Low Power 32kHz Circuit for Analog Quartz Watches - Ultra-Low Power
The EM1537 is an integrated circuit in a low power CMOS technology for battery operated wristwatches with bipolar stepping motors. Time base is a 32 kHz crystal oscillator. It has a very low current consumption of typ. 100 nA in a wide voltage range of 1.2 to 3.6 Volt.
The IC is available in two voltage ranges - 1.2 to 1.8 Volt and 1.8 to 3.6 V.
Motor pulse width is programmable from 0.098 ms to 14.65 ms in steps of 0.98 ms by metal mask. Motor period is programmable from 2 x 1s to 2 x 60 s in steps of 1 s selectable by metal mask. Motor pulse chopping is programmable from 1/8 to 8/8 in steps of 1/8 with chopping frequencies of 1024 Hz or 2048 Hz selectable by metal mask. Motor period in Motor test mode is selectable 2 x 31.25 ms or 2 x 62.5 ms by metal mask.
Input and output capacitors are integrated on chip and also programmable by metal mask.
With a fully debounced RESET pad, the motor can be stopped.
A multi-functional bi-directional pad MTEST acts as output for a 32 Hz or 512 Hz for frequency tuning - if open, or – if connected to Vp – accelerates the motor period by a factor of 16 or 32.