Lm317 as constant current source <10ma, what wrong happens

[Kokoriantz]

The LM317 is given in DS >10ma for voltage regulation. If used as current source <10ma with TO92 version, what can go wrong?
I tried out with 12v 7ma it worked perfectly with output ground to 8v.

[Kokoriantz]

The LM317L from ST datasheet gives the following minimum operating current graph as voltage regulator, but what happens in current source?

[timenutgoblin]

According to the Texas Instruments datasheet, the minimum load current is:
>=3.5mA and =<5mA for V_IN - V_OUT =< 40V.

Otherwise, it's:
>=1.5mA and =<2.5mA for V_IN - V_OUT is >= 3V and =<15V.

The minimum load current is required to maintain regulation. The values probably vary from device to device.

7mA is more than the minimum load current requirement. 

See attachment below.

[magic]

The minimum load current is required to maintain regulation.

This.

If you try to "force" the chip to conduct less current, you may find that 1.24V across ADJ-OUT is not enough to stop it from conducting. Maybe 1.5V will be enough to throttle it down to 1.25mA and 2V for 1mA, maybe 20V will make it 0.75mA, maybe even 40V won't be enough for 0.5mA. (Numbers are made up.)

What you will find is that it basically no longer works the way you want. You can just try it, I guess.

[timenutgoblin]

The LM317 is given in DS >10ma for voltage regulation. If used as current source <10ma with TO92 version, what can go wrong?
I tried out with 12v 7ma it worked perfectly with output ground to 8v.

The LM317L (TO-92) is the low-power variant of the LM317 (TO-220).

For the LM317, the Texas Instruments datasheet gives the minimum load current:
>=3.5mA and =<10mA for V_IN - V_OUT = 40V.

See attachment for LM317 below. Also a functional block diagram.

[Kokoriantz]

Thanks for the explanations. The two terminal current source needs a minimum current to establish the constant 1.2v. Then, if the current is less, it will not remain constant. I always read, never use LM317 less than 10ma as current source, when the 317L can be used instead of LM334, which needs some components to be temperature independent and it is much cheaper.