
MB39A104
■ABOUT TIMER-LATCH PROTECTION CIRCUIT
1. Setting
The overcurrent protection circuit is actuated upon completion of the
The internal current (ILIM) can be set by the timing resistor (RT) connected to the RT terminal (pin 12).
Time until activating timer circuit and setting latch is equal to
Internal current value: ILIM
ILIM (∝A) =: | 2700 |
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| RT (kΩ) |
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Detection current value: IOCP |
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IOCP (A) =: | ILIM(A) ⋅ RLIM(Ω) | − |
| (VIN(V) − VO(V)) ⋅ VO(V) | ||
| RON (Ω) | 2 | ⋅ VIN(V) ⋅ fOSC(Hz) ⋅ L(H) | |||
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RLIM : Overcurrent detection resistor
RON : External FET ON resistor
VIN : Input voltage
VO : DC/DC converter output voltage
fOSC : Oscillation frequency
L : Coil inductance
To reset the actuated protection circuit, either the power supply turn off and on again or set the CTL terminal (pin 24) to the "L" level to lower the VREF terminal (pin 17) voltage to 2.4 V (Min) or less.
• Overcurrent detection circuit
VIN
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| Current |
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| Protection |
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| Logic |
(1 ∝A) |
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CSCP |
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8 |
| VREF |
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S | R |
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Latch | UVLO |
− +
Each
Channel
Drive
Q1 L
(VS2)
21VS1
4
VO
(ILIM2)
20ILIM1 5 (RLIM)
17