ISL21400 pdf datasheet (Progra

The ISL21400 features a precision voltage reference
combined with a temperature sensor whose output voltage
varies linearly with temperature. The precision 1.20V
reference has a very low temperature coefficient (tempco),
and its output voltage is scaled by an internal DAC (VREF) to
produce a temperature stable output voltage that is
programmable from 0V to 1.20V. The output voltage from the
temperature sensor (VTS) is summed with VREF to produce
a temperature dependent output voltage.
The slope of the VTS portion of the output voltage can be
programmed to be positive or negative in the range
-2.1mV/°C to +2.1mV/°C. A programmable gain amplifier
(PGA) sums the VTS and the VREF voltages and provides
gains of 1x, 2x, and 4x to scale the output up to 4.8V and the
slope to ±8.4mV/°C.
The VREF and VTS terms are programmable with 8 bits of
resolution via an I2C bus and the values are stored in
non-volatile registers. The PGA gain is also set via the I2C
bus and the value is stored in a non-volatile register.
Non-volatile memory storage assures the programmed
settings are retained on power-down, eliminating the need
for software initialization at device power-up.