MAX6902(2003) 查看數據表（PDF） - Maxim Integrated

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MAX6902
(Rev.:2003)

SPI-Compatible RTC in a TDFN

Maxim Integrated 

SPI-Compatible RTC in a TDFN

(TA = +25°C, unless otherwise noted.)

Typical Operating Characteristics

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

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

4 _______________________________________________________________________________________

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