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AS1335

Datasheet - D e t a i l e d D e s c r i p t i o n

8 Detailed Description

The AS1335 is a high-efficiency buck converter that uses a constant-frequency current-mode architecture. The device

contains two internal MOSFET switches and is available with a user-adjustable output voltage.

Figure 18. AS1335 - Block Diagram

Main Control Loop

During normal operation, the internal top power MOSFET is turned on each cycle when the oscillator sets the RS latch.

relative to the internal 0.6V reference, causing the error amplifier’s output voltage to increase until the average inductor

current matches the new load current.

When the top MOSFET is off, the bottom MOSFET is turned on until the inductor current starts to reverse as indicated

by the current reversal comparator (IRCMP), or the next clock cycle begins. The over-voltage detection comparator

(OVDET) guards against transient overshoots >7.8% by turning the main switch off and keeping it off until the transient

is removed.

AS1335

OSC

Frequency

Shift

0.6V

Reference

+

–

Error

Amp

Shutdown

Ramp

Compensator

0.6V

OSCN

Digital

Logic

0.6V +

0.6V -

–

OVDET

+

–

+

–

ICOMP

+

–

IRCMP

+

Anti-

Shoot

Through

Main

EN

FB

VIN

SW

GND

Power-OK

Compare

Logic

RSI

POK