SW1

Overvoltage

Comperator

Comparator

Error

Amplifier

N-MOS

SW2

D

S

CurrentSampling

&

SlopeCompensation

CurrentLimit

&

Softstart

ControlLogic

PGND1

PGND2

OS

1.24V

750kHz

Oscillator

COMP

FB1

1.24V

Overvoltage

Comparator

Shortcircuit

Comparator

1.24V + 3%

100 mV

SS

AVIN

GD

D

S

450W

RHVS

HVS

VL

6V

10kW

Switch

Soft-Start (Boost Converter)

2

2

inductor

SS

SS

inductor

I

0.43

mA

0.43

t

mA

=

C

=

t

C

V

I

V

D

´ D

´

´

D

D

(5)

Compensation (Boost Converter)

1

2

4

5

Z

f

R

C

p

=

´

´

´

(6)

TPS65166

Figure 24. Boost Converter Block Diagram

To avoid high inrush current during start-up an internal soft-start is implemented. The soft-start time is set by an

external capacitor connected to the SS pin. The capacitor is charged with a constant current of typically 10

µA,

which increases the voltage at the SS pin. The internal switch current limit is proportional to the SS pin voltage

soft-start capacitor value the longer the soft-start time. For a 100nF capacitor at the SS pin, the current limit is

reached after 0.9ms. An estimation of the current limit slope

following formulas.

The regulator loop can be compensated by adjusting the external components connected to the COMP pin. The

typical value of R4 = 39k

Ω and C5 = 1nF is appropriate for most applications. The below formula calculates at

what frequency the resistor R4 increases the high frequency gain.

Copyright © 2009, Texas Instruments Incorporated

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