8

Block Diagram

+

-

+

-

+

-

+

-

V

V

V

V

V

V

V

V

V

V

V

OUVDELAY

OAOUT

OAM

Aux. Error Amp

A1

1.2V

+

5k

45k

D1

Output

Undervoltage

Timer

100k

P1

RUN1

RUN 2

G6

C9

PROGRAM

ENABLE

UVSD

DYLSET

FADJ

RAMP2

GATE2

GATE2B

A2

A2

G1

RUN 1

G7

G3

C1

G8

FREQ

TOO LOW

Aux.PWM

Comparator

Main PWM

Comparator

Sync Detection

Main 2nd Current

Threshold Comparator

Aux. 2nd Current

Threshold Comparator

Aux. Current

Limit Comparator

Main Current

Limit Comparator

C11

1.2V

V

Skip Two

Clock Pulses

SET

CLOCK

SET

CLOCK

Skip Two

Clock Pulses

G15

C17

C16

Skip2B

G14

G18

1.4V

GATE1

Gnd

RSFF

QR

F2

S

DRIVER

C10

C12

C13

OSC

IFSET

CLK1

CLK2

IDSET

C8

C5

OVSD

+

-

G13

C14

G16

G17

C15

DELAY

DELAY

G12

RUN2

RUN2

1.7V

+

DRIVER

Reset

Dominant

G11

G10

G9

VREF

ENABLE

5V

C2

RSFF

RQ

S

F1

Set Dominant

+

-

Over Voltage

Comparator

Comparator

Reset

Dominant

RSFF

Q

F3

S

R

Reset

Dominant

RSFF

Q

F4

S

R

+

-

C4

-

+

C7

Skip2B

ENABLE

Comparator

Under Voltage

Comparator

R

2R

G5

G4

DRIVER

TFF

T1

Q

+

0.13V

0.13V

+

START

STOP

R

2R

RUN1

Fault Latch

C3

+

-

FREQ

TOO HIGH

1.4V

5V

4.5

7.4/6.8V

1.4V

RAMP1

1.4V

Q

Theory of Application

Powering the IC

drivers are held in a low state. The CS5106 requires 1.5mA

nominal of startup current.

Startup

Assume the part is enabled and there are no over voltage

or under voltage faults present. Also, assume that all auxil-

iary and main regulated output voltages start at 0V. An

goes ÔhighÕ and ÔRUN1Õ will go ÔhighÕ, releasing GATE1

from its low state. After GATE1 is released, it begins

switching according to conditions set by the auxiliary con-

ÔhighÕ, releasing GATE2 and GATE2B from their low state.

GATE2 and GATE2B begin switching according to condi-

tions set by the main control loop and the main regulated

output begins to rise. See startup waveforms in Figure 1.

Soft Start

Soft start for the auxiliary power supply is accomplished

by placing a capacitor between OAOUT and Ground. The

error amplifier has 200µA of nominal of source current and

is ideal for setting up a Soft Start condition for the auxiliary

regulator. Care should be taken to make sure that the soft

start timing requirements are not in conflict with any tran-

sient load requirements for the auxiliary supply as large

capacitors on OAOUT will slow down the loop response.

Also, the Soft start capacitor must be chosen such that dur-

ing start or restart, both outputs will come into regulation

before the OUVDELAY timer trips. Soft Start for the main

supply is accomplished by charging soft start capacitor C6

through D5 and R7 at start up. After the main supply has

come into regulation C6 continues to charge and is discon-

nected from the feedback loop by D8.

Theory of Operation