AP66300

Document number: DS43722 Rev. 2 - 2

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August 2022

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AP66300

Pin Descriptions

Pin Name

Pin Number

Function

BIAS

1

The internal regulator will draw current from BIAS instead of VIN when BIAS is tied to a voltage higher than 4.4V.

For output voltages of 5V to 15V this pin should be tied to VOUT. If this pin is tied to a supply other than VOUT use a

1µF local bypass capacitor on this pin. If no supply is available, tie to PGND.

VCC

2

Internal power supply output pin to connect an additional capacitor. Connect a

1μF (typical) capacitor as close as

possible to the VCC and PGND. This pin is not active when EN is low.

VIN

3, 4

Power Input. VIN supplies the power to the IC, as well as the step-down converter switches. Drive VIN with a

3.8V to 60V power source. Bypass VIN to GND with a suitable large capacitor to eliminate noise on the input to

the IC. See Input Capacitor.

BST

5

High-Side Gate Drive Boost Input. BST supplies the drive for the high-side N-Channel MOSFET a 0.1µF or

greater capacitor from SW to BST to power the high side switch.

SW

6, 7

Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter

from SW to the output load. Note that a capacitor is required from SW to BST to power the high-side switch.

PGND

8, 9

Power Ground. Connect PGND plane and EXPOSED PAD with as many via for thermal and efficiency

performance.

EN

10

Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator; low to

turn it off. Connect directly to VIN for automatic startup.

FS

11

This pin set the oscillator switching frequency, using a resistor, RFS, from FS pin to GND. The frequency of

operation may be programmed from 300kHz to 2.5MHz. Connect FS to VCC or HIGH for a default frequency of

500kHz.

MSYNC

12

Connect MSYNC to VCC or HIGH for forced PWM. Connect MSYNC to GND for PFM operation. Apply an

external clock source for synchronization with positive edge trigger and PWM.

PG

13

Open drain power-good output that is pulled to GND when the output voltage is out of its regulation limits or

during soft-start interval. There is an internal 5M

Ω pull-up resistor.

SS/TR

14

Soft-start pin for the regulator. The SS/TR pin controls the soft-start and sequence of the output. A single

capacitor from SS/TR to GND determines the output ramp rate. See the “Output Tracking and Sequencing”

section for more application detail about soft-start, output tracking, and sequencing. If SS is tied to VCC, then an

internal soft-start of 2ms will be used.

FB

15

Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage divider

connected to it from the output voltage. The feedback threshold is 0.8V. See Setting the Output Voltage.

GND

16

Analog ground that is used for control. Single point connection to the EPAD.