Rainbow Electronics MAX6902 User Manual
General Description
The MAX6902 SPI™-compatible real-time clock contains a real-time clock/calendar and 31 x 8 bits of static
random-access memory (SRAM). The real-time
clock/calendar provides seconds, minutes, hours, day,
date, month, year, and century information. A time/date
programmable polled ALARM is included in the
MAX6902. The end-of-the-month date is automatically
adjusted for months with fewer than 31 days, including
corrections for leap year up to the year 2100. The clock
operates in either the 24hr or 12hr format with an
AM/PM indicator. The MAX6902 operates with a supply
voltage of +2V to +5.5V, is available in the ultra-small
8-pin TDFN package, and works over the -40°C to
+85°C industrial temperature range.
Applications
Point-of-Sale Equipment
Intelligent Instruments
Fax Machines
Battery-Powered Products
Portable Instruments
Features
♦ Real-Time Clock Counts Seconds, Minutes, Hours,
Day of Week, Date of Month, Month, Year, and Century
♦ Leap-Year Compensation Valid up to Year 2100
♦ +2V to +5.5V Wide Operating Voltage Range
♦ SPI Interface: 4MHz at 5V; 1MHz at 2V
♦ 31 x 8-Bit SRAM for Scratchpad Data Storage
♦ Uses Standard 32.768kHz, 12.5pF Watch Crystal
♦ Low Timekeeping Current (400nA at 2V)
♦ Single-Byte or Multiple-Byte (Burst Mode) Data
Transfer for Read or Write of Clock Registers or
SRAM
♦ Ultra-Small 8-Pin 3mm x 3mm x 0.8mm TDFN
Package
♦ Programmable Time/Date Polled ALARM Function
♦ No External Crystal Bias Resistors or Capacitors
Required
MAX6902
SPI-Compatible RTC in a TDFN
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
Ordering Information
Typical Operating Circuit
19-2134; Rev 1; 7/03
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
I2C is a trademark of Philips Corp. Purchase of I2C components of Maxim Integrated Products, Inc., or one of its sublicensed
Associated Companies, conveys a license under the Philips I
2
C Patent rights to use these components in an I2C system provided that
the system conforms to the I
2
C Standard Specification as defined by Philips.
SPI is a trademark of Motorola, Inc.
Related Real-Time Clock Products
TEMP
PART
MAX6902ETA-T -40°C to +85°C 8 TDFN AGT
RANGE
PINPACKAGE
TOP
MARK
PART
MAX6900 I2C™ compatible 31 ✕ 8 ——6 TDFN
MAX6901 3 Wire 31 ✕ 8 Polled 32kHz 8 TDFN
MAX6902 SPI compatible 31 ✕ 8 Polled — 8 TDFN
+3.3V
µc
SERIAL
INTERFACE
+3.3V
0.1µF
6
V
CC
8
GND
4
X1
7
X2
MAX6902
1
SCLK
5
CS
2
DOUT
3
DIN
SRAM
32.768kHz
CRYSTAL
ALARM
FUNCTION
TOP VIEW
OUTPUT
FREQUENCY
1
SCLK
2
3
DIN
4
PACKAGE
87X1
MAX6902
TDFN
X2DOUT
V
6
CC
5
CSGND
PIN-
MAX6902
SPI-Compatible RTC in a TDFN
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(VCC= +2.0V to +5.5V, TA= -40°C to +85°C. Typical values are at VCC= +3.3V, TA= +25°C, unless otherwise noted.) (Note 1)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
VCCto GND..............................................................-0.3V to +6V
All Other Pins to GND ................................-0.3V to (VCC+ 0.3V)
Current into Any Pin..........................................................±20mA
Rate of Rise, VCC............................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
8-Pin TDFN (derate 24.4mW/°C above +70°C) ..........1951.0mW
