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HA16114 Ver la hoja de datos (PDF) - Renesas Electronics

Número de piezacomponentes Descripciónfabricante
HA16114 Switching Regulator for Chopper Type DC/DC Converter Renesas
Renesas Electronics Renesas
HA16114 Datasheet PDF : 34 Pages
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HA16116FP/FPJ, HA16121FP/FPJ
6.3 Calculating Intermittent Operation Timing
Intermittent operation timing is calculated as follows.
(1) TON time (the time until the IC is shut off when continuous overcurrent occurs)
TON = CON/OFF × RB × ln
3VBE
2VBE
×
1
1 On duty*
1
1
= CON/OFF × RB × ln1.5 × 1 On duty* 0.4 × CON/OFF × RB × 1 On duty*
(2) TOFF time (when the IC is off, the time until it next goes on)
TOFF = CON/OFF × (RA + RB) × ln
VIN 2VBE
VIN 3VBE
Where, VBE 0.7 V
Note: 1. On duty is the percent of time the IC is on during one PWM cycle when the pulse-by-pulse
current limiter is operating.
From the first equation (1) above, it is seen that the shorter the time TON when the pulse-by-pulse current
limiter goes into effect (resulting in a larger overload), the smaller the value TON becomes.
As seen in the second equation (2), TOFF is a function of VIN. Further, according to this setting, when VIN is
switched on, the IC goes on only after TOFF has elapsed.
Triangle wave
PWM output
(step-down channel)
tON
T
Dead band voltage
Point at which current
limiter operate
On duty = tON
T
Where T = 1/fOSC
Note: On duty is the percent of time the IC is on during one PWM cycle when
the pulse-by-pulse current limiter is operating.
Figure 6.3
Rev.2.0, Sep.18.2003, page 16 of 33
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