HA16120FP HITACHI [Hitachi Semiconductor], HA16120FP Datasheet - Page 17

• Manufacturer Part Number: HA16120FP
• Description: Switching Regulator for Chopper Type DC/DC Converter
• Manufacturer: HITACHI [Hitachi Semiconductor]

7.2 Intermittent Mode Timing Diagram (V
7.3 Calculation of Intermittent Mode Timing
Intermittent mode timing is calculated as follows.
(1) T
(2) T
The greater the overload, the sooner the pulse-by-pulse current limiter operates, the smaller t
and from the first equation (1) above, the smaller T
depends on V
not turn on until T
ON
OFF
(time until the IC shuts off when continuous overcurrent occurs)
(time from when the IC shuts off until it next turns on)
T
T
Where V
ON
OFF
IN
Sawtooth wave
Note: On duty is the percent of time the IC output is on during one PWM cycle
. Note that with the connections shown in the diagram, when V
Note: 1.
For details, see the overall waveform timing diagram.
= C
= C
= C
0.69
OFF
PWM output
(In case of HA16114)
ON/OFF
ON/OFF
when the pulse-by-pulse current limiter is operating.
ON/OFF
BE
Figure 7.2 Intermittent Mode Timing Diagram (V
has elapsed.
V
(See the figure 6.1.)
V
a.
b.
c.
C
BE
ON/OFF
0.7 V
ON/OFF
is the base-emitter voltage of internal transistors, and is approximately 0.7 V.
Continuous overcurrent is detected
Intermittent operation starts (IC is off)
Voltage if overcurrent ends (thick dotted line)
R
R
(R
B
B
A
+ R
ln
3V
2V
ln2
V
0 V
R
BE
BE
BE
B
B
*1
)
2V
V
BE
BE
ln
1
1
IC is on
On duty*
V
ON/OFF
V
On duty*
IN
1
HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
IN
2T
Figure 7.3
1
a
ON
1
2V
t
V
only)
ON
BE
c
BE
On duty*
O N
IC is off
T
1
T
b
ON
becomes. From the second equation (2), T
c
Dead-band voltage
On
On duty =
Where T = t/f
T
Point at which the current
limiter operates
Off
OFF
ON/OFF
t
ON
T
OSC
IN
On
only)
is switched on the IC does
100 (%)
t
ON
becomes,
OFF
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