MAX6902 查看數據表（PDF） - Maxim Integrated
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MAX6902 Datasheet PDF : 20 Pages
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SPI-Compatible RTC in a TDFN
Typical Operating Characteristic
(TA = +25°C, unless otherwise noted.)
TIMEKEEPING CURRENT
vs. SUPPLY VOLTAGE
10.0
1.0
0.1
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
Pin Description
PIN NAME
FUNCTION
1
SCLK
Serial Clock Input. SPI clock for DIN and
DOUT data transfers.
2 DOUT SPI Data Output
3
DIN SPI Data Input
4
GND Ground
5
CS
Chip Select Input. Active low for valid data
transfers.
6
VCC
Power-Supply Pin. Bypass VCC to GND
with a 0.1µF capacitor.
7
X2 External 32.768kHz Crystal
8
X1 External 32.768kHz Crystal
Exposed Paddle. Internally connected to
GND. Connect to GND, but do not use as
—
EP the sole ground connection point or leave
unconnected.
Detailed Description
The MAX6902 is a real-time clock/calendar with an SPI-
compatible interface and 31 x 8 bits of SRAM. It pro-
vides seconds, minutes, hours, day of the week, date of
the month, month, and year information, held in seven 8-
bit timekeeping registers (Functional Diagram). An on-
chip 32.768kHz oscillator circuit requires only a single
external crystal to operate. Table 1 specifies the para-
meters for the external crystal, and Figure 1 shows a
functional schematic of the oscillator circuit. The
MAX6902’s register addresses and definitions are
described in Figure 2 and in Table 2. Time and calendar
data are stored in the registers in binary-coded decimal
(BCD) format. A polled alarm function is included for
scheduled timing of user-defined times or intervals.
Table 1. Acceptable Quartz Crystal
Parameters
PARAMETER SYMBOL MIN TYP MAX UNITS
Frequency
f
32.768
kHz
Equivalent
Series
Resistance
(ESR)
RS
40
60
kΩ
Parallel Load
Capacitance
Q Factor
CL
11.2 12.5 13.7
pF
Q
40,000
60,000
MAX6902
25pF
25pF
X1
X2
EXTERNAL
CRYSTAL
Figure 1. Crystal Oscillator Circuit Schematic
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