The 8 and 16-pin versions of the LT1072 have the emitters
of the power transistor brought out separately from the
ground pin. This eliminates errors due to ground pin
voltage drops and allows the user to reduce switch current
limit 2:1 by leaving the second emitter (E2) disconnected.
The first emitter (E1) should always be connected to the
ground pin. Note that switch “on” resistance doubles
when E2 is left open, so efficiency will suffer somewhat
when switch currents exceed 100mA. Also, note that chip
dissipation will actually increase with E2 open during
normal load operation, even though dissipation in current
limit mode will decrease. See “Thermal Considerations.”