TC1426 Datasheet, PDF (6/14 Pages) TelCom Semiconductor, Inc – 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
1000pF load to 16V in 25nsec requires a 0.8A current
from the device’s power supply.
To guarantee low supply impedance over a wide
frequency range, a parallel capacitor combination is
recommended for supply bypassing. Low-inductance
ceramic MLC capacitors with short lead lengths
(<0.5-in.) should be used. A 1.0µF film capacitor in
parallel with one or two 0.1µF 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.
FIGURE 3-1:
Test Circuit
INVERTING DRIVER
SWITCHING TIME
V_DD = 16V
1µF
MKS-2
0.1µF MLC
Input
1
2
Output
C_L = 1000pF
TC1426
(1/2 TC1428)
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 2.5mA current source
load. With a logic "1" input, the maximum quiescent
supply current is 9mA. Logic "0" input level signals
reduce quiescent current to 500µA 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 100mV 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 1µA 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.
FIGURE 3-2:
Test Circuit
Input
NONINVERTING DRIVER
SWITCHING TIME
V_DD = 16V
1µF
WIMA
MKS-2
0.1µF MLC
1
Output
C_L = 1000pF
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%
+5V
Input
0V
V_DD
Output
0V
10%
t_D1 ^90%
t_R
10%
90%
t_D2
90%
t_F
10%
DS21393B-page 6
 2002 Microchip Technology Inc.