E7802 SEMTECH [Semtech Corporation], E7802 Datasheet - Page 7

• Manufacturer Part Number: E7802
• Description: Low Cost, Dual-Channel, 15V Pin Electronics Driver/Window Comparator
• Manufacturer: SEMTECH [Semtech Corporation]

Power Supply Decoupling
VCC, VEE, and DVEE should be decoupled to GND with a .1
µF chip capacitor in parallel with a .00 µF chip capacitor
for best AC performance. A VCC, VEE, and DVEE plane, or
at least a solid power bus, is recommended for optimal
performance.
VH and VL Inputs
As the VH and VL inputs are unbuffered to the driver and
need to supply the output current which can be quite large
during edge transitions, bypass capacitors for these inputs
are needed to supply the transient currents in proportion
to the output current requirements (See Applications Note
PE-A1).
For applications where VH and VL are shared over multiple
channels, a solid power plane to distribute these levels with
local bypassing is recommended for best AC performance
.
Power Supply Sequencing/Latch-Up Protection
In order to avoid the possibility of latch-up when powering
this device up (or down), be careful that the conditions
listed in the Absolute Maximum Ratings are never violated.
The power supplies should never be in reverse-polarity with
respect to ground, and the input signals should never go
beyond the power supply rails.
Furthermore, the lower-voltage supplies should never be
greater than the higher-voltage supplies. This can easily
be implemented by utilizing the diode circuit depicted in
Figure 3 for each PCB utilizing the E7802. The following
conditions must be met at all times during power-up and
power-down:
The following sequencing can be used as a guideline when
powering up:
TEST AND MEASUREMENT PRODUCTS
Application Information
©
2008 Semtech Corp. , Rev. 5, 3/7/08
1.
2.
3.
1.
2.
3.
4.
5.
VEE <= DVEE <= VDD <= VCC
VEE <= Analog Inputs <= VCC
GND <= Digital Inputs <= VDD
VEE(substrate)
VCC
VDD
Digital Iputs
Analog Inputs
The three diode configuration shown in Figure 3 should be
used on a once-per-boad basis to help ensure that proper
supply polarities are maintained.
Warning: It is extremely important that the voltage on any
device pin does not exceed the range of VEE -0.5V or VCC
+0.5V at any time, either during power up, normal operation, or
during power down. Failure to adhere to this requirement could
result in latch-up of the device which could be destructive if the
system’s power supplies are capable of supplying large amounts
of current. Even if the device is not immediately destroyed, the
cumulative damage caused by the stress of repeated latchup
may affect device reliability.
Computing Maximum Power Comsumption
The power consumption of the E7802 increases with
increasing frequency and output voltage swing. The
diagram below shows the power consumption of the E7802
at a couple of different voltage swings across the frequency
range with both channels toggling.
7
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Figure 3. Power Supply Protection Scheme
0
E7802 Power Dissipation vs. Frequency
10
VCC
VDD
GND
VEE
(Open Transmission Line)
VCC=5.4V, VEE=-5V, DVEE=-3.6V, VDD=3.3V, 3V Swing
Toggle Freq (MHz)
VCC=15V, VEE=-5V, DVEE=0V, VDD=3.3V, 3V Swing
20
30
Diodes
1N5820 or
Equivalent
Schottky
www.semtech.com
40
E7802
50