AS1337 datasheet(9/14 Pages) AMSCO

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AS1337

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

Shutdown

When pin EN is low the AS1337 is switched off and <1µA current is drawn from battery; when pin EN is high the device

is switched on. If EN is driven from a logic-level output, the logic high-level (on) should be referenced to VOUT to avoid

intermittently switching the device on.

Note: If pin EN is not used, it should be connected directly to pin VOUT.

Caution: Because of the feedthrough the output voltage is the same as the input voltage during shutdown. If VIN >

VOUT the output voltage will jump to the value of the input voltage when the device switches into shut-

down. During normal operation the device is in down conversion mode.

Shutdown Battery Feedthrough (AS1337A)

In shutdown the battery input of the AS1337A is connected to the output through the inductor and the small internal

synchronous rectifier P-FET. This allows the input battery to provide backup power for devices such as an idle micro-

controller, memory, or real-time-clock, without the usual diode forward drop. In this way a separate backup battery is

not needed.

Shutdown Battery Disconnect (AS1337B)

The AS1337B is designed to allow true output disconnect by opening both P-channel MOSFET rectifiers. During Shut-

down VOUT is discharged via the internal NMOS transistor and connected to GND.

POK Function

The POK output indicates if the output voltage is within 88% (typ.) of the nominal voltage level. As long as the output

voltage is within regulation the open-drain POK output is high impedance. The POK output can be tied to VIN or to

VOUT or to any external voltage up to VIN or VOUT via a pull-up resistance (see Figure 1 on page 1). If the output volt-

age drops below 88% (typ.) of the nominal voltage the POK pin is pulled to GND.

Note: It is important to consider that in shutdown mode the POK output is pulled to VIN in order to save current.

AS1337 데이터시트(PDF) 9 Page - ams AG