2A, 40V Step-Down DC-DC Converter with

Dynamic Output-Voltage Programming

8

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Pin Description

PIN

NAME

FUNCTION

1

COMP

Voltage-Error-Amplifier Output. Connect COMP to the necessary compensation feedback network.

2FB

Feedback Regulation Point. Connect to the center tap of an external resistor-divider connected between

the output and GND to set the output voltage. The FB voltage regulates to the voltage applied to REFIN.

3

ON/OFF

ON/OFF Control. The ON/OFF rising threshold is set to approximately 1.225V. Connect to the center tap of

a resistive divider connected between IN and GND to set the turn-on (rising) threshold. Connect ON/OFF to

UVLO threshold. ON/OFF can be used for power-supply sequencing.

4

REFOUT

0.98V Reference Voltage Output. Bypass REFOUT to GND with a 0.1µF ceramic capacitor. REFOUT is to

be used only with REFIN. It is not to be used to power any other external circuitry.

5

SS

Soft-Start. Connect a 0.01µF or greater ceramic capacitor from SS to GND. See the Soft-Start (SS) section.

6

REFIN

Connect REFIN to REFOUT to use the internal 1V reference. See the Reference Input and Output (REFIN,

REOUT) section.

7

FSEL

8

SYNC

Oscillator Synchronization Input. SYNC can be driven by an external 100kHz to 500kHz clock to

synchronize the MAX15020’s switching frequency. Connect SYNC to GND to disable the synchronization

function. When using SYNC, connect FSEL to REG.

9

DVREG

Power Supply for Internal Digital Circuitry. Connect a 10Ω resistor from REG to DVREG. Connect DVREG to

the anode of the boost diode, D2 in Figure 2. Bypass DVREG to GND with at least a 1µF ceramic capacitor.

10

PGND

Power-Ground Connection. Connect the input filter capacitor’s negative terminal, the anode of the

freewheeling diode, and the output filter capacitor’s return to PGND. Connect externally to GND at a single

point near the input bypass capacitor’s return terminal.

11

N.C.

No Connection. Leave unconnected or connect to GND

12

BST

High-Side Gate Driver Supply. Connect BST to the cathode of the boost diode and to the positive terminal

of the boost capacitor.

13, 14, 15

LX

Source Connection of Internal High-Side Switch. Connect the inductor and rectifier diode’s cathode to LX.

16, 17, 18

IN

Supply Input Connection. Connect to an external voltage source from 7.5V to 40V.

19

REG

8V Internal Regulator Output. Bypass to GND with at least a 1µF ceramic capacitor. Do not use REG to

power external circuitry.

20

GND

Ground Connection. Solder the exposed pad to a large GND plane. Connect GND and PGND together at

one point near the input bypass capacitor return terminal.

—EP

Exposed Pad. Connect EP to GND. Connecting EP does not remove the requirement for proper ground

connections to the appropriate pins. See the PCB Layout and Routing section.