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PT7C433833
Real-time Clock Module (I
2
C Bus
)
Product Features
Using external 32.768kHz quartz crystal
Supports I
2
C-Bus's high speed mode (400 kHz)
Includes time (Hour/Minute/Second) and calendar
(Year/Month/Date/Day) counter functions (BCD
code)
Programmable square wave output signal
56-byte, battery-backed, nonvolatile (NV) RAM for
data storage
Automatic power-fail detect and switch circuitry of
battery backup
UL Recognized: E348121
Product Description
The PT7C4338 serial real-time clock is a low-power
clock/calendar with a programmable square-wave output
and 56 bytes of nonvolatile RAM.
Address and data are transferred serially via a 2-wire,
bidirectional bus. The clock/calendar provides seconds,
minutes, hours, day, date, month, and year information.
The date at the end of the month is automatically
adjusted for months with fewer than 31 days, including
corrections for leap year. The clock operates in either the
24-hour or 12-hour format with AM/PM indicator.
The PT7C4338 series have a built-in power sense circuit
that detects power failures and automatically switches to
the battery supply.
Table 1 shows the basic functions of PT7C4338. More
details are shown in section: overview of functions.
Table 1.
Basic functions of PT7C4338
Item
Function
Source: Crystal: 32.768kHz
1
Oscillator
Oscillator enable/disable
Oscillator fail detect
12-hour
Time display
2
Time
Century bit
3
4
5
6
Alarm interrupt
Programmable square wave output (Hz)
RAM
Battery backup
24-hour
PT7C4338
-
-
1, 4.096k, 8.192k, 32.768k
568
12-07-0001
1
PT0321-6
07/04/12
PT7C433833
Real-time Clock Module (I
2
C Bus)
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Pin Assignment
PT7C4338
1
X1
X2
VBAT
GND
VCC
SQW/OUT
SCL
SDA
8
2
7
3
6
4
5
SOIC-8
MSOP-8
Pin Description
Pin no.
1
Pin
X1
Type
I
Description
32.768kHz Crystal Connections.
The internal oscillator circuitry is designed for operation with
a crystal having a specified load capacitance (CL) of 12.5pF. Pin X1 is the input to the oscillator
and can optionally be connected to an external 32.768kHz oscillator. The output of the internal
oscillator, pin X2, is floated if an external oscillator is connected to pin X1. An external
32.768kHz oscillator can also drive the PT7C4338. In this configuration, the X1 pin is connected
to the external oscillator signal and the X2 pin is floated.
Serial Clock Input.
SCL is used to synchronize data movement on the I
2
C serial interface.
Serial Data Input/Output.
SDA is the input/output pin for the 2-wire serial interface. The SDA
pin is open-drain output and requires an external pull-up resistor.
Square-Wave/Output Driver.
When enabled and the SQWE bit set to 1, the SQW/OUT pin
outputs one of four square-wave frequencies (1Hz, 4kHz, 8kHz, 32kHz). It is open drain and
requires an external pull up resistor. Operates with either VCC or VBAT applied.
Supply Voltage.
When voltage is applied within normal limits, the device is fully accessible and
data can be written and read. When a backup supply is connected to the device and VCC is
below VPF, reads and writes are inhibited. However, the timekeeping function continues
unaffected by the lower input voltage.
+3V Battery Input.
Backup supply input for any standard 3V lithium cell or other energy
source. Battery voltage must be held between the minimum and maximum limits for proper
operation. If a backup supply is not required, VBAT must be grounded.
UL
recognized to ensure
against reverse charging when used with a lithium battery.
Ground.
DC power is provided to the device on these pins. VCC is the primary power input.
When voltage is applied within normal limits, the device is fully accessible and data can be
written and read. When a backup supply is connected to the device and VCC is below VPF, reads
and writes are inhibited. However, the timekeeping function continues unaffected by the lower
input voltage.
