Texas Instruments REF8EVM User Manual page 4

Hardware
2.2 EVM Connection
There are multiple options to power up REF8EVM. There are onboard LDOs provided or users can bypass the
LDOs to directly power REF80 with an external power supply. The TPS7A4901DRBR, a low noise LDO, and
LM317AEMP/NOPB, a high output current LDO, can be used if a low noise, regulated input voltage is desired
to further isolate the noise of REF80 from the noise generated by a bench power supply. These LDOs generate
voltages at about 15V. REF8EVM has been validated to meet REF80 specifications with both options. The input
voltage ranges of each device can be seen below in
Input Setting
VDD Bypass (J17)
Heater Vin Bypass (J20)
VDD LDO (J17)
Heater Vin LDO (J20)
Default EVM setup is shown in
ways. The output reference can be measured by connecting the VREF+ and VREF- directly to an 8.5 digit
multimeter, by installing user provided binding posts J14 and J16 where J14 is VREF+ and J16 is VREF-, or by
measuring the output voltage using SMA connector J4. For best temperature drift performance, use low thermal
EMF banana plugs to measure VREF+ and VREF- rather than SMA cables to avoid unwanted offsets due to
imbalanced thermal EMF effects.
VREF+ direct
connection to 3458A
DMM
VREF- direct
connection to 3458A
DMM
4 REF80 Evaluation Module
Table
Table 2-1. Input Voltage Ranges for REF8EVM Setup
Device
REF80000B1NAJT (VDD Pin)
REF80000B1NAJT
(HEATP Pin)
TPS7A4901DRBR
LM317AEMP/NOPB
Figure 2-2. The output reference voltage can also be measured in many different
Figure 2-2. REF8EVM Default Setup
Copyright © 2024 Texas Instruments Incorporated
2-1.
EVM Minimum Input Voltage
10V
10V
16V
18.5V
SNAU304A – AUGUST 2024 – REVISED OCTOBER 2024
www.ti.com
EVM Maximum Input Voltage
16.5V
42V
35V
37V
Heater GND
Heater VIN
VIN
GND
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