Preliminary

Rev.01

11/16

EP1551

pin is high impedance in shutdown.

20

PGNDB

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

close to the IC as possible.

21

LXSU

Step-up Converter Power-Switching Node. Connect LXSU to the Step-up converter

inductor. LXSU is high impedance in shutdown.

22

OUTSUA

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

Connect OUTSUA to OUTSUB at the IC.

23

SDOK

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

completed soft-start.

24

COMP3

Auxiliary Controller 3 Compensation Node. Connect a series resistor-capacitor from

COMP3 to GND to compensate the control loop. COMP3 is actively driven to GND in

shutdown and thermal limit.

25

FB3

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.

26

OUTSUB

Step-up Converter Output. OUTSUB powers the EP1551 and is the sense input when

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

27

DL3

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.

28

DL2

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.

29

DL1

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.

30

GND

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

31

COMP2

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.

32

FB2

Auxiliary Controller 2 Feedback Input. Connect a resistive voltage-divider from 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

Pad

EP

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.