ADP2442ACPZ-R7 datasheet(17/36 Pages) AD

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Data Sheet

ADP2442

Rev. B | Page 17 of 36

ADJUSTABLE FREQUENCY

The ADP2442 features a programmable oscillator frequency with

a resistor connected between the FREQ and AGND pins.

At power-up, the FREQ pin is forced to 1.2 V and current flows

from the FREQ pin to AGND; the current value is based on the

resistor value on the FREQ pin. Next, the same current replicates in

the oscillator to set the switching frequency. Note that the resistor

connected to the FREQ pin must be placed as close as possible

to the FREQ pin (see the Applications Information section for

more information).

POWER GOOD

The PGOOD pin is an open-drain output that indicates the

status of the output voltage. When the voltage of the FB pin

is between 92% and 109% of the internal reference voltage,

the PGOOD output pulls high, provided there is a pull-up resistor

connected to the pin. When the voltage of the FB pin is not

within this range, the PGOOD output pulls low to AGND. The

PGOOD threshold is shown in Figure 54.

Likewise, the PGOOD pin is pulled low to AGND when



The input voltage is below the internal UVLO threshold.



The EN pin is low.



A thermal shutdown event has occurred.

Figure 54. PGOOD Threshold

In a typical application, a pull-up resistor connected between the

PGOOD pin and an external supply is used to generate a logic

signal. This pull-up resistor must range in value from 30 kΩ to

100 kΩ, and the external supply must be less than 5.5 V.

MODE OF OPERATION

The SYNC/MODE pin is a multifunctional pin. The fixed

frequency mode is enabled when SYNC/MODE is connected to

VCC or a high logic. When SYNC/MODE connects to AGND,

pulse skip mode enables. The external clock can be applied for

synchronization.

Table 5. SYNC/MODE Pin Mode of Operation

SYNC/MODE Pin

Mode of Operation

Low

Pulse skip mode

High

Forced fixed frequency mode

Clock Signal

Forced fixed frequency mode

EXTERNAL SYNCHRONIZATION

The external synchronization feature allows the switching

frequency of the device to be synchronized to an external clock.

The SYNC/MODE input accepts a logic level clock input ranging

from 300 kHz to 1 MHz (minimum pulse width = 100 ns) and has

high input impedance. For best practices, it is recommended

that the set frequency (set by the resistor at the FREQ pin) be

within ±30% of the expected clock frequency to ensure stable,

reliable, and seamless operation with or without an external

SYNC/MODE clock. When the ADP2442 is synchronized to an

external clock, the regulator switching frequency changes to the

external clock frequency.

SOFT START

The ADP2442 has an internal soft start feature that allows the

output voltage to ramp up in a controlled manner, limiting the

inrush current during startup. The ADP2442 internal soft start

time is 2 ms.

Figure 55. Internal Soft Start

UNDERVOLTAGE LOCKOUT

The undervoltage lockout (UVLO) function prevents the IC

from turning on when the input voltage is below the specified

operating range to avoid an undesired operating mode. If the

input voltage drops below the specified range, the UVLO function

shuts off the device. The rising input voltage threshold for the

UVLO function is 4.2 V with 200 mV hysteresis. The 200 mV of

hysteresis prevents the regulator from turning on and off repeatedly

when there is a slow voltage ramp on the VIN pin.

PRECISION ENABLE/SHUTDOWN

The ADP2442 features a precision enable pin (EN) to enable or

shutdown the device. The ±5% accuracy lends itself to using a

resistor divider from the VIN pin (or another external supply) to

program a desired UVLO threshold that is higher than the fixed

internal UVLO of 4.2 V. The hysteresis is 100 mV.

If a resistor divider is not used, apply a logic signal instead. A

logic high enables the device, and a logic low forces the device

into shutdown mode.

VOUT RISING

VOUT FALLING

110

116

POWER

GOOD

OVERVOLTAGE

UNDERVOLTAGE

PGOOD

UNDERVOLTAGE

POWER

GOOD

100

T 26.00%

CH1 2.00V BW

CH2 10.0V

CH3 5.00V BW

M1.00ms

A CH1

3.44V

VOUT

VIN = 24V

VOUT = 5V

fSW = 700kHz

LOAD = NO LOAD

SYNC/MODE = AGND

INTERNAL SS TIME

2.18ms

ADP2442ACPZ-R7 Datasheet(PDF) 17 Page - Analog Devices

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