HA17384SPS Datasheet, PDF (18/29 Pages) Hitachi Semiconductor – High Speed Current Mode PWM Control IC for Switching Power Supply

HA17384SPS/SRP, HA17384HPS/HRP, HA17385HPS/HRP
500
Ta = 25°C
V_IN = 15V
200
C
100
50
20
0.047_µ^0F.022_µ^{0.F014µ7F0202p0F01p0F00pTF= 470pF}
10
5
500 1k
2k 5k 10k 20k 50k 100k 200k
Timing resistance R_T (Ω)
Figure 7 scillation Frequency vs. Timing Resistance
Case 1.
Setting large maximum duty cycle.
Triangular wave
PWM maximum ON pulse
Case 2.
Setting small maximum duty cycle.
Du max = 95%
fosc = 52kHz
In the case of small C_T and large R_T
(ex. C_T = 3300pF, R_T = 10kΩ)
Triangular wave
PWM maximum ON pulse
Du max = 40%
fosc = 52kHz
In the case of large C_T and small R_T
(ex. C_T = 0.033µF, R_T = 680Ω)
Figure 8 Relationship Between Triangular Wave and Maximum ON Duty of PWM Pulse
Rev.3.00 Jun 15, 2005 page 18 of 28