19-3702; Rev 1; 10/05
I
2
C-Compatible RTC with Microprocessor
Supervisor, Alarm, and NV RAM Controller
General Description
The MAX6917 provides all the features of a real-time
clock (RTC) plus a microprocessor (µP) supervisory cir-
cuit, NV RAM controller, and backup-battery monitor
function. In addition, 96 x 8 bits of static RAM are avail-
able for scratchpad storage. The MAX6917 communi-
cates with a µP through an I
2
C-bus-compatible serial
interface.
The real-time clock/calendar provides seconds, min-
utes, hours, day, date, month, and year information.
The end of the month date is automatically adjusted for
months with fewer than 31 days, including corrections
for leap years through 2099. The clock operates in
either 24hr or 12hr format with an AM/PM indicator. A
time/date-programmable alarm function is provided
with an open-drain, active-low alarm output.
The µP supervisory circuit features an open-drain,
active-low reset available in three different reset thresh-
olds. A manual reset input and a watchdog function are
included as well.
The NV RAM controller provides power for external SRAM
from a backup battery plus chip-enable gating. The back-
up battery also provides data retention of the on-board 96
x 8 bits of RAM. An open-drain, active-low, battery-on sig-
nal alerts the system when operating from a battery.
The battery-test circuitry periodically tests the backup
battery for a low-battery condition. An optional external
resistor network selects different battery thresholds. A
freshness seal prevents battery drain until the first V
CC
power-up.
The MAX6917 has a crystal-fail-detect circuit and a
data-valid bit. The MAX6917 is available in a 20-pin
QSOP package and is guaranteed to operate over the
extended (-40°C to +85°C) temperature range.
Features
♦
Real-Time Clock Counts
Seconds, Minutes, Hours, Date,
Month, Day of Week, and Year
with Leap-Year Compensation Through 2099
♦
Fast (400kHz) I
2
C-Bus-Compatible Interface
♦
96 x 8 Bits of RAM for Scratchpad Data Storage
♦
Uses Standard 32.768kHz, 6pF Load, Watch
Crystal
♦
Single-Byte or Multiple-Byte (Burst Mode) Data
Transfer for Read or Write of Clock Registers or
RAM
♦
Battery Monitor and Low-Battery Warning Output
Internal Default for Lithium Backup-Battery
Testing
Pins Available for Other Backup-Battery
Testing Configurations
♦
Dual Power-Supply Pins for Primary and Backup
Power
♦
Battery-On Output
♦
NV RAM Controller
Chip-Enable Gating (Control of
CE
with Reset
and Power Valid)
V
OUT
for SRAM Power
♦
Microprocessor Supervisor with Watchdog Input
♦
Programmable Time/Date Alarm Output
♦
Data Valid Bit (Loss of All Voltage Alerts User of
Corrupt Data)
♦
Crystal-Fail Detect
♦
Reference Output Frequencies—1Hz and
32.768kHz
♦
Small, 20-Pin, QSOP Surface-Mount Package
MAX6917
Applications
Point-of-Sale Equipment
Programmable Logic Controllers
Intelligent Instruments
Fax Machines
Digital Thermostats
Industrial Control
Pin Configuration and Selector Guide appear at end of data
sheet.
Ordering Information
PART
MAX6917EO30+
MAX6917EO33+
MAX6917EO50+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
20 QSOP
20 QSOP
20 QSOP
PKG
CODE
E20-2
E20-2
E20-2
+Denotes
lead-free package.
________________________________________________________________
Maxim Integrated Products
1
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.
I
2
C-Compatible RTC with Microprocessor
Supervisor, Alarm, and NV RAM Controller
MAX6917
ABSOLUTE MAXIMUM RATINGS
V
BATT
, V
CC
to GND ...............................................-0.3V to +6.0V
All Other Pins to GND ................................-0.3V to (VCC + 0.3V)
All Other Pins to GND ............................-0.3V to (VBATT + 0.3V)
Input Currents
V
CC
..................................................................................200mA
V
BATT
.................................................................................20mA
GND ....................................................................................20mA
All Other Pins ....................................................................±20mA
Output Currents
V
OUT
Continuous ..........................................................200mA
All Other Outputs ............................................................20mA
Continuous Power Dissipation
20-Pin QSOP (derate 9.1mW/°C over T
A
= +70°C) .....727mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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.
