LMV358: When the in-phase input is greater than 2.7V, an anomaly occurs

Timsen

Part Number: LMV358
Other Parts Discussed in Thread: , TLV2314, TLV9002

Dear all：

Our company USES TI LMV358 to form a voltage follower circuit (see attachment), and USES 3.3V for power supply. When the input of 0-3V varies linearly at the same phase end, the output follows 0-3V.

The test results are as follows:
When the in-phase input is less than 2.7V, the voltage follows well. When the in-phase input is more than 2.7V, the abnormal results are as follows:
1. The output terminal voltage jumps to 3.276V (same as the measured supply voltage 3.276V)
2. The output terminal voltage is fixed at 2.726v (the actual supply voltage is 3.276V)

When the output is abnormal, the input terminal voltage still changes linearly accurately, so the LMV358 output is abnormal.

May I ask the following questions: 1. What is the input voltage range of LMV358?Whether input above 2.7v in the same phase will cause it to exceed the linear workspace

2. What is the output voltage of LMV358 beyond the linear working area?

3. What is the input range (curve) of different supply voltage?

over 4 years ago

0 Bala Ravi over 4 years ago

TI__Expert 6625 points

Hi Timsen,

Your circuit is violating the input common mode range. When this happens the inputs can get cut off. There is an upgraded version of this device, where this does not happen. Please check out LMV358A. Here is the link to the product folder for PSPICE models: http://www.ti.com/product/LMV358A/toolssoftware.

Best Regards,

Bala Ravi

0 Timsen over 4 years ago in reply to Bala Ravi

Expert 1660 points

Hi Bala：

Thank you for your reply！

My circuit is violating the input common mode range?And What is the common mode input range of LMV358?

what about common mode input range of LMV358A?

Thank you!

0 Michael Steffes over 4 years ago in reply to Timsen

Guru 47485 points

So this input range thing is always a headroom to the supplies, sometimes shown that way, sometimes not - the original LMV358 shows the old way where the input can get to within 1V of the positive supply,

The LMV358A is actually no better, showing it as a headroom spec of 1V to the positive supply - if you need a unity gain buffer with swing to +Vcc, there are lots of RRIO parts out there these days.

This comes up so often, I made it Insight #1 in this monthly series I am writing for Planet Analog, Working on #12 right now, "Why is Gain Bandwidth Product so confusing"

https://www.planetanalog.com/author.asp?section_id=3404&doc_id=564967

0 Ron Michallick over 4 years ago in reply to Timsen

TI__Guru*** 139956 points

Timsen,

LMV358A is not optimized for best performance above Vs-1V, however there will be no phase reversal for input up to Vs which is far better then LMV358.

0 Michael Steffes over 4 years ago in reply to Ron Michallick

Guru 47485 points

This might be the only part in the industry claiming RR input with a 1V headroom worst cast to the positive supply? The typical of 0.1V headroom looks RRinput but he have to design for worst case.

The cross reference tool points me to the TLV2314 as maybe a better choice? But, that overtemp CMRR spec is a bit of a red flag -

0 Michael Steffes over 4 years ago in reply to Michael Steffes

Guru 47485 points

A closer choice might be the TLV9002, but it has that same over temp caveat - basically saying to stay out of the crossover region if you want good CMRR. so if you do go into that region to get better unity gain buffer I/O swing close to +Vcc, you will be getting a offset voltage shift and then more gain error due to lower CMRR I am guessing,

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LMV358: When the in-phase input is greater than 2.7V, an anomaly occurs