SRP Hitachi Semiconductor, SRP Datasheet - Page 28

• Manufacturer Part Number: SRP
• Description: High Speed Current Mode PWM Control IC for Switching Power Supply
• Manufacturer: Hitachi Semiconductor

HA17384SPS/SRP, HA17384HPS/HRP, HA17385HPS/HRP
Notice for Use
1. OVP Latch Block
When configuring an IC power supply with an activation resistance and backup winding, such as an
AC/DC converter, the rise of V
occurring, but careful attention must be paid to high-frequency noise.
Also, this phenomenon is not occuring to the HA17384S, because OVP function is not built-in.
28
Case
When DC power is applied directly as the power supply of the HA17384H, HA17385H, without using
the transformer backup coil. Also, when high-frequency noise is superimposed on the V
Problem
The IC may not be turn on in the case of a circuit in which V
such as that shown in figure 16. Also, the OVP latch may operate even though the FB pin is normally at
V
Reason
Because of the IC circuit configuration, the timer latch block operates first.
Remedy (counter measure)
Take remedial action such as configuring a time constant circuit (R
the V
noise cancellation capacitor (C
ceramic capacitor) should be inserted between the V
OVP
or below after the IC is activated.
IN
rise speed below 10 V/100 s. Also, if there is marked high-frequency noise on the V
Figure 16 Example of Circuit with Fast V
Input
V
IN
IN
will normally be around 1 V/100 s, and there is no risk of this problem
N
) with the best possible high-frequency characteristics (such as a
GND
HA17384
Series
V
IN
IN
pin and GND, and close to the V
IN
rises quickly (10 V/100 s or faster),
Feedback
IN
B
, C
Rise Time
B
Output
) as shown in figure 17, to keep
IN
IN
pin.
pin.
IN
pin, a