AN8014 Panasonic Semiconductor, AN8014 Datasheet - Page 11

• Manufacturer Part Number: AN8014
• Description: Step-down/ step-up/ or inverting DC-DC converter control IC
• Manufacturer: Panasonic Semiconductor

Voltage regulators
[1] Function descriptions (continued)
8. Overcurrent protection block
Application Notes (continued)
Overcurrent protection input (CLM)
(power MOSFET), the block regulates the upper limit of the current flowing in the main switch, thus protects the
parts such as main switch device, a flywheel diode and a choke coil from the damage caused by the overcurrent.
between the main switch device and V
95 mV", threshold level for overcurrent detection, the output drive transistor is cut off so that no more current
flows in the main switch device. This control is repeated at each cycle. When overcurrent is detected once, the
transistor remains off during the same cycle, and is switched on in the next cycle.
filter to eliminate noise due to parasitic capacitance when
the power MOSFET is turned on.
the following.
Triangular wave (CT)
Error amplifier output (FB)
Latch circuit set signal
Latch circuit reset signal
Output waveform (Out)
Utilizing that the overcurrent of power output is proportional to the current value which flows in the main switch
The current detection are done by monitoring, at CLM pin (pin 10), the voltage drop in resistor which is placed
When the main switch device (power MOSFET) is switched on and the voltage of CLM pin reaches "V
Such an overcurrent detection method is called "Pulse-by-pulse overcurrent detection."
R2 and C1 shown in figure 6 constitute a low-pass
The cut-off frequency of the filter is obtained from
f
C
2 C
(1) Overcurrent detection
Figure 5. Waveforms of the pulse-by-pulse overcurrent protection operation
1
1
R
2
[Hz]
(2) Latch set
(3) Output Off
(4) Latch reset
CC
pin.
(5) Turned on in the next cycle
In
Figure 6. CLM noise filter circuit
C1
R1
t
DLY
: Delay time
V-Out
R2
CLM
AN8014S
1.32 V
0.44 V
High
Low
V
V
High
Low
High
Low
CC
CC
95 mV
CC
Out
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