參數(shù)資料
型號: L6743Q
廠商: 意法半導體
英文描述: High current MOSFET driver
中文描述: 高電流MOSFET驅動器
文件頁數(shù): 9/17頁
文件大?。?/td> 282K
代理商: L6743Q
L6743, L6743Q
Device description and operation
9/17
5.3
Internal BOOT diode
L6743, L6743Q embeds a boot diode to supply the High-Side driver saving the use of an
external component. Simply connecting an external capacitor between BOOT and PHASE
complete the High-Side supply connections.
To prevent bootstrap capacitor to extra-charge as a consequence of large negative spikes,
an external series resistance R
BOOT
(in the range of few ohms) may be required in series to
BOOT pin.
Bootstrap capacitor needs to be designed in order to show a negligible discharge due to the
High-Side MOSFET turn-on. In fact it must give a stable voltage supply to the High-Side
driver during the MOSFET turn-on also minimizing the power dissipated by the embedded
Boot Diode.
Figure 5
gives some guidelines on how to select the capacitance value for the
bootstrap according to the desired discharge and depending on the selected mosfet.
Figure 5.
Bootstrap capacitance design
5.4
Power dissipation
L6743, L6743Q embeds high current drivers for both High-Side and Low-Side MOSFETs: it
is then important to consider the power that the device is going to dissipate in driving them
in order to avoid overcoming the maximum junction operative temperature.
Two main terms contribute in the device power dissipation: bias power and drivers' power.
Device Power (P
DC
) depends on the static consumption of the device through the
supply pins and it is simply quantifiable as follow:
P
DC
V
CC
I
CC
V
PVCC
I
PVCC
+
=
Drivers' power is the power needed by the driver to continuously switch ON and OFF
the external MOSFETs; it is a function of the switching frequency and total gate charge
of the selected MOSFETs. It can be quantified considering that the total power P
SW
dissipated to switch the MOSFETs dissipated by three main factors: external gate
resistance (when present), intrinsic MOSFET resistance and intrinsic driver resistance.
This last term is the important one to be determined to calculate the device power
dissipation.
The total power dissipated to switch the mosfets results:
P
SW
F
SW
Q
GHS
PVCC
Q
GLS
VCC
+
(
)
=
0.0
0.5
1.0
1.5
2.0
2.5
0
10
20
30
40
50
60
70
80
90
100
High-Side MOSFET Gate Charge [nC]
B
Cboot = 47nF
Cboot = 100nF
Cboot = 220nF
Cboot = 330nF
Cboot = 470nF
0
500
1000
1500
2000
2500
0.0
0.2
0.4
0.6
0.8
1.0
Boot Cap Delta Voltage [V]
B
Qg = 10nC
Qg = 25nC
Qg = 50nC
Qg = 100nC
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相關代理商/技術參數(shù)
參數(shù)描述
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L6747C 制造商:STMicroelectronics 功能描述:MOSFET DRVR 3.5A 2-OUT Hi/Lo Side Inv/Non-Inv 8-Pin VFDFPN EP Tube 制造商:STMicroelectronics 功能描述:HANDHELD & COMPUTER PM - Rail/Tube 制造商:STMicroelectronics 功能描述:N-Ch FET PWM Driver Dual 5V to 12V HC