An integrated voltage regulator provides the oscillator
www.dawtaitshheaet4wu.eclolmcontrolled negative supply voltage VREG.
This improves the stability of the oscillator and keeps cur-
rent consumption at a minimum.
An oscillator inverter with feedback resistor is provided
for generation of the 32768 Hz clock frequency. A total
capacitance of 24 pF is integrated.This can be selected for
COSCOUT in 2 pF increments via a mask option.
A 21-bit binary counter is provided, dividing the oscilla-
tor frequency down to 1/64 Hz. The leading six stages are
connected to VDD and VREG, while the remaining
15 stages are connected to VDD and VSS.
Motor Drive Output
The e1217X contains two push-pull output buffers for
driving bipolar stepping motors. During a motor pulse,
the n-channel device of one buffer and the p-channel de-
vice of the other buffer are activated. The p-channel
devices of both buffers are active (figure 3) between two
Cycle time and pulse width can be chosen via a metal-
mask option (table1).
A debounced RESET input is provided. Connecting the
RESET input to VDD resets the low order 12 stages of the
frequency divider, thus disabling further motor pulses.
Motor pulses in progress when the reset function is ap-
plied are completed. After releasing the RESET pad from
VDD, the next motor pulse appears with a delay of one half
motor cycle on the drive output opposed to the former
(figure 4). Due to the debounce circuitry on the RESET
input, VDD must be applied for at least 31.2 ms. During
RESET the input current is limited to 8 nA typically.
A test frequency of 512 Hz is output to this pad which can
be measured with a high resistance probe (R ≥ 10 MW,
C ≤ 20 pF). This signal can be used for testing and tuning
the oscillator. Connecting TEST to VDD for at least 4 ms
changes the motor cycle time from the selected value to
the test cycle time (mask options), while the motor pulse
width remains unchanged (figure 3).
This feature can be used to reduce the amount of time re-
quired for testing the mechanical parts of the watch.
Table 1 Motor options
Cycle time TM
Motor pulse width tM
Motor test cycle time TMT
= 2, 4, 6, 8, 10, 12, 20, 24, 30, 40, 60, 80, 120 s
= 0.98 to 14.65 ms in increments of 0.98 ms
= 250, 125, 62.5 ms
2 (5) Rev. A2, 12-Dec-00