ADR425 equiv with sink capabilities.

[Fred Bartoli]

In a attempt to be clever I used this ref for making a floating negative
ref voltage, without checking further than some datasheet internal
drawing showing the output driver as an opamp.

Yes, I should have known better, but now I've something like:

.---------------.
V+ -----|Vcc Vout |--------.
| | |
| | ===
| | GND
| |
| |
| 0V |
'---------------'
|
|
+---------------> -Vref
|
.-.
| |
| |
'-'
|
V-


with a ref. that can't sink the output current, so it doesn't work.

Anyone knowing a pin compatible substitution for the ADR425 (5V-MSOP8)
able to sink current. This will avoid me a new PCB run.

 

[Jim Thompson]

In a attempt to be clever I used this ref for making a floating negative
ref voltage, without checking further than some datasheet internal
drawing showing the output driver as an opamp.

Yes, I should have known better, but now I've something like:

.---------------.
V+ -----|Vcc Vout |--------.
| | |
| | ===
| | GND
| |
| |
| 0V |
'---------------'
|
|
+---------------> -Vref
|
.-.
| |
| |
'-'
|
V-


with a ref. that can't sink the output current, so it doesn't work.

Anyone knowing a pin compatible substitution for the ADR425 (5V-MSOP8)
able to sink current. This will avoid me a new PCB run.

Similar to the data sheet Figure 47:


.---------------.
V+ -----|Vcc Vout |-----. .-------.
| | | | |
| | --------- ===
| | \ - + / GND
| | \ /
| | \ /
| 0V | \ /
'---------------' |
| |
| |
+---------------+-----> OUT

Of course it takes a really good OpAmp to maintain the accuracy :-(

...Jim Thompson

 

[Fred Bartoli]

Jim Thompson a écrit :

Similar to the data sheet Figure 47:


.---------------.
V+ -----|Vcc Vout |-----. .-------.
| | | | |
| | --------- ===
| | \ - + / GND
| | \ /
| | \ /
| 0V | \ /
'---------------' |
| |
| |
+---------------+-----> OUT

Of course it takes a really good OpAmp to maintain the accuracy :-(

Indeed, but I was trying to avoid that

 

[Tony Williams]

.---------------.
V+ -----|Vcc Vout |--------.
| | |
| | ===
| | GND
| |
| |
| 0V |
'---------------'
|
|
+---------------> -Vref
|
.-.
| |
| |
'-'
|
V-

Anyone knowing a pin compatible substitution for the ADR425
(5V-MSOP8) able to sink current. This will avoid me a new PCB
run.

Could you hack an ADR550 in there, as a two-terminal
shunt reference between GND and -Vref?