BS2114F Datasheet, PDF (13/23 Pages) Rohm – 600V High voltage High & Low-side, Gate Driver

BS2114F
(2) Bootstrap Capacitor CBS
To reduce ripple voltage, ceramic capacitors with low ESR value are recommended for use in the bootstrap circuit.
The maximum voltage drop (ΔVBS) that we have to guarantee when the high-side switch is in on state must be:
V_BS VCC VF V_GSMIN V_OL
(9)
where:
VCC is the gate driver supply voltage,
VF is the bootstrap diode forward voltage drop, and
VGSMIN is the minimum gate - source voltage,
VOL is the low-side switch drain - source voltage
The total charge supplied (QTotal) by the bootstrap capacitor should have a value near the following formulas.
Q_Total  Q_G  (I _LKGS  I _LK  I _LKDIO  I_QBS )  T_HON
(10)
where:
QG is the total gate charge,
ILKGS is the switch gate - source leakage current,
ILKDIO is the bootstrap diode leakage current,
ILK is the level shifter circuit leakage current,
IQBS is the quiescent current, and
THON is the high-side switch on time.
The bootstrap capacitor value should satisfy the following formula.
C_BS

Q_Total
V_BS
(11)
However, BS2114F has a BSTUVLO function to prevent malfunction at low voltage between VB and VS.
Please ensure sufficient capacitor margin to prevent BSTUVLO malfunction.
It is not able to keep turning-on the same way as the high side switch driver because of the specifications of the
bootstrap circuits.
In addition, it is recommended to insert a 1 μF ceramic capacitor between VB and VS. This capacitor should be placed as
close as possible to these pins for noise reduction.
VCC
VF
VB
VCC VS
COM
CBS
VGS
VOL
Figure 28. Bootstrap Power Supply Circuit
(3) Input Capacitor
Mount a low-ESR ceramic input capacitor near the VCC pin to reduce input ripple.
For BS2114F, it is recommended to use a capacitor value two times larger than that of the bootstrap capacitor or more.
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