AST1S31HF datasheet(10/33 Pages) STMICROELECTRONICS

Part #	AST1S31HF

Description	Internal soft-start and enable

PDF	33 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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10 / 33 page

Functional description

AST1S31HF

10/33

DocID026968 Rev 2

6.1

Output voltage adjustment

The error amplifier reference voltage is 0.8 V typical. The output voltage is adjusted

according to the following formula (see Figure 1 on page 1):

Equation 1

The internal architecture of the device requires a minimum off time, cycle by cycle, for the

output voltage regulation. The minimum off time is typically equal to 66 ns.

The control loop compensates for conversion losses with duty cycle control. Since the

power losses are proportional to the delivered output power, the duty cycle increases with

the load current request.

Figure 4 shows at different loading conditions the maximum regulated output voltage over

the input voltage range.

Figure 4. Maximum output voltage over loading conditions

VOUT

0.8

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AST1S31HF Datasheet(PDF) 10 Page - STMicroelectronics