output

that indicates the output voltage status. PGOOD goes

high impedance when the output voltage is above 93.5%

of the target value, and goes low when the output voltage

is below 90% of the target value.

Startup Into a Prebiased Output

The device is capable of soft-starting into a prebiased

output without discharging the output. The device

ramps up the output voltage monotonically from the

prebiased level to the target level during the soft-start

period if the prebiased voltage is less than the target

output voltage. If the prebiased voltage is more than the

target output voltage, no switching happens during the

soft-start period. The device operation after the completion

of the soft-start period under prebiased output condition

(where the prebiased voltage is higher than the target

output voltage) depends on the PWM/skip mode. In PWM

Mode, the device tries to regulate the output voltage to the

target level by sinking current from the prebiased source.

In skip mode, the device does not initiate switching until

the output voltage falls below the target output voltage.

100% Duty-Cycle Operation

The device can provide 100% duty-cycle operation. In

this mode, the high-side switch is constantly turned on,

while the low-side switch is turned off. This is particularly

useful in battery-powered applications to achieve longest

operation time by taking full advantage of the whole

battery-voltage range. The minimum input voltage to

maintain the output-voltage regulation can be calculated

as:

where,

the output inductor DCR

Undervoltage Lockout

The device features an integrated input undervoltage

lockout (UVLO) feature that turns the device on/off based

on the voltage at the IN pin. The device turns on if the IN

of 2.6V (typ) (assuming EN is at logic-high) and turns off

Overcurrent Protection

The device features a robust overcurrent-protection

scheme that protects the device and inductor under

overload and output short-circuit conditions. A cycle-by-

cycle peak current limit turns off the high-side MOSFET

and turns on the low-side MOSFET whenever the high-

side MOSFET current exceeds the internal peak current

limit of 1.45A (typ). The low-side MOSFET remains on

until the next clock cycle. The high-side MOSFET is

turned on again, if the inductor current is less than the

valley current limit at the next clock rising edge. Otherwise,

the low-side MOSFET is kept on for the next clock cycle

as well. Under severe overload conditions, the current will

not exceed 1.45A. If the overload condition is removed,

the part recovers smoothly to target output voltage with no

overshoot.

Thermal Shutdown

Thermal-shutdown protection limits the total power

dissipation in the device. When the device junction

temperature exceeds +165°C, an on-chip thermal

sensor shuts down the device, allowing it to cool. The

thermal sensor turns the device on again after the junction

temperature cools by 10°C.

MAX17620

4MHz, Miniature 600mA, Synchronous Step-Down

DC-DC Converter with Integrated MOSFETs

www.maximintegrated.com

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