CS5106 Cherry Semiconductor Corporation, CS5106 Datasheet - Page 8

• Manufacturer Part Number: CS5106
• Description: Multi-Feature/ Synchronous plus Auxiliary PWM Controller
• Manufacturer: Cherry Semiconductor Corporation

Powering the IC
The IC has one supply, V
used for a bootstrapped supply the diode between V
V
from V
V
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
8V, Zener referenced supply is typically applied to V
When V
the OSC begins switching. If the V
sively loaded such that V
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-
trol loop and the auxiliary supply, V
When V
OUVDELAY
CC
CC
OAOUT
. During abnormal operating conditions, all GATE
is forward biased, and the IC will derive its power
RAMP1
GATE1
OAM
V
V
V
5REF
SS
Gnd
I
V
SS
FB1
LIM1
CC
CC
SS
. The internal logic monitors the supply voltage,
> V
exceeds 7.5V, the 5V reference is enabled and
D1
CC
V
DRIVER
+ V(D1), P1 turns on and ÔRUN2Õ goes
START
STOP
+
-
7.4/6.8V
A1
0.13V
Theory of Operation
P1
+
-
100k
Aux. Error Amp
45k
RUN1
G9
5k
CC
5REF
ENABLE
V
+
1.2V +
REF =
, and one Ground lead. If V
V
Dominant
RUN1
< 4.5V nominal, ÔV
Reset
RSFF
VREF
Q
5V
F4
2R
G14
R
S
V
5REF
CC
R
V
4.5
Output
Undervoltage
Timer
SS
V
REFOK
Aux. 2nd Current
Threshold Comparator
G10
G6
Skip2B
V
begins to rise.
Aux. Current
Limit Comparator
lead is not exces-
Aux.PWM
Comparator
+
-
5V
C9
Comparator
G5
Skip Two
Clock Pulses
V
REF
C2
+
-
CLOCK
RUN 2
OK
C12
C10
SET
C16
+
REF
-
+
-
+
-
Theory of Application
C4
C7
+
+
-
-
OKÕ
1.2V
1.4V
SS
Set Dominant
1.4V
CC
Block Diagram
V
V
RSFF
R
S
SS
and
.
F1
V
Q
is
C17
+
-
CLOCK
T
+
Skip Two
Clock Pulses
SET
-
C13
C11
+
-
+
RUN 1
PERIOD
V
8
Main 2nd Current
Threshold Comparator
Main Current
Limit Comparator
1.5V
Main PWM
Comparator
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.
V
REFOK
Fault Latch
+
-
A2
Dominant
Skip2B
Q
Reset
RSFF
F2
G11
R
S
CLK1
CLK2
IFSET
V
SS
G18
OSC
SYNC
G15
Dominant
R
SYNC
Reset
S
R
RSFF
G4
F3
IDSET
A2
OUT
Q
Q
G1
+
-
IN
2R
V
Comparator
SS
V
G17
Restart
G13
1.4V
G7
+
RUN2
G8
C15
C14
Under Voltage
Comparator
Sync Detection
+
-
+
Over Voltage
Comparator
-
RUN2
DELAY
DELAY
0.13V
ENABLE
Comparator
TOO HIGH
TOO LOW
G3
FREQ
FREQ
G16
G12
1.7V
V
C1
C3
C5
C8
+
DRIVER
DRIVER
+
+
+
-
+
-
-
-
Q
TFF
T1
1.4V
5V
V
V
OVSD
GATE2B
PROGRAM
ENABLE
UVSD
SYNC
SYNC
DYLSET
FADJ
RAMP2
V
GATE2
I
LIM2
FB2
IN
OUT