Other Parts Discussed in Thread: LMV431, , LM431
I am doing a bench test comparison of the TLVH431CLPR versus LMV431 voltage shunt devices.
The component test using the circuit below resulted in Vref = 1.24v and Vout = 2.5v as expected. So, I am comfortable both the TLVH431 and LMV431 components are working well.
|
|
Vref |
Vout |
Iref_pin |
|
TLVH431CLPR |
1.24 |
2.5 |
536 uA |
|
LMV431 |
1.24 |
2.5 |
535 uA |
Next, I did a bench test with the following circuit. Note the LED will be eventually replaced with an opto-isolator.
The results are shown in the table below.
|
|
Vref |
Vout |
Iref_pin |
|
TLVH431CLPR |
0.9 |
1.7 |
708 uA |
|
LMV431 |
2.45 |
1.53 |
62 uA |
I expected Vref to be about 2.5v for both devices due to the R11 & R22 voltage divider (assuming negligible Iref_pin current) but the TLVH431 has dropped to Vref=0.9v. Note, the Iref_pin is drawing 708 uA for the TLVH431 but only 62 uA for the LMV431.
So, why is the TLVH431 drawing so much Iref_pin current?
