MAX6900 Maxim, MAX6900 Datasheet - Page 13

• Manufacturer Part Number: MAX6900
• Description: I2C-Compatible RTC in a TDFN
• Manufacturer: Maxim

RAM burst mode is specified, no data transfer occurs
to any of the RAM locations. Burst writes of data greater
than 31 bytes could cause erroneous data in the
MAX6900.
The MAX6900 contains an integral POR circuit that
ensures all registers are reset to a known state on
power-up. Once V
circuit releases the registers for normal operation.
When V
resets all register contents to the POR defaults.
The MAX6900 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 is a
validation of proper startup.
This is reserved for factory testing ONLY. Do not write
to this register. If inadvertent Writes are done to this
register, cycle power on the MAX6900.
Connect a 32.768kHz watch crystal directly to the
MAX6900 through pin 2 and pin 3 (X1, X2). Use a crys-
Table 4. Quartz Crystal Parameters
Table 5. Crystal Manufacturers
Abracon Corporation
Caliber Electronics
ECS INC International
Fox Electronics
M-tron
Raltron
SaRonix
Frequency
Equivalent Series Resistance (ESR)
Parallel Load Capacitance
Q Factor
MANUFACTURER
CC
drops to less than 1.6V (typ), the MAX6900
PARAMETER
______________________________________________________________________________________
CC
rises above 1.6V (typ), the POR
ABS25-32.768-12.5-B-
AWS2A-32.768KHz
ECS-.327-12.5-17
FSM327
SX2010/SX2020
RSE-32.768-12.5-C-T
32S12A
MANUFACTURER
Power-On Reset (POR)
PART NO.
Reserved Register
Oscillator Startup
Crystal Selection
I
2
SYMBOL
C-Compatible RTC in a TDFN
C
R
Q
f
s
L
-40°C to +85°C
-20°C to +70°C
-10°C to +60°C
-40°C to +85°C
-20°C to +75°C
-10°C to +60°C
-40°C to +85°C
RANGE
TEMP.
tal with a specified load capacitance (C
See Table 4 for a list of crystal parameters.
Table 5 lists some crystal manufacturers and part num-
bers for their surface-mount 32.768kHz watch crystals
that require 12.5pF. In addition, these manufacturers
offer other package options depending upon the spe-
cific application considerations.
Timekeeping accuracy of the MAX6900 is dependent
on the frequency stability of the external crystal. To
Figure 9. Oscillator Functional Schematic
40,000
11.2
MIN
40
Frequency Stability Overtemperature
25pF
MAX6900
Cg
32.768
TYP
12.5
C
L
12.5
12.5
12.5
12.5
12.5
12.5
12.5
(pF)
X1
EXTERNAL
CRYSTAL
Rf
60,000
X2
MAX
13.7
60
+25°C FREQUENCY
TOLERANCE (ppm)
Rd
Cd
25pF
L
±20
±20
±20
±20
±20
±20
±20
) of 12.5pF.
UNITS
kHz
kΩ
pF
13