HPW7095 Datasheet, PDF (16/23 Pages) List of Unclassifed Manufacturers – 6-Channel DC/DC Converter Control IC

HPW7095/A
Function Descriptions (Cont.)
Timer-latch short-circuit protection circuit
The short-circuit protection comparator in each chan-
nel (CH1 to CH5) monitors converter’s output voltage
via input pin of error amplifier. In CH6, the short-circuit
comparator detects the voltage at output of error
amplifier. As any detected voltages of CH1 to CH5
falls below 1.0V or the detected voltage of CH6 is larger
than 0.9V, the timer circuits is actuated to start charg-
ing the external capacitor CSCP connected from CSCP
pin to ground. When the rising voltage of CSCP reaches
0.7V, the IC turns off all external MOSFETs and pulls
up the voltage at SWOUT pin. Then the IC is latched.
Applying a signal from “L” to “H” to CTL pin enables
operation again. The short-circuit detection function
remains working during soft start operation on CH1 to
CH5.
rising voltage at CIN6 reaches 0.9V, the reference volt-
age starts to regulate and the internal source current
starts to charge the CS , starting a soft-start operation
on CH1 to CH5. During soft-start interval, the error
amplifiers compares the CH1 to CH5 output voltage to
the voltage at the CS pin. When any control pins (CH1,
2 to CH5) go “H” from “L” during the soft-start interval
(CH1 to CH5), the output rises rapidly to follow the
rising voltage at CS pin.
Input
CTL
CTL1,2
CTL3
CTL4
CTL5
Output
2V
VB
CIN6
CH6 Output
Voltage (Vo6)
VREF
0.9V
2.49V
Under-Voltage Lockout (UVLO) Circuit
The under-voltage lockout circuit monitors the supply
voltage at VCC pin to prevent wrong logic control. The
IC starts operation after the supply voltage rises above
it’s rising threshold. As the supply voltage falls below
it’s falling threshold, the IC turns off the external
MOSFETs and pulls up the voltage at SWOUT pin.
Soft-Start Operation
The soft-start function controls the output voltage rate
of rise to limit the current surge at start-up. For CH1
to CH5, the soft-start interval is programmed by the
soft-start capacitor, CS connected from CS pin to
ground and charged by an internal 1µA current source.
For CH6, a soucing current from the internal resistor-
divider charges the capacitor, CCIN6 connected from
CIN6 pin to ground, providing soft-start control.
Figure 1 and 2 show the soft-start processes. In figure
1, when all control pins (CTL, CTL1,2 to CTL 5) are
driven high (“H” level) at the same time, the voltage at
CIN6 pin starts to rise up by charging the capacitor
CCIN6 , starting a soft-start operation on CH6. After the
1.25V
CS
CH1 to CH5
O utputV oltages
(Vo1 to Vo5)
t
(1)
(1) to (2)
(3)
(3) to (4)
(3) (2)
(4)
: CH6 Soft-Start Interval
: VREF Output start
: CH1 to CH5 Soft-Start Interval
Figure 1 Soft-start waveforms
Input
CTL
CTL1,2
CTL3
CTL4
CTL5
Output
2V
VB
CIN6
CH6 Output
Voltage (Vo6)
VREF
0.9V
2.49V
1.25V
1.25V
CS
CH1 to CH3
O utputVoltages
(Vo1 to Vo3)
CH4 to CH5
O utputVoltages
(Vo4 to Vo5)
(1)
(3) (2) (4)
(5) (6)
t
(7)
(6)' (7)'
(1) to (2) : CH6 soft-start interval
(3)
: VREF Output start
(4) to (5) : CH1 to CH3 soft-start Interval
(6) to (7) : CH4, CH5 soft-start Interval
(6)' to (7)' : CH4(CH5) soft start interval as CTL4 (CTL5) go
"H" from "L" during CH1 to CH3 soft start interval
Figure 2 Soft-start waveforms
 Copyright HIPAC Semiconductor, Inc.
16
Rev. A.2 - July., 2004
www.hipacsemi.com