ICL7667 Datasheet, PDF (6/8 Pages) Intersil Corporation – Dual Power MOSFET Driver

ICL7667
18
16
14
12
10
8
6
4
2
0
-2
0
I_D = 1A
V_DD = 50V
680pF
V_DD = 375V
212pF
V_DD = 200V
630pF
2 4 6 8 10 12 14 16 18 20
GATE CHARGE - Q_G (NANO-COULOMBS)
FIGURE 9. MOSFET GATE DYNAMIC CHARACTERISTICS
Direct Drive of MOSFETs
Figure 11 shows interfaces between the ICL7667 and typical
switching regulator ICs. Note that unlike the DS0026, the
ICL7667 does not need a dropping resistor and speedup
capacitor between it and the regulator IC. The ICL7667, with
its high slew rate and high voltage drive can directly drive the
gate of the MOSFET. The SG1527 IC is the same as the
SG1525 IC, except that the outputs are inverted. This
inversion is needed since ICL7667 is an inverting buffer.
Transformer Coupled Drive of MOSFETs
Transformers are often used for isolation between the logic
and control section and the power section of a switching
regulator. The high output drive capability of the ICL7667
enables it to directly drive such transformers. Figure 11
shows a typical transformer coupled drive circuit. PWM ICs
with either active high or active low output can be used in
this circuit, since any inversion required can be obtained by
reversing the windings on the secondaries.
Buffered Drivers for Multiple MOSFETs
In very high power applications which use a group of
MOSFETs in parallel, the input capacitance may be very large
and it can be difficult to charge and discharge quickly. Figure
13 shows a circuit which works very well with very large
capacitance loads. When the input of the driver is zero, Q₁ is
held in conduction by the lower half of the ICL7667 and Q₂ is
clamped off by Q₁. When the input goes positive, Q₁ is turned
off and a current pulse is applied to the gate of Q₂ by the
upper half of the ICL7667 through the transformer, T₁. After
about 20ns, T₁ saturates and Q₂ is held on by its own C_GS
and the bootstrap circuit of C₁, D₁ and R₁. This bootstrap
circuit may not be needed at frequencies greater than 10kHz
since the input capacitance of Q₂ discharges slowly.
15V
+165V_DC
+V_C
A
+V
IRF730
SG1527
B
GND
ICL7667
-V
IRF730
15V
+V_C
C1
E1
TL494
C2
E2
GND
+15V
FIGURE 10A.
1K
+V
+165V_DC
IRF730
ICL7667
1K
-V
IRF730
FIGURE 10B.
FIGURE 10. DIRECT DRIVE OF MOSFET GATES
3-78
V_OUT