LA5677M 查看數據表（PDF） - SANYO -> Panasonic
零件编号
产品描述 (功能)
比赛名单
LA5677M Datasheet PDF : 7 Pages
| |||
Equivalent Circuit Block Diagram
LA5677M
Operation Overview
1. Reference Voltage Block
The reference voltage block uses a 2.5 V reference voltage. This voltage is made available to external circuits from
pin 16, and at the same time is used as the reference power supply by internal circuits.
2. Low Input Malfunction Prevention Circuit Block
The low input malfunction prevention circuit prevents incorrect operation when the power supply is brought up or
during brief voltage drops. After power is applied and the reference voltage reaches Vbe, the output transistors are
held off until the power supply voltage becomes 2.72 V (typical). The dead time control pin voltage is held at the
high level (Vref) and the short circuit protection pin is held low (the initial state). Since this circuit has a hysteresis of
120 mV (typical) chattering due to power supply ripple can be prevented to a certain extent.
3. Timer-Latch Short Circuit Protection Circuit
During output overload, the timer-latch short circuit protection circuit’s short circuit protection comparator turns off
Q86 when the error amplifier inputs a low level signal (a voltage less than Vref/2) to one or both of the short circuit
protection comparator’s two non-inverting inputs. At this time the pin 15 voltage increases from about 0.75 V (steady
state) towards Vref as the external capacitor is charged from Vref through resistor R41 (80 kΩ). When the capacitor is
charged to about 1.2 V, the protection latch is set, the output transistors are turned off, and the idle time becomes 100%.
This also turns on Q97 which resets the protection enable state. The latch circuit reset voltage is under 1.9 V (typical).
VPE1 = Vref {1 – exp (–t1/R41•CPT)}
VPE2 = Vref {1 – exp (–t2/R41•CPT)}
0.75 = 2.5 {1 – exp (–t1/80 k•CPT)}
1.20 = 2.5 {1 – exp (–t2/80 k•CPT)}
t1 = 28.56 k•CPT
t2 = 52.31 k•CPT
tPT = t2 – t1 = 23.75 k•CPT
CPT = 42.1 × tPT [µF]
No. 3660-4/7
Share Link: 