19-3694; Rev 0; 10/05
SPI-Compatible RTC with Microprocessor
Supervisor, Alarm, and NV RAM Controller
General Description
The MAX6916 provides all the features of a real-time
clock (RTC) plus a microprocessor supervisory circuit,
NV RAM controller, and backup-battery monitor func-
tion. In addition, 96 x 8 bits of static RAM are available
for scratchpad storage. The MAX6916 communicates
with a microprocessor through an SPI™-bus-compati-
ble 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 microprocessor supervisory circuit features an
open-drain, active-low reset available in three different
reset thresholds. 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 MAX6916 has a crystal-fail-detect circuit and a
data-valid bit. The MAX6916 is available in a 20-pin
QSOP package and is guaranteed to operate over the
-40°C to +85°C extended temperature range.
Features
o
Real-Time Clock Counts
Seconds, Minutes, Hours, Date, Month, Day of
Week, and Year with Leap-Year Compensation
Through 2099
o
4MHz SPI-Bus-Compatible Interface at 5V, 2MHz
at 3V, and 3.3V
o
SPI Interface Supports Modes 1 and 3 (0, 1 and 1, 1)
o
96 x 8 Bits of RAM for Scratchpad Data Storage
o
Uses Standard 32.768kHz, 6pF Load, Watch
Crystal
o
Single-Byte or Multiple-Byte (Burst Mode) Data
Transfer for Read or Write of Clock Registers or
RAM
o
Battery Monitor and Low-Battery Warning Output
Internal Default for Lithium Backup-Battery
Testing
Pins Available for Other Backup-Battery
Testing Configurations
o
Dual Power-Supply Pins for Primary and Backup
Power
o
Battery-On Output
o
NV RAM Controller
Chip-Enable Gating (Control of
CE
with Reset
and Power Valid)
V
OUT
for SRAM Power
o
µP Supervisor with Watchdog Input
o
Programmable Time/Date Alarm Output
o
Data Valid Bit (Loss of All Voltage Alerts User of
Corrupt Data)
o
Crystal-Fail Detect
o
Small 20-Pin, QSOP Surface-Mount Package
MAX6916
Applications
Point-of-Sale Equipment
Programmable Logic Controllers
Intelligent Instruments
Fax Machines
Digital Thermostats
Industrial Controls
Pin Configuration and Selector Guide appear at end of data
sheet.
SPI is a trademark of Motorola, Inc.
Ordering Information
PART
MAX6916EO30+
MAX6916EO33+
MAX6916EO50+
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.
SPI-Compatible RTC with Microprocessor
Supervisor, Alarm, and NV RAM Controller
MAX6916
ABSOLUTE MAXIMUM RATINGS
V
BATT
, V
CC
to GND ...............................................-0.3V to +6.0V
All Other Pins to GND.................................-0.3V to (V
CC
+ 0.3V)
All Other Pins to GND..............................-0.3V to (V
BATT
+ 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 (T
A
= +70°C)
20-Pin QSOP (derate 9.1mW/°C over +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
MAX6916EO30
MAX6916EO33
MAX6916EO50
MAX6916EO30
Operating Voltage Range BATT
(Note 4)
V
BATT
MAX6916EO33
MAX6916EO50
V
BATT
= 2V, V
CC
= 0
XTAL FAIL
disabled
Timekeeping Current V
BATT
(Note 5)
I
BATT
XTAL FAIL
enabled
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
XTAL FAIL
disabled
Active Supply Current V
CC
(Note 6)
I
CCA
XTAL FAIL
enabled
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
XTAL FAIL
disabled
Standby Current V
CC
(Note 5)
I
CCS
XTAL FAIL
enabled
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
0.35
0.4
1.1
0.36
0.42
1.2
20
25
76
27
30
81
µA
mA
µA
V
V
UNITS
2
