DAP005 datasheet(17/39 Pages) STMICROELECTRONICS

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DAP005

Application information

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An important advantage of this technique is that the overvoltage level can be set

independently of the regulated output voltage: the latter depends on the ratio of R1 to R2,

the former on the individual value of R1. Another advantage is the precision: the tolerance of

the detection current is 12.5%, which means 12.5% tolerance on the

∆V

O. Since it is usually

much smaller than Vo, the tolerance on the absolute value will be proportionally reduced.

Example: VO = 400V, ∆VO = 40V.

Then: R1 = 40V/20µA = 2M

Ω ; R2 = 2.5·2MΩ·/(400-2.5) = 12.58kΩ.

The tolerance on the OVP level due to the DAP005 will be 40·0.125 = 5 V, that is ± 1.14 %.

When either OVP is activated the quiescent consumption is reduced to minimize the

discharge of the Vcc capacitor.

Figure 34. Output voltage setting, OVP and FFP functions: internal block diagram

2.5V

DAP005

INV

COMP

E/A

Frequency

Compensation

PFC_OK

ITBO

2.25V

Static OVP

Dynamic OVP

20 µA

Vout

{R1a

R1b

9.5V

FAULT (latched)

TBO

FUNCTION

{R3a

R3b

FAULT (not latched)

0.26V

9.5V

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