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HA16114 View Datasheet(PDF) - Renesas Electronics

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HA16114 Datasheet PDF : 34 Pages
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HA16116FP/FPJ, HA16121FP/FPJ
To Vref
VTH
VE/O
VDB
CT
PWM
comparator VIN
VTL
VDB R1 E/O
+
DB
+
5k
Booster
channel
On
tOFF tON
Off
PWM
CST R2
From UVL 0.8V
pulse
output Step-down/
inverting
Off
channel
On
T
1.6 V typ
1.0 V typ
VIN
GND
VIN
GND
Figure 3.1 Dead Band Duty Setting
3.2 Soft Start (SST) Setting (each channel)
When the power is turned on, the soft start function gradually raises VDB (refer to section 3.1), and the
PWM output pulse width gradually widens. This function is realized by adding a capacitor CST to the DB
pin. The function is realized as follows.
In the figure 3.2, the DB pin is clamped internally at approximately 0.8 V, which is 0.2 V lower than the
triangle wave VTL = 1.0 V typ.
tA: Standby time until PWM pulse starts widening.
tB: Time during which SST is in effect.
During soft start, the DB pin voltage in the figure below is as expressed in the following equation.
t t0.8
VSST = VDB 1 e T , tSST = tA + tB
Here,
t0.8 = T ln
1 0.8
VDB
,
T = CST (R1 // R2)
How to select values: If the soft start time tSST is too short, the DC/DC converter output voltage will tend to
overshoot. To prevent this, set tSST to a few tens of ms or above.
Rev.2.0, Sep.18.2003, page 11 of 33
 

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