AS1329_13 datasheet(2/20 Pages) AMSCO

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AS1329

Datasheet - P i n A s s i g n m e n t s

4 Pin Assignments

Figure 2. Pin Assignments (Top View)

4.1 Pin Descriptions

Table 2. Pin Descriptions

Pin Number

Pin Name

Description

Switch Pin. Connect an inductor between this pin and VIN. Keep the PCB trace lengths as

short and wide as is practical to reduce EMI and voltage overshoot. If the inductor current

falls to zero, or pin SHDNN is low, an internal 100

Ω anti-ringing switch is connected from this

pin to VIN to minimize EMI.

Note:

An optional Schottky diode can be connected between this pin and VOUT.

GND

Signal and Power Ground. Provide a short, direct PCB path between this pin and the

negative side of the output capacitor(s).

Feedback Pin. Feedback input to the gm error amplifier. Connect a resistor divider tap to this

pin. The output voltage can be adjusted from 2.5 to 5V by: VOUT = 1.23V[1 + (R1/R2)]

SHDNN

Shutdown Pin. Logic controlled shutdown input.

1 = Normal operation, 1.2MHz typical operating frequency.

0 = Shutdown; quiescent current <1µA. If SHDNN is undefined, pin SW may ring.

Note:

In a typical application, SHDNN should be connected to VIN through a 1M

Ω pull-up

resistor.

VOUT

Output Voltage Sense Input and Drain of the Internal PMOS Synchronous Rectifier.

Bias is derived from VOUT when VOUT exceeds VIN. PCB trace length from VOUT to the

output filter capacitor(s) should be as short and wide as is practical.

VIN

Input Voltage. The AS1329 gets its start-up bias from VIN unless VOUT exceeds VIN, in

which case the bias is derived from VOUT. Thus, once started, operation is completely

independent from VIN. Operation is only limited by the output power level and the internal

series resistance of the supply.

AS1329

GND

6 VIN

5 VOUT

4 SHDNN

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