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AS3658

Data Sheet Confidential - Detail ed Descri ption-Power Management Functions

Figure 7. DC/DC step up converter 1 with regulated output voltage (15V), and switch off function of output

voltage, to reduce shutdown current

As the output voltage is always on, an additional output transistor can be added to reduce shutdown current through

R1, R2 and the connected output circuit.

Note: A similar circuit can be used for step up converter 2.

8.1.2 StepUp1 Load Detection and Overcurrent Protection Circuit

This circuit protects the DCDC step up1 converter during short circuit and startup, by regulation of the output current.

An additional feature is the detection of a minimum output load of the Step-up converter. It is also possible to use this

circuit without the DCDC step up converter, by using the sense resistor only:

Detection circuit: If the voltage on Rsense exceeds VDETECT for more than 1msecond, or the DCDC Step up

converter is not in Pulseskip for more than 1 millisecond, the stepup1_det bit will be set.

Overcurrent protection: If the Overcurrent voltage VOVCURRENT has been exceeded by more than 5 msec the Bit

stpup1_oc will be set and can only reset, by switching off and on the Protection circuit by writing Stpup1_shortprot

0 – 1. If stepup1_oc is set the load will be disconnected, if Stpup1_oc_timeout=1

Table 7. StepUp1 protection/detection circuit parameters

Symbol

Parameter

Min

Typ

Max

Unit

Note

VDETECT

Detection Threshold

12.5

For Rsense=0.150

Ω =>

83mA typ.

VOVCURRENT

Overcurrent Threshold

rising

150

180

215

For Rsense=0.150

Ω =>

1.2A typ.

VOVhysteresis

Overcurrent Hysteresis

tOV_timeout

Overcurrent timeout

Interrupt and/or external PMOS

switching off after timeout

fclk_int = 2.2MHz

tdetect

Detection denounce

time

1ms

fclk_int = 2.2MHz

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