5 How to Make a TPHL Propagation Delay Measurement With Split Supplies
Note
Do not turn on power supply until all connections to the device are made to the board.
1. Short VEE_OUT jumper to SYS_GND.
2. Set one channel of the DC power supply to output a -2.5 V voltage and set its current limit to 100 mA. After
ensuring that this channel is disabled, connect VEE_IN to this supply.
3. Set one channel of the DC power supply to output a 2.5 V voltage and set its current limit to 100 mA. After
ensuring that this channel is disabled, connect VCC to this supply.
4. Ensure that cables connecting to IN+SENSE, OUT+, and OUT- are matched length and impedance. Perform
any deskewing if no matched cables are available. For this setup, IN- is a DC voltage reference so the
cables used for IN- and IN- SENSE do not need to be matched.
5. On the signal generator output, set the function generator to produce a square wave output with 100 mVpp
at 10-MHz, with a 0 V DC offset. This results in a 50 mV overdrive and 50 mV underdrive. Disable the signal
generator output. Connect the signal generator output to IN+.
6. Ground the inverting input, IN-, to ground to establish the threshold for the comparator at 0 V.
7. Connect OUTP and OUTN to a 50-Ω terminated channel on the oscilloscope.
Note
that with capacitors C10
and C11 populated, the discharging and charging of these output capacitors will cause the output to be
averaged.
8. Connect IN+SENSE, to another 50-Ω terminated scope channel.
9. Enable the VCC/VEE_IN power supply.
10. Verify the total supply current is < 30 mA.
11. Enable the signal generator.
12. Monitor and verify the inputs from IN+SENSE and IN- is 0 V DC.
13. Monitor and verify the outputs for OUT+ and OUT-.
SMA
High Speed Pulse Generator
(<500 ps Rise/Fall Time, 50 Ohm
Terminated)
V
EEOUT
= GND
(Via Jumper)
V
EEIN
= -2.5V
V
CC
= 2.5V
IN+
SENSE
OUT-
OUT+
IN-
IN+
IN-
SENSE
GND
High Speed Oscilloscope
(50 Ohm Terminations)
CH.4
CH.3
CH.1
Legend
Matched SMA cable length
Jumper
SMA cable
Figure 5-1. TLV3801 EVM Propagation Delay with Latch Setup
How to Make a TPHL Propagation Delay Measurement With Split Supplies
6
TLV3801EVM User’s Guide
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