DC ELECTRICAL CHARACTERISTICS
(V
CC
= V
CC(MIN)
to V
CC(MAX)
, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Operating Voltage Range
(Note 3)
SYMBOL
V
CC
CONDITIONS
MAX6917EO30
MAX6917EO33
MAX6917EO50
MAX6917EO30
Operating Voltage Range BATT
(Note 4)
V
BATT
MAX6917EO33
MAX6917EO50
1Hz, 32kHz
outputs disabled;
XTAL FAIL
disabled
1Hz, 32kHz
outputs disabled;
XTAL FAIL
enabled
1Hz, 32kHz
enabled, outputs
open; XTAL FAIL
disabled
1Hz, 32kHz
enabled, outputs
open; XTAL FAIL
enabled
1Hz, 32kHz
outputs disabled;
XTAL FAIL
disabled
V
BATT
= 2V, V
CC
= 0
V
BATT
= 3V, V
CC
= 0
V
BATT
= 3.6V, V
CC
= 0
V
BATT
= 5.5V, V
CC
= 0
V
BATT
= 2V, V
CC
= 0
V
BATT
= 3V, V
CC
= 0
V
BATT
= 3.6V, V
CC
= 0
V
BATT
= 5.5V, V
CC
= 0
V
BATT
= 2V, V
CC
= 0
V
BATT
= 3V, V
CC
= 0
V
BATT
= 3.6V, V
CC
= 0
V
BATT
= 5.5V, V
CC
= 0
V
CC
= 3.3V, V
BATT
= 0
V
CC
= 3.6V, V
BATT
= 0
V
CC
= 5.5V, V
BATT
= 0
V
CC
= 3.3V, V
BATT
= 0
V
CC
= 3.6V, V
BATT
= 0
V
CC
= 5.5V, V
BATT
= 0
MIN
2.7
3.0
4.5
2.0
2.0
2.0
TYP
3.0
3.3
5.0
MAX
3.3
3.6
5.5
5.5
5.5
5.5
1
1.4
1.9
3.8
1.23
1.61
2.3
4.08
2.82
4.7
6.1
10.6
0.1
0.12
0.2
mA
0.9
0.11
0.18
µA
V
V
UNITS
Timekeeping Current V
BATT
(Note 5)
I
BATT
Active Supply Current V
CC
(Note 6)
I
CCA
2
_______________________________________________________________________________________
I
2
C-Compatible RTC with Microprocessor
Supervisor, Alarm, and NV RAM Controller
MAX6917
DC ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
CC(MIN)
to V
CC(MAX)
, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
CE_OUT
Active-Low Delay After
V
CC
> V
RST
CE_OUT
High Voltage
MR
INPUT (Figure 10)
MR
Input Voltage
MR
Pullup Resistance
MR
Minimum Pulse Width
MR
Glitch Immunity
MR
to
RESET
Delay
WDI INPUT (Figure 12)
WDI Initial Timeout Period
Watchdog Timeout Period
Minimum WDI Input Pulse Width
WDI Input Threshold
WDI Input-Leakage Current
V
CC
Standby Current with WDI
Max Frequency
I
CCSW
t
WDL
t
WDS
t
WDI
V
IL
V
IH
V
WDI
= V
CC
or GND
Watchdog frequency = 1MHz,
V
CC
= V
CC(MAX)
, 1Hz, 32kHz outputs
disabled (Note 5)
2.0
-100
+100
450
V
CC
> V
RST
from rising edge of
RESET
Long watchdog timeout period
Short watchdog timeout period
1.00
1.00
140
100
0.8
1.6
1.6
200
2.25
2.25
280
s
s
ms
ns
V
nA
µA
t
GW
t
RD
V
CC
= V
CC(MIN)
, V
BATT
= 0
450
V
IL
V
IH
Internal pullup resistor
1
35
600
2.0
50
0.8
V
kΩ
µs
ns
ns
SYMBOL
t
RP
V
OH
I
OH
= -100µA, V
BATT
= 2V, V
CC
= 0,
RESET
= low
CONDITIONS
MIN
140
0.8 x
V
BATT
TYP
200
MAX
280
UNITS
ms
V
BATTERY TEST AND TRIP (Figures 17, 18, and 19)
V
BATT
Trip Point
TRIP Input Threshold
TRIP Input Comparator
Hysteresis
TRIP Input Current
Battery Test Load
TEST Output-High Voltage
TEST Output-Low Voltage
BATT_LO, ALM
OUTPUT
V
BATT
= 2V, V
CC
= 0, I
OL
= 5mA
Output Low Voltage
Off-Leakage
V
OL
I
LKG
V
CC
= 2.7V, V
BATT
= 0, I
OL
= 10mA
V
CC
= 4.5V, V
BATT
= 0, I
OL
= 20mA
-100
0.5
0.5
0.5
+100
nA
V
V
BTP
V
TRIP
V
TRIP_HYST
I
TRIP_LKG
R
LOAD_INT
External mode
Internal
-100
0.50
V
OUT
-
0.3V
0.3
0.91
Internal mode
V
CC
= V
CC(MAX)
, V
BATT
= 2V,
external mode
2.45
1.14
2.6
1.24
10
+100
1.30
2.70
1.31
V
V
mV
nA
MΩ
V
V
V
TEST_HIGH
I
TEST
= -5mA
V
TEST_LOW
I
TEST
= 5mA
4
_______________________________________________________________________________________
PCB Design
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