Junction Temperature .....................................................+150°C
Storage Temperature Range…………………… -65°C to +150°C
ESD Protection (all pins, Human Body Model) ..................2000V
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Operating Voltage
Range
Active Supply
Current (Note 2)
Timekeeping Supply
Current (Note 3)
SPI DIGITAL INPUTS (SCLK, DIN, CS)
Input High Voltage V
Input Low Voltage V
Input Leakage
Input Capacitance 10 pF
SPI DIGITAL OUTPUTS (DOUT)
Output Capacitance 15 pF
Output Low Voltage V
Output High Voltage V
V
CC
I
I
I
CC
TK
IH
IL
IL
OL
OH
VCC = +2V 0.3
VCC = +5V 1.1
VCC = +2V 0.4 0.8
VCC = +5V 1.3 2.2
VCC = +2V 1.4
VCC = +5V 2.2
VCC = +2V 0.6
VCC = +5V 0.8
VIN = 0 to V
VCC = +2.0V, I
VCC = +5.0V, I
VCC = +2.0V, I
VCC = +5.0V, I
CC
= 1.5mA 0.4
SINK
= 4mA 0.4
SINK
= -0.4mA 1.8
SOURCE
= -1mA 4.5
SOURCE
2 5.5 V
-10 10 nA
mA
µA
V
V
V
V
MAX6902
SPI-Compatible RTC in a TDFN
_______________________________________________________________________________________ 3
AC ELECTRICAL CHARACTERISTICS
(VCC= +2.0V to +5.5V, TA= -40°C to +85°C. Typical values are at VCC= +3.3V, TA= +25°C, unless otherwise noted.) (Figure 5,
Notes 1, 4)
Note 1: All parameters are 100% tested at TA= +25°C. Limits over temperature are guaranteed by design and characterization and
not production tested.
Note 2: I
CC
is specified with DOUT open, CS = DIN = GND, SCLK = 4MHz at VCC= +5V; SCLK = 1MHz at VCC= +2.0V.
Note 3: Timekeeping current is specified with CS = V
CC
, SCLK = DIN = GND, DOUT = 100kΩ to GND.
Note 4: All values referred to V
IH
min and VILmax levels.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OSCILLATOR
X1 to Ground
Capacitance
X2 to Ground
Capacitance
SPI SERIAL TIMING
Maximum Input Rise
Time
Maximum Input Fall
Time
Output Rise Time t
Output Fall Time t
SCLK Period t
SCLK High Time t
SCLK Low Time t
SCLK Fall to DOUT
Valid
DIN to SCLK Setup
Time
DIN to SCLK Hold
Time
SCLK Rise to CS
Rise Hold Time
CS High Pulse Width t
CS High to DOUT
High Impedance
CS to SCLK Setup
Time
t
rIN
t
fIN
rOUT
fOUT
CP
CH
CL
t
DO
t
DS
t
DH
t
CSH
CSW
t
CSZ
t
CSS
DIN, SCLK, CS 2 µs
DIN, SCLK, CS 2 µs
DOUT, C
DOUT, C
VCC = +2V 1000
VCC = +5V 238
C
LOAD
= 100pF 10 ns
LOAD
= 100pF 10 ns
LOAD
100 ns
100 ns
= 100pF 100 ns
100 ns
2ns
2ns
200 ns
100 ns
25 pF
25 pF
ns
100 ns
MAX6902
Detailed Description
The MAX6902 is a real-time clock/calendar with an SPIcompatible interface and 31 x 8 bits of SRAM. It provides seconds, minutes, hours, day of the week, date of
the month, month, and year information, held in seven 8bit timekeeping registers (Functional Diagram). An onchip 32.768kHz oscillator circuit requires only a single
external crystal to operate. Table 1 specifies the parameters 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
SPI-Compatible RTC in a TDFN
4 _______________________________________________________________________________________
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
Pin Description
Figure 1. Crystal Oscillator Circuit Schematic
10.0
TIMEKEEPING CURRENT
vs. SUPPLY VOLTAGE
MAX6902 toc01
PIN NAME FUNCTION
1 SCLK
2 DOUT SPI Data Output
3 DIN SPI Data Input
4 GND Ground
5 CS
6V
7 X2 External 32.768kHz Crystal
8 X1 External 32.768kHz Crystal
Serial Clock Input. SPI clock for DIN and
DOUT data transfers.
