HA16116FP Datasheet, PDF (20/34 Pages) Hitachi Semiconductor – Switching Regulator for Chopper Type DC/DC Converter

HA16116FP/FPJ, HA16121FP/FPJ
Overcurrent Detection Value Setting
The overcurrent detection value V_TH for this IC series is 0.2 V (Typ) and the bias current is 200 µA (Typ)
The power MOS FET peak current value before the current limiter goes into operation is derived from the
following equation.
I_D =
V_TCL − (R_F + R_CS) ⋅ I_BCL
R_CS
Here V_TH = V_IN – V_CL = 0.2 V, V_CL is a voltage referd on GND.
Note that C_F and R_CS form a low-pass filter, determined by their time constants, that prevents malfunctions
from current spikes when the power MOS FET is turned on or off.
S.V_IN
To other
circuitry
1k
200 A
C_F 1800 PF
V_CL
I _BCL
CL
R_F
240 Ω
R_CS
0.05 Ω
OUT
Detection
output
(internal)
−+
IN(—)
G
S
D
+
−
V_IN
This circuit is an example
for step-down output use.
V_O
Figure 8.1 Example for Step-Down Use
The sample values given in this figure are calculated from the following equation.
I_D
=
0.2
V
−
(240
Ω + 0.05
0.05 Ω
Ω)
×
200
µA
= 3.04 [A]
The filter cutoff frequency is calculated as follows.
1
1
f_C =
2π C_F R_F
=
6.28 × 1800 pF × 240 Ω
= 370 [kHz]
20