TC1426_13 Datasheet, PDF (6/16 Pages) Microchip Technology – 1.2A Dual High-Speed MOSFET Drivers

TC1426/TC1427/TC1428
3.0 APPLICATIONS INFORMATION
3.1 SUPPLY BYPASSING
Large currents are required to charge and discharge
capacitive loads quickly. For example, charging a 1000
pF load to 16V in 25 nsec requires a 0.8A current from
the device's power supply.
To ensure low supply impedance over a wide frequency
range, a parallel capacitor combination is recom-
mended for supply bypassing. Low-inductance ceramic
MLC capacitors with short lead lengths (<0.5-in.)
should be used. A 1.0 F film capacitor in parallel with
one or two 0.1 F ceramic MLC capacitors normally
provides adequate bypassing.
3.2 GROUNDING
The TC1426 and TC1428 contain inverting drivers.
Individual ground returns for the input and output
circuits or a ground plane should be used. This will
reduce negative feedback that causes degradation in
switching speed characteristics.
Test Circuit
Input
V_DD = 16V
1 μF
WIMA
MKS-2
0.1 μF MLC
1
2
TC1426
(1/2 TC1428)
Output
C_L = 1000 pF
3.3 INPUT STAGE
The input voltage level changes the no-load or
quiescent supply current. The N-channel MOSFET
input stage transistor drives a 2.5 mA current source
load. With a logic ‘1’ input, the maximum quiescent
supply current is 9 mA. Logic ‘0’ input level signals
reduce quiescent current to 500 A maximum. Unused
driver inputs must be connected to V_DD or GND.
Minimum power dissipation occurs for logic ‘0’ inputs
for the TC1426/TC1427/TC1428.
The drivers are designed with 100 mV of hysteresis.
This provides clean transitions and minimizes output
stage current spiking when changing states. Input
voltage thresholds are approximately 1.5V, making a
logic ‘1’ input any voltage greater than 1.5V up to V_DD.
Input current is less than 1 A over this range.
The TC1426/TC1427/TC1428 may be directly driven
by the TL494, SG1526/27, TC38C42, TC170 and
similar switch-mode power supply integrated circuits.
Test Circuit
Input
V_DD = 16V
1 μF
WIMA
MKS-2
0.1 μF MLC
1
Output
C_L = 1000 pF
2
TC1427
(1/2 TC1428)
+5V
Input
0V
V_DD
Output
0V
10%
t_D1
t_F
90%
10%
90%
t_D2
t_R
90%
10%
FIGURE 3-1:
Time
Inverting Driver Switching
+5V
Input
0V
V_DD
Output
0V
10%
t_D1 ^90%
t_R
10%
90%
t_D2
90%
t_F
10%
FIGURE 3-2:
Switching Time
Noninverting Driver
DS21393D-page 6
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