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AS7620

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

8 Detailed Description

Figure 17. System Diagram of AS7620-A with Early Power Fail Warning

8.1 Shut Down

The device can be shut down by providing a voltage lower than 1V at the SHDN pin (7). In this condition, the consumption is only 1µA (typ). The

AS7620 is providing an internally regulated pull-up circuit. No external pull-up resistor shall be used, which could otherwise damage the

shutdown input. Connect the SHDN input directly to an open drain port only.

8.2 Soft Start

The device implements a soft start by limiting the inrush current into the output choke. Initially, the internal PMOS is turned on until the current

reaches the programmed current limit (see Current Limit on page 9) and then is immediately turned off. It will be turned on again when the

current limit only.

8.3 Regulation

Both AS7620-A and AS7620-B are based on a hysteretic control method. Moreover, the switch current is monitored to make the converter

always work in discontinuous current mode (DCM). The advantages of this type of control system can be summarized as following:

High efficiency even at light load

Intrinsically stable

Simplicity

Readiness during the load transient

100µH; C=10µF - 100µF) and setting the CL threshold according to the load, the on time is normally terminated by the CL intervention and the

Table 4. AS7620 Output Voltage Options

AS7620

AS7620A-BQFT

AS7620B-BQFT

ADJ.

3.3V

2.2µF

100µF

10µH

3.6V to 32V

FB

PF

PG

AS7620-A

SHDN

3.3V