User Manual

MAX6901
∆t
total
= ∆t
drift
+ ∆t
initial
∆t
total
= 0.00002+0.000025=0.000045s/s
After 1 month, that translates to:
Total worst-case timekeeping error at the end of 1
month at +45°C is about 120s or 2 min (assumes negli-
gible parasitic layout capacitance).
Oscillator Start Time
The MAX6901 oscillator typically takes 5s to 10s to
begin oscillating. To ensure the oscillator is operating
correctly, the software should validate proper time-
keeping. This is accomplished by reading the Seconds
register. Any reading of 1s or more from the POR value
of zero is a validation of proper startup.
Power-On Reset
The MAX6901 contains an integral POR circuit that
ensures all registers are reset to a known state on
power-up. Once V
CC
rises above 1.6V (typ), the POR
circuit releases the registers for normal operation. When
∆t days
hr
day hr
s
ss s
=
()
×






×






×






×
()
=
31 24 60 60
0 00045 120 528
min
min
./.
3-Wire Serial RTC in a TDFN
14 ______________________________________________________________________________________
Figure 4. 3-Wire Read Data Transfer Serial Timing Diagram
01701
CS
SCLK
I/O
t
CC
t
DC
t
CDD
t
CDZ
t
CDD
t
CCZ
t
CDH
READ ADDRESS/COMMAND BYTE READ DATA BIT
Figure 5. 3-Wire Write Data Transfer Serial Timing Diagram
CS
SCLK
I/O
t
CC
t
DC
t
CDH
t
CWH
t
CL
t
CDH
WRITE ADDRESS/COMMAND BYTE WRITE DATA BIT
t
R
t
F
t
CCH
017 0