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Rev. A.2 - J uly., 2004
HPW 7095/ A
17
Copyright
HIPAC Semiconductor, Inc.
www.hipacsemi.com
Function Descriptions (Cont.)
Output Switch Control Circuit
The output switch control circuit outputs a signal to
control external p-channel MOSFETs for preventing
reactive current flow to external step-up circuits on
CH5 and CH6. When a “H” level
signal is applied to SWIN pin after releasing the UVLO
and the voltage at CIN6 pin rises above 0.9V(typical),
the IC pulls low the voltage at SWOUT pin, turning on
the external p-channel MOSFETs to generate output
voltages.
Application Information
Soft-Start Interval Settings
The CH6 soft-start time depends on the capacitor C
CIN6
and is determined as the following equation:
1
ln
=
(V)
1.26
(V)
V
)
(k
100
(k
62.5
(k
37.5
(F)
C
(S)
)
CIN6
CIN6
C
CIN6
CIN6
V
CIN6
VB(2V)
Error
Amp. 6
37.5k
62.5k
F)
(
C
0.07
(S)
ts
CIN6
μ
≈
The soft-start time until CH6 output voltage reaches
95% of the set voltage is determined as the following
equation:
On CH1 to CH5, the soft-start time depending on the
capacitor C
S
determined as the following equation :
Triangular Oscillator Frequency Setting
The triangular oscillator frequency set by the timing
capacitor (CT) connected to the CT pin and the timing
resistor (RT) connected to the RT pin determined as
the following equation:
(
C
1.25
(S)
OSC
ts
f
μ
≈
(pF)
CT
)
(k
OUTA4
(kHz)
≈
Output Voltage Settings
The output voltage is set by the external resistor-di-
vider connected with converter output, error amplifier
input, and ground.
(1) CH1 to CH3, CH5
IN1
V
O
Error
Amp. 1
1.25V
R1
R2
1
=
R2
R1
1.25V
(V)
Vo
(2)
CH4
R2
R1
1.25V
-
=
(V)
Vo
IN4
V
O
Error
Amp. 4
1.25V
R1
INV
Amp. 4
R3
INA4
(3) CH6
1
=
R2
R1
1.26V
(V)
Vo
CIN6
VB(2V)
Error
Amp. 6
37.5k
62.5k
IN6
V
O
R1
R2
Time Constant Setting for Timer-Latch Short-Cir-
cuit Protection Circuit
The time constant for timer-latch short-circuit protec-
tion is set by the capacitor C
SCP
and determined as
the following equation :
PE
=
F)
(
C
0.70
(S)
t
SCP
μ