A7985ATR datasheet(39/44 Pages) STMICROELECTRONICS

Part #	A7985ATR

Description	2 A step-down switching regulator for automotive applications

PDF	44 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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39 / 44 page

DocID023128 Rev 5

39/44

A7985A

Application ideas

Figure 36. Inverting buck-boost regulator

The GND pin of the device is connected to the output voltage so, given the output voltage,

the input voltage range is limited by the maximum voltage the device can withstand across

VCC and GND (38 V). Therefore, if the output is -5 V, the input voltage can range from 4.5 V

to 33 V.

As in the positive buck-boost, the maximum output current according to application

conditions is shown in Figure 37. The dashed line considers a more accurate estimation of

the duty cycles given by Equation 47, where power losses across diodes and the internal

Power MOSFET are taken into account.

Equation 47

Figure 37. Maximum output current according to switch max. peak current (2.0 A):

VO = -5 V

VOUT VD

–

– IN VSW VOUT VD

–

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A7985ATR Datasheet(PDF) 39 Page - STMicroelectronics