_______________________________________________________________________________________
SPI-Compatible RTC with Microprocessor
Supervisor, Alarm, and NV RAM Controller
MAX6916
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
WDI INPUT (Figure 9)
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
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
OL
Output Low Voltage
Off-Leakage
BATT_ON
OUTPUT
V
OL
Output Low Voltage
Off-Leakage
RESET
MAX6916EO30
RESET
Threshold Voltage
V
RST
Hysteresis
V
RST
V
HYST
V
CC
falling from V
RST(MAX)
to V
RST(MIN)
measured from
the beginning of V
CC
falling
to
RESET
low
MAX6916EO30
MAX6916EO33
MAX6916EO50
MAX6916EO33
MAX6916EO50
2.5
2.8
4.1
2.63
2.93
4.38
30
27
37
50
75
90
120
µs
2.7
3.0
4.5
mV
V
V
OL
V
OL
I
LKG
V
BATT
= 2V, V
CC
= 0, I
OL
= 5mA
V
BATT
= 2.7V, V
CC
= 0, I
OL
= 10mA
V
BATT
= 4.5V, V
CC
= 0, I
OL
= 20mA
-100
0.5
0.5
0.5
+100
nA
V
V
OL
V
OL
I
LKG
V
BATT
= 2V, V
CC
= 0, I
OL
= 5mA
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
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)
(Note 5)
Internal mode
V
CC
= V
CC(MAX)
, V
BATT
= 2V,
external mode
2.45
1.14
2.6
1.24
10
External mode
-100
0.5
V
OUT
-
0.3V
0.3
0.91
+100
1.3
2.0
-100
+100
450
nA
µA
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
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
BATTERY TEST AND TRIP (Figures 14, 15, and 16)
V
BTP
V
TRIP
V
TRIP_HYST
I
TRIP_LKG
V
TEST_HIG
H
2.7
1.31
V
V
mV
nA
MΩ
V
V
R
LOAD_INT
Internal
I
TEST
= -5mA
V
TEST_LOW
I
TEST
= 5mA
V
CC
Falling-Reset Delay
t
RPD
4
_______________________________________________________________________________________
SPI-Compatible RTC with Microprocessor
Supervisor, Alarm, and NV RAM Controller
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
Main Reset Active-Timeout Period
RESET
Output-Low Voltage
Off-Leakage
SPI DIGITAL INPUTS DIN, SCLK,
CS
Input High Voltage
Input Low Voltage
Input Hysteresis
Input Leakage Current
Input Capacitance
SPI DIGITAL OUTPUT DOUT
Output High Voltage
Output Low Voltage
Output Capacitance
Output Off-State Leakage Current
I
OZ
V
OH
V
OL
I
OH
= -1.6mA
I
OL
= 1.6mA
(Note 8)
-100
0.9 x V
CC
0.4
10
+100
V
V
pF
nA
V
IH
V
IL
V
HYS
V
IN
= 0 to V
CC
(Note 8)
-100
0.05 x
V
CC
+100
10
2
0.8
V
V
V
nA
pF
SYMBOL
t
RP
V
OL
I
LKG
RESET
asserted, I
OL
= 1.6mA, V
BATT
= 2V,
V
CC
= 0
-100
CONDITIONS
MIN
140
TYP
200
MAX
280
0.2
+100
UNITS
ms
V
nA
MAX6916
AC 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.) (Note 2)
PARAMETER
Maximum-Input Rise Time
Maximum-Input Fall Time
Output Rise Time
Output Fall Time
SLCK Period
SCLK High Time
SCLK Low Time
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
CS
High-to-DOUT High
Impedance
CS
to SCLK Setup Time
BATTERY TEST TIMING (Figure 15)
Battery Test to
BATT_LO
Active
t
BL
(Note 8)
1
s
SYMBOL
t
RIN
t
FIN
t
ROUT
t
FOUT
t
CP
t
CH
t
CL
t
DO
t
DS
t
DH
t
CSH
t
CSW
t
CSZ
t
CSS
100
DIN, SCLK,
CS
DIN, SCLK,
CS
DOUT, C
LOAD
= 100pF
DOUT, C
LOAD
= 100pF
MAX6916EO30, MAX6916EO33
MAX6916EO50
MAX6916EO30, MAX6916EO33
MAX6916EO50
MAX6916EO30, MAX6916EO33
MAX6916EO50
C
LOAD
= 100pF
100
0
0
200
100
500
238
200
100
200
100
100
CONDITIONS
MIN
TYP
2
2
10
10
MAX
UNITS
µs
µs
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
SPI BUS TIMING (Figure 2 (Note 9))
_______________________________________________________________________________________
5
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