HA17524P Datasheet, PDF (5/18 Pages) Hitachi Semiconductor – Switching Regulator Controller

HA17524P/FP
Q₁
6
I
R_T
V_REF
Q₂
Q₃
Discharge
7
I _CT
V_H
∆V
T
V_L
C_T Terminal Waveform
I ≈ ^{VREF – VEB (Q2) – VEB (Q3)}
R_T
∆V = V_H – V_L ≅ 3.8 – 0.9 = 2.9 V
1
T ≈ C_T · ∆V · _I
Figure 4 Oscillating Circuit and C_T Terminal Waveform
The oscillator output pulse signal is used as the flip flop clock pulse and as switching pulses for the output
transistors, synchronous to the clock pulse.
The pulse-widths which can be controlled by the timing capacitor C_T as shown in figure 5, increases output
dead time.
10
VCC = 20 V
R_T = 10 kΩ
Ta = 25°C
3
1.0
0.3
0.1
0.001 0.003
0.01
0.03
0.1
Timing Capacitance C_T (µF)
Figure 5 Dead Time vs Timing Capacitance
Reference Voltage: The built-in regulator (reference voltage: V_REF = 5 ±0.4 V) can be used as a reference
power supply for the error amplifier, which determines output voltage (V_OUT). It is also connected as a bias
source for another circuits in IC.
5