Chip Select Input. Active low for valid data
transfers.
Power-Supply Pin. Bypass VCC to GND
CC
with a 0.1µF capacitor.
1.0
SUPPLY CURRENT (µA)
0.1
2.0 3.5 4.02.5 3.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
PARAMETER SYMBOL MIN TYP MAX UNITS
Frequency f 32.768 kHz
Equivalent
Series
Resistance
(ESR)
Parallel Load
Capacitance
Q Factor Q 40,000 60,000
R
S
C
L
40 60 kΩ
11.2 12.5 13.7 pF
MAX6902
25pF
X1 X2
EXTERNAL
CRYSTAL
25pF
MAX6902
SPI-Compatible RTC in a TDFN
_______________________________________________________________________________________ 5
Figure 2. Register Address Definition (Sheet 1 of 3)
REGISTER ADDRESS REGISTER DEFINITION
FUNCTION A7 A6 A5 A4 A3 A2 A1 A0 VALUE D7 D6 D5 D4 D3 D2 D1 D0
CLOCK
SECONDS RD 0000001 00-59
/W *POR STATE 0 000 0000
MINUTES RD 0000011 00-59
/W *POR STATE 0 0 0 0 0 0 0 0
HOURS RD 0000101 00-23 12/24
/W 01-12 1/0
*POR STATE 0 0 00 0 0 0 0
01-28/29
DATE RD 0000111
/W *POR STATE 0 0 000001
MONTH RD 0001001 01-12 0 0 0 10M 1 MONTH
/W *POR STATE 0 0 0 00001
01-30
0-31
0 10 SEC 1 SEC
ALM
OUT
0 0 10 DATE 1 DATE
10 MIN 1 MIN
10
HR
A/P
0/1
10
HR
0
1 HR
DAY RD 0001011 01-07 0 0 0 0 0 WEEK DAY
/W *POR STATE 0 0 0 0 0 001
YEAR RD 0001101 00-99 10 YEAR 1 YEAR
/W *POR STATE 0 1 1 1 0000
CONTROL RD 0001111 WP 0 0 0 0 0 0 0
/W *POR STATE 0 0 0 0 0 0 0 0
CENTURY RD 0010011 00-99 1000 YEAR 100 YEAR
/W *POR STATE 0 0 0 1 1001
Note: *POR STATE d efi nes p ow er - on r eset state of r eg i ster contents.
MAX6902
SPI-Compatible RTC in a TDFN
6 _______________________________________________________________________________________
Figure 2. Register Address Definition (Sheet 2 of 3)
REGISTER ADDRESS REGISTER DEFINITION
FUNCTION A7 A6 A5 A4 A3 A2 A1 A0 VALUE D7 D6 D5 D4 D3 D2 D1 D0
ALARM
CONFIG
RESERVED RD 0010111 0 0 0 0 0 1 1 1
Do not write
to this location.
ALARM
THRESHOLDS
SECONDS RD 0011001 00-59
MINUTES RD 0011011 00-59 0 10 MIN 1 MIN
HOURS RD 0011101 00-23 12/24
DATE RD 0011111
RD 0010101
/W *POR STATE 0 0 0 0 0 0 0 0
/W *POR STATE 00000111
/W *POR STATE 0 11 1 11 1 1
/W *POR STATE 0 111111 1
/W 01-12 1/0
*POR STATE 1 0 111111
01-28/29
01-30
01-31
/W *POR STATE 0 0 111111
0
0 10 SEC 1 SEC
0 0 10 DATE 1 DATE
0
YEAR
10HR10
A/P
0/1
DAY
MONTH
HR
DATE
HOUR
1 HR
MINUTE
SECOND
MONTH RD 0100001 01-12 0 0 0 10M 1 MONTH
/W *POR STATE 0 0 0 11111
DAY RD 0100011 01-07 0 0 0 0 0 WEEK DAY
/W *POR STATE 0 0 0 0 0 11 1
YEAR RD 0100101 00-99 10 YEAR 1 YEAR
/W *POR STATE 1 1 1 1 1 1 1 1
CLOCK
BURST
RD 0111111
/W
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