AP3581A/B/C

Document number: DS41552 Rev. 2 - 4

2 of 13

www.diodes.com

November 2018

© Diodes Incorporated

AP3581A/B/C

PART OBSOLETE

– NO ALTERNATE PART

Typical Applications Circuit

VCC

BOOT

UGATE

LGATE

PHASE

OPS

COMP/EN

FB

Enable

Disable

2

1

8

4

3

6

7

5

R1

10k

R2

5.1k/10k

GND

9

VIN=12V

VOUT=1.2V

Q1

Q2

Q3

L1

1.0

μH

C6

1000

μF/6.3V

C7

1000

μF/6.3V

R3

10k

C3

10nF

R5

C5 1

mF

R4 2

W

C4

0.1

mF

C1

10μF/25V

C2

220

μF/25V

Pin Descriptions

Pin Number

Pin Name

Function

1

BOOT

Bootstrap pin. Connect a bootstrap capacitor (Typically from 0.1

μF to 0.47μF) from this

pin to PHASE pin to create a BOOT voltage suitable to drive a standard N-Channel

MOSFET

2

UGATE

Upper-gate drive pin. Connect this pin to the upper MOSFET gate providing the gate

drive. This pin is monitored by the adaptive shoot-through protection circuitry to

determine when the upper MOSFET has been turned off

3

OPS

Over-current setting pin. Connecting a resistor (ROCSET) between OPS and GND to set

the over-current trigger point

4

LGATE

Lower-gate drive pin. Connect LGATE to the lower MOSFET gate providing the gate

drive for the lower MOSFET. This pin is monitored by the adaptive shoot-through

protection circuitry to determine when the lower MOSFET has turned off

5

VCC

Bias supply pin. Provides a 5V or 12V bias supply for the chip from this pin. The pin

should be bypassed with a capacitor to GND

6

FB

Feedback pin. This pin is the inverting input of the internal error amplifier. Use FB pin,

in combination with the COMP pin, to compensate the voltage control feedback loop

of the converter. A resistor divider from output to GND is used to set the output

voltage

7

COMP/EN

Compensation and disable pin, this pin is the output of the error amplifier. Pull COMP

pin low will shut down the IC

8

PHASE

PHASE pin. This pin connects to the source of the upper MOSFET and the drain of

the lower MOSFET. This pin is also monitored by the adaptive shoot-through

protection circuitry to determine when the upper MOSFET has turned off

9

GND

Exposed pad as ground pin. Represents the signal and power ground for the IC. Tie

this pin to the ground island/plane through the lowest impedance connection available