P8/21

Rev. C, Sep 2005

ML1565

Pin Description

Pin16

FBSELSU

Pin17

FBSELSD

Pin18

FBSEL1

Pin19

OSC

Pin20

PGNDB

Pin21

LXSU

Pin22

OUTSUA

Pin23

SDOK

Pin24

COMP3

Pin25

FB3

Pin26

OUTSUB

Pin27

DL3

Pin28

DL2

Pin29

DL1

Pin30

GND

Pin31

COMP2

Pin32

FB2

Exposed

EP

Pad

Step-Up Feedback Select Pin. With FBSELSD = GND, OUTSU regulates to 3.35V. With FBSELSD =

OUTSU, FBSU regulates to a 1.25V threshold for use with external feedback resistors. This pin is high

impedance in shutdown.

Step-Down Feedback Select Pin. With FBSELSD = GND, FBSD regulates to 1.5V. With FBSELSD =

OUTSU, FBSD regulates to a 1.25V for use with external feedback resistors. This pin is high

impedance in shutdown.

Auxiliary Controller 1 Feedback Select Pin. With FBSEL1 = GND and FB1 regulates to 5V. With

FBSEL1=OUTSU, FB1 regulates to 1.25V for use with external feedback resistors. This pin is high

impedance in shutdown.

Oscillator Control. Connect a timing capacitor from OSC to GND and a timing resistor from OSC to

OUTSU to set the oscillator frequency between 100kHz and 1MHz. This pin is high impedance in

shutdown.

Power Ground. Connect PGNDA and PGNDB together and to GND with short trace as close to the IC

as possible.

Step-Up Converter Power-Switching Node. Connect LXSU to the step-up converter inductor. LXSU is

high impedance in shutdown.

Step-Up Converter Output. OUTSUA is the power output of the step-up converter. Connect OUTSUA

to OUTSUB at the IC.

This open-drain output goes high impedance when the step-down has successfully completed

soft-start.

Auxiliary Controller 3 Compensation Node. Connect a series resistor-capacitor form COMP3 to GND

to compensate the control loop. COMP3 is actively driven to GND in shutdown and thermal limit.

Auxiliary Controller 3 Feedback Input. Connect a resistive voltage-divider from the output voltage to

FB3 to GND. The FB3 feedback threshold is 1.25V. This pin is high impedance in shutdown.

Step-Up Converter Output. OUTSUB powers the ML1565 and is the sense input when FBSELSU is

GND and the output is 3.3V. Connect OUTSUA to OUTSUB.

Auxiliary Controller 3 Gate-Drive Output. Connect the gate of an N-channel MOSFET to DL3. DL3

swings from GND to OUTSU and supplies up to 500mA. DL3 is driven to GND in shutdown and

thermal limit.

Auxiliary Controller 2 Gate-Drive Output. Connect the gate of an N-channel MOSFET to DL2. DL2

swings from GND to OUTSU and supplies up to 500mA. DL2 is driven to GND in shutdown and

thermal limit.

Auxiliary Controller 1 Gate-Drive Output. Connect the gate of an N-channel MOSFET to DL1. DL1

swings from GND to OUTSU and supplies up to 500mA. DL1 is driven to GND in shutdown and

thermal limit.

Quiet Ground. Connect GND to PGND as close to the IC as possible.

Auxiliary Controller 2 compensation Node. Connect a series resistor-capacitor from COMP2 to GND to

compensate the control loop. COMP2 is actively driven to GND in shutdown and thermal limit.

Auxiliary Controller 2 Feedback Input. Connect a resistive voltage-divider form the output voltage to

FB2 to GND to set the output voltage. The FB2 feedback threshold is 1.25V. This pin is high

impedance in shutdown.

Exposed Underside Metal Pad. This pad must be soldered to the PC board to achieve package

thermal and mechanical ratings. The exposed pad is electrically connected to GND.