2
6
5
X2
SCL
SDA
O
I
I/O
7
SQW/OUT
O
8
VCC
P
3
VBAT
P
4
GND
P
12-07-0001
2
PT0321-6
07/04/12
PT7C433833
Real-time Clock Module (I
2
C Bus)
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Function Block
Maximum Ratings
Storage Temperature ...............................................................................................................-55oCto +125oC
Ambient Temperature with Power Applied ......................................................................-40oCto +85oC
Supply Voltage to Ground Potential (Vcc to GND) ..................................................... -0.3V to +6.5V
DC Input (All Other Inputs except Vcc & GND)........................................................... -0.3V to +6.5V
DC Output Voltage (SDA, /INTA, /INTB pins) ..............................................................-0.3V to +6.5V
DC Output Current (FOUT)..................................................................................................-0.3V to (V
cc
+0.3V)
Power Dissipation ....................................................................................................................320mW (depend on package)
Note:
Stresses greater than those listed under MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and
functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not
implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
Recommended Operating Conditions
(V
CC
= V
CC(MIN)
to V
CC(MAX)
, T
A
= -40℃ to +85℃.) (Note 1)
Parameter
Symbol
Conditions
Min.
Supply Voltage
V
CC
PT7C433833
2.7
Logic 1
V
IH
Note 2
0.7 * V
CC
Logic 0
V
IL
Note 2
-0.3
Power-Fail Voltage
V
PF
PT7C433833
-
V
BAT
Battery Voltage
V
BAT
Note 2
1.5
Note 1:
Limits at -40° are guaranteed by design and not production tested.
C
Note 2:
All voltages are referenced to ground.
12-07-0001
3
Typ.
3.3
-
-
2.59
3.0
Max.
5.5
V
CC
+ 0.3
+0.3 * V
CC
-
3.7
Unit
V
PT0321-6
07/04/12
PT7C433833
Real-time Clock Module (I
2
C Bus)
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DC Electrical Characteristics
(V
CC
= V
CC(MIN)
to V
CC(MAX)
, T
A
= -40℃ to +85℃.) (Note 1)
Parameter
V
BAT
Battery Voltage
Input Leakage
I/O Leakage
SDA Logic 0 Output
Symbol
V
BAT
I
LI
I
LO
I
OLSDA
Conditions
Note 2
Note 3
Note 4
V
CC
> 2V; V
OL
= 0.4V
V
CC
< 2V; V
OL
= 0.2 V
CC
V
CC
> 2V; V
OL
= 0.4V
1.71V < V
CC
< 2V; V
OL
= 0.2 V
CC
1.5V < V
CC
< 1.71V; V
OL
= 0.2 V
CC
PT7C433833
PT7C433833
-
Min.
1.5
-
-
3.0
3.0
3.0
3.0
250
-
-
-
Typ.
-
-
-
-
-
-
-
-
120
85
25
Max.
3.7
1
1
-
-
-
-
-
200
125
100
Unit
V
μA
μA
mA
mA
μA
μA
μA
nA
SQW/OUT Logic 0 Output
Active Supply Current (Note 5)
Standby Current (Note 6)
V
BAT
Leakage Current (V
CC
Active)
I
OLSQW
I
CCA
I
CCS
I
BATLKG
(V
CC
= 0V, T
A
= -40℃ to +85℃.) (Note 1)
Parameter
V
BAT
Current (OSC ON); V
BAT
=3.7V, SQW/OUT OFF (Note 7)
V
BAT
Current (OSC ON); V
BAT
=3.7V, SQW/OUT ON (32kHz) (Note 7)
V
BAT
Data-Retention Current (OSC OFF); V
BAT
=3.7V (Note 7)
Note 1:
Limits at -40° are guaranteed by design and not production tested.
C
Note 2:
All voltages are referenced to ground.
Note 3:
SCL only.
Note 4:
SDA and SQW/OUT.
