Connection Diagrams

Top View

30067304

16-Lead TSSOP EP

NS Package Number MXA16A

Top View

30067366

20-Lead TSSOP EP

NS Package Number MXA20A

Ordering Information

Order Number

Spec.

Package Type

NSC Package

Drawing

Supplied As

LM3421MH

NOPB

TSSOP-16 EP

MXA16A

92 Units, Rail

LM3421MHX

NOPB

TSSOP-16 EP

MXA16A

2500 Units, Tape and Reel

LM3423MH

NOPB

TSSOP-20 EP

MXA20A

73 Units, Rail

LM3423MHX

NOPB

TSSOP-20 EP

MXA20A

2500 Units, Tape and Reel

Pin Descriptions

LM3423

LM3421

Name

Function

1

1

V

IN

Power supply input (4.5V-75V). Bypass with 100nF capacitor to AGND as close to the device

as possible in the circuit board layout.

2

2

EN

Enable: Pull to ground for zero current shutdown. Tie directly to V

4.1V.

3

3

COMP

Compensation: PWM controller error amplifier compensation pin. This pin connects through

a series resistor-capacitor network to AGND.

4

4

CSH

Current Sense High: Output of the high side sense amplifier and input to the main regulation

loop error amplifier.

5

5

RCT

Resistor Capacitor Timing: External RC network sets the predictive “off-time” and thus the

switching frequency. The RC network should be placed as close to the device as possible in

the circuit board layout.

6

6

AGND

Analog Ground: The proper place to connect the compensation and timing capacitor returns.

This pin should be connected via the circuit board to the PGND pin through the EP copper

circuit board pad.

7

7

OVP

Over-Voltage Protection sense input: 1.24V threshold with hysteresis that is user

programmable by the selection of the OVP Over-Voltage Lock-Out (OVLO) resistor divider

network.

8

8

nDIM

Not DIM input: Dual function pin. Primarily used as the Pulse Width Modulation (PWM) input.

When driven with a resistor divider from V

V

the UVLO resistor divider network. The PWM and UVLO functions can be performed

simultaneously.

9

-

FLT

Fault flag: This is an N-channel MOSFET open drain output. The FLT pin transitions to the

high (open) state once the Fault Timer has timed out and latched the controller off.

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