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TLVH431: Comparison of TLVH431 vs. LMV431

Part Number: TLVH431
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=0.9vNote, 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?