PJ3844B Просмотр технического описания (PDF) - Promax Johnton

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PJ3844B

High Performance Current Mode Controller

Promax Johnton 

FIGURE 20-EXTERNAL CLOCK

SYNCHRONIZATION

PJ3844B / PJ3845B

High Performance Current Mode Controller

FIGURE 21-EXTERNAL DUTY CYCLE CLAMP AND

MULTI UNIT SYNCHRONIZATION

The diode clamp is required if the Sync amplitude is large enough to

the cause the bottom side of CT to go more than 300mV below

ground.

1.44

f = (RA + R B )

DMAX

=

RB

R A + 2R B

FIGURE 22-ADJUSTABLE REDUCTION OF CLAMP

LEVEL

FIGURE 23-SOFT-START CIRCUIT

Vclmap

Ipk (max) = Rs

Where：≤ Vclmap ≤ 1.0V

Vclamp

=



1.67

R2 + 1

+

0.33

× 10−3



R1 R2

R1 + R2





 R1 

FIGURE 24-ADJUSTABLE BUFFERED REDUCTION

OF CLAMP LEVEL WITH SOFT-STAR

Isoft-Start=3600c in µF

FIGURE 25-CURRENT SENSING POWER MOSFET

Virtually lossless current sensing can be achieved with the

implementation of a SENSEFET power switch.For proper operation

during over current conditions.a reduction of the Ipk(max) clamp

level must be implemented.Refer to Figure 22 and 24.

9-14

2004/11. Rev B

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