Note 5:
ICCA------SCL clocking at max frequency = 400kHz.
Note 6:
Specified with the I2C bus inactive.
Note 7:
Measured with a 32.768kHz crystal attached to X1 and X2.
Symbol
I
BATOSC1
I
BATOSC2
I
BATDAT
Min.
-
-
-
Typ.
400
570
-
Max.
1200
1400
300
Unit
nA
nA
nA
AC Electrical Characteristics
Sym
V
HM
V
HL
Description
Rising and falling threshold voltage high
Rising and falling threshold voltage low
Value
0.7 V
CC
0.3 V
CC
Unit
V
V
Measurement level
Signal
V
HM
V
LM
t
f
t
r
12-07-0001
4
PT0321-6
07/04/12
PT7C433833
Real-time Clock Module (I
2
C Bus)
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(T
A
= -40℃ to +85℃) (Note 1)
Conditions
Min.
Typ.
Max.
Unit
Fast mode
100
-
400
SCL Clock Frequency
f
SCL
kHz
Standard mode
-
-
100
Fast mode
1.3
-
-
Bus Free Time Between STOP and
t
BUF
μs
START condition
Standard mode
4.7
-
-
Fast mode
0.6
-
-
Hold Time (Repeated) START Condition
t
HD:STA
μs
(Note 2)
Standard mode
4.0
-
-
Fast mode
1.3
-
-
LOW Period of SCL Clock
t
LOW
μs
Standard mode
4.7
-
-
Fast mode
0.6
-
-
HIGH Period of SCL Clock
t
HIGH
μs
Standard mode
4.0
-
-
Fast mode
0.6
-
-
Setup Time of Repeated START
t
SU:STA
μs
Condition
Standard mode
4.7
-
-
Fast mode
0
-
0.9
Data Hold Time (Note 3, 4)
t
HD:STA
μs
Standard mode
0
-
-
Fast mode
100
-
-
Data Setup Time (Note 5)
ns
t
SU:STA
Standard mode
250
-
-
Fast mode
20+0.1C
B
-
300
Rise Time of Both SDA and SCL Signals
t
r
ns
(Note 6)
Standard mode
20+0.1C
B
-
1000
Fast mode
20+0.1C
B
-
300
Fall Time of Both SDA and SCL Signals
t
f
ns
(Note 6)
Standard mode
20+0.1C
B
-
300
Fast mode
0.6
-
-
Setup Time for STOP Condition
μs
t
SU:STO
Standard mode
4.0
-
-
Capacitance Load for Each Bus Line
Note 6
-
-
400
pF
C
B
I/O Capacitance (SDA, SCL)
Note 1
-
-
10
pF
C
I/O
Oscillator Stop Flag (OSF) Delay
Note 7
-
100
-
ms
t
OSF
Note 1:
Limits of full temperature are guaranteed by design not production test.
Note 2:
After this period, the first clock pulse is generated.
Note 3:
A device must internally provide a hold time of at least 300ns for the SDA signal (referred to the V
IHMIN
of the SCL signal)
to bridge the undefined region of the falling edge of SCL.
Note 4:
The maximum t
HD:DAT
need only be met if the device does not stretch the LOW period (t
LOW
) of the SCL signal.
Note 5:
A fast-mode device can be used in a standard-mode system, but the requirement t
SU:DAT
≥ to 250ns must then be met. This
is automatically the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch
the LOW period of the SCL signal, it must output the next data bit to the SDA line t
r MAX
+ t
SU:DAT
= 1000 + 250 =
1250ns before the SCL line is released.
Note 6:
C
B
------total capacitance of one bus line in pF.
Note 7:
The parameter t
OSF
is the time period the oscillator must be stopped for the OSF flag to be set over the voltage range of
0.0V ≤ VCC ≤ VCC MAX and 1.3V ≤ VBAT ≤ 3.7V.
Parameter
Symbol
12-07-0001
5
PT0321-6
07/04/12
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