LM2904B-Q1: Output swing to rail spec in datasheet

Johnny Guo

Part Number: LM2904B-Q1
Other Parts Discussed in Thread: LM2904-Q1, LM2904

Hi team,

We are promoting LM2904B-Q1, and some questions about LM2904B-Q1 output swing from rail spec need to check with you.

1. In datasheet, LM2904B-Q1 output swing spec is shown below. For Vs=5V, Iout=1mA, TA=25C application, is the maximum output voltage (5V-1.4V)=3.6V typical?

Also in datasheet figure 11, the swing to rail voltage did not vary too much vs. temperature, like (5V-1.5V)=3.5V typical.

2. For LM2904-Q1 spec below, for Vs=5V, RL=10k, TA=25C application, is the maximum output voltage (5V-1.5V)=3.5V typical?

And considering -40C-125C range, the maximum output voltage should be (5V-3V)=2V typical?

Thanks.

Johnny

over 4 years ago

0 Tim Claycomb over 4 years ago

TI__Genius 15410 points

Hi Johnny,

1. Yes, the typical performance for output swing to the positive rail on a 5V supply with 1mA output will be 3.6V.

2. No, this is not the typical specification. This is a worst case specification which is why it is under the "Min" column.

The over temp specifications are for a maximum supply voltage. The specification listed is for the voltage from the rail not the maximum output voltage. For example, for a supply voltage of 26V the typical output voltage swing with RL>10kohm over temp will be 24V (26V - 2V). For more guidance on the LM2904 I recommend reading "Application Design Guide for LM324/LM358 Devices".

Thank you,

Tim Claycomb

0 Johnny Guo over 4 years ago in reply to Tim Claycomb

TI__Expert 4910 points

Hi Tim,

Thanks for reply. For LM2894B-Q1, what is the worst case of maximum output that we can achieve?

Customer's application: V+=5V, V-=0V, Iout=1mA, TA=-40~125C. Will 3.4V in below figure applied to all chips? Customer's design target is 3.5V under all condition, need to confirm with you.

Thanks.

Johnny

0 Tim Claycomb over 4 years ago in reply to Johnny Guo

TI__Genius 15410 points

Hi Johnny,

The LM2908B-Q1 does not have a min/max spec for output swing to the positive rail over temperature. Therefore, there is no worst case specification.

The maximum specification for 1mA output is 1.48V from the positive rail for the LM2904B-Q1, or 3.52V on a 5V supply. However, this is only at 25C and not over temperature. We will not provide a worst case number for this condition over temperature because there is not a specification for it in the datasheet.

Thank you,

Tim Claycomb

0 Johnny Guo over 4 years ago in reply to Tim Claycomb

TI__Expert 4910 points

Tim,

For the -40C/25C/125C curve in Figure 11, the worst case of Vout is 3.4V @-40C, 5V Vs, 1mA. Can we take this as the Vout capability?

Thanks.

Johnny

0 Tim Claycomb over 4 years ago in reply to Johnny Guo

TI__Genius 15410 points

Hi Johnny,

This graph is not worst case performance, this is typical performance.

Thank you,

Tim Claycomb

0 Johnny Guo over 4 years ago in reply to Tim Claycomb

TI__Expert 4910 points

Hi Tim,

So how can we tell customer what is the maximum output voltage they can achieve in design?

Below is LM2904-Q1 spec, can we take below data 5V-3V=2V as worst case?

0 Tim Claycomb over 4 years ago in reply to Johnny Guo

TI__Genius 15410 points

Hi Johnny,

A maximum output voltage cannot be provided over temperature at a 5V supply because there is not a min/max spec in the datasheet for that exact condition. I recommend using the "Application Design Guide for LM324/LM358 Devices", the min/max specs at 25C provided in the datasheet, and the output current vs. output voltage curves as guidance.

Thank you,

Tim Claycomb

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LM2904B-Q1: Output swing to rail spec in datasheet