Clock operation

M41T01

16/24

DocID025389 Rev 2

Figure 10. Crystal accuracy across temperature

Figure 11. Clock calibration

3.2

Output driver pin

When the FT bit is set, the FT/OUT pin provides a nominal 512 Hz frequency output used

for calibration purposes (see Section 3.1).

When the FT bit is set to zero, the FT/OUT pin becomes an output driver that reflects the

contents of the OUT bit (D7 bit of register 7, see Table 2). If the OUT bit is zero, then the

FT/OUT pin will be driven low, if the OUT bit is one, then the FT/OUT pin will be driven high.

The OUT bit can be written through the 2-wire bus port.

Note:

The FT/OUT pin is open drain which requires an external pull-up resistor.

3.3

Initial power-on defaults

Upon initial application of power to the device, the FT bit will be set to a '0' and the OUT bit

will be set to a '1'. All other register bits will initially power on in a random state.

AI00999b

–160

0

10203040506070

Frequency (ppm)

Temperature

°C

80

–10

–20

–30

–40

–100

–120

–140

–40

–60

–80

20

0

–20

ΔF

= K x (T –T

2

K = –0.036 ppm/

F

AI00594B

NORMAL

POSITIVE

CALIBRATION

NEGATIVE

CALIBRATION