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PT7C4302
Real-time Clock Module (3-wire Interface)
Description
The PT7C4302 serial real-time clock is a low-
power clock/calendar with a programmable square-wave
output and 31 bytes of nonvolatile RAM.
Address and data are transferred serially via a 3-
wire 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.
Table 1 shows the basic functions of PT7C4302.
More details are shown in section: overview of functions.
Features
Using external 32.768kHz quartz crystal
Real-time clock (RTC) counts seconds, minutes
hours, date of the month, month, day of the week,
and year with leap-year compensation valid up to
2099
31-byte, nonvolatile (NV) RAM for data storage
Time keeping voltage: 1.5V to 5.5V
Uses less than 300nA at 2.0V
Simple 3-wire interface
Serial I/O for minimum pin count
Burst mode for reading/writing successive addresses
in clock/RAM
TTL-compatible (VCC = 5V)
Optional industrial temperature range: -40° to
C
+85°
C
Battery backup
Trickle charger on chip for rechargeable energy
source backup
Pin Assignment
PT7C4302
1
VCC2
VCC1
8
2
X1
X2
SCLK
7
3
I/O
RST
6
4
GND
5
Pin Description
Pin no.
1
2
3
4
5
6
7
8
Pin
VCC
2
X1
X2
GND
RST
I/O
SCL
K
VCC
1
Type
P
I
O
P
I
I/
O
I
P
Description
DIP-8
SOIC-8
Primary power.
When V
CC2
is greater than V
CC1
+ 0.2V, V
CC2
will power the IC. While V
CC2
<V
CC1
, V
CC1
will power the IC.
*1
Oscillator Circuit Input.
Together with X2, 32.768kHz crystal is connected between them.
Oscillator Circuit Output.
Together with X1, 32.768kHz crystal is connected between them.
Ground.
Reset.
The reset signal must be asserted high during a read or a write. This pin has a 40kΩ internal pull-
down resistor.
Serial Data Input/Output.
I/O is the input/output pin for the 3-wire serial interface. The pin has a 40k
internal pull-down resistor.
Serial Clock Input.
SCLK is used to synchronize data movement on the 3-wire serial interface. The pin
has a 40k internal pull-down resistor.
Backup power.
When V
CC2
is greater than V
CC1
+ 0.2V, V
CC2
will power the IC. While V
CC2
<V
CC1
, V
CC1
will power the IC.
*1
Note
*1
: If V
CC1
connects to battery, the battery voltage V
CC1
has to be lower than V
CC2
- 0.2Vwhen IC is read and written.
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PT7C4302
Real-time Clock Module (3-wire Interface)
Function Block
PT7C4302
X1
32.768
kHz
C
D
OSC
Counter
Chain
Time Counter
(Sec,Min,Hour,Day,Date,Month,Year)
31 x 8
RAM
X2
C
G
Address
Decoder
Power Manager
VCC2
VCC1
Address
Register
I /O
Interface
(3-wires)
SCLK
RST
I/O
Shift Registers
Note:
C
D
=C
G
=11pF
Maximum Ratings
Storage Temperature…………………………………...-65℃ to +150℃
Ambient Temperature with Power Applied......................-40℃ to +85℃
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
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
Symbol
V
CC1
Description
Backup power voltage
Timing data and RAM data maintaining voltage
Timing data writing voltage
V
CC2
Timing data reading voltage
RAM data writing voltage
RAM data reading voltage
V
IH
V
IL
T
A
Input high level
Input low level
Operating temperature
Min
1.5
1.2
1.5
1.5
3.0
1.5
2
-0.3
-40
Type
-
-
-
-
-
-
-
-
-
Max
5.5
5.5
5.5
5.5
5.5
5.5
V
CC
+0.3
0.3
85
º
C
V
Unit
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PT7C4302
Real-time Clock Module (3-wire Interface)
DC Electrical Characteristics
Unless otherwise specified, GND =0V, T
A
= 25 ° Oscillation frequency = 32.768 kHz.
C,
Sym
V
CC1
Item
Backup power voltage
Timing and RAM data maintaining
V
CC2
Timing data writing voltage
Timing data reading voltage
RAM data writing voltage
RAM data reading voltage
VCC2
Pin
VCC1
-
-
-
-
-
-
OSC on, Note 2, 5
I
CC1
Current consumption
VCC1
OSC on, Note 1, 5
OSC off, Note 4,
5, 7
OSC on, Note 2, 6
I
CC2
Current consumption
VCC2
OSC on, Note 1, 6
OSC off, Note 4, 6
V
IL1
V
IH1
V
IL2
V
IH2
V
OL
V
OH
I
IL
I
OZ
V
TD
R1
R2
R3
Low-level input voltage
High-level input voltage
Low-level input voltage
High-level input voltage
Low-level output voltage
High-level output voltage
Input leakage current
Output current when OFF
Trickle Charge Diode Voltage Drop
Trickle charge resistors
SCL, /RST
SCL, /RST
X1
X1
I/O
I/O
/RST,SCLK
I/O
-
-
-
-
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
Conditions
Min
1.5
1.2
1.5
1.5
3.0
1.5
-
-
-
-
-
-
-
-
-
-
-
-
-
-
2.0
1.4
-
-
2.0
1.4
-
-
1.6
2.4
-
-
-
-
-
-
Typ
-
-
-
-
-
-
-
-
0.5
1
100
100
-
-
-
-
-
-
1.1
0.6
1.3
0.9
1.9
0.9
1.9
0.9
0.08
0.11
1.9
4.9
-
-
0.7
2
4
8
Max
5.5
5.5
5.5
5.5
5.5
5.5
0.4
1.2
-
-
-
-
0.425
1.28
25.3
81
25
80
0.8
0.4
-
-
0.8
0.6
-
-
0.4
0.4
-
-
500
500
-
-
-
-
V
Unit
V
mA
A
nA
mA
A
A
V
V
V
V
V
V
A
A
V
k
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
V
CC1
: 5V
V
CC1
: 2V
I
OH
= 1.5mA, V
CC
= 2V
I
OH
= 4.0mA, V
CC
= 5V
I
OH
= -0.4mA, V
CC
= 2V
I
OH
= -1.0mA, V
CC
= 5V
Note 3
Note 3
-
-
-
-
Note:1.
I/O open, /RST set to a logic 0, and /EOSC bit = 0 (oscillator enabled).
2. I/O pin open, /RST high, SCLK=2MHz at V
CC
= 5V; SCLK = 500kHz, V
CC
= 2.0V, and /EOSC bit = 0 (oscillator
enabled).
3. /RST, SCLK, and I/O all have 40k pull-down resistors to ground.
4. /RST, I/O, and SCLK open. The /EOSC bit = 1 (oscillator disabled).
5. V
CC2
= 0V.
6. V
CC1
= 0V.
7.
Typical values are at 25C.
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PT7C4302
Real-time Clock Module (3-wire Interface)
AC Electrical Characteristics
Figure 6 a Timing diagram: Read data transfer
T
A
= -40 ° to +85 ° Unless otherwise specified.
C
C.
Parameter
Data to CLK Setup
CLK to Data Hold
CLK to Data Delay
CLK Low Time
CLK High Time
CLK Frequency
CLK Rise and Fall
RST to CLK Setup
CLK to RST Hold
RST Inactive Time
RST to I/O High-Z
SCLK to I/O High-Z
t
DC
t
CDH
t
CDD
t
CL
t
CH
t
CLK
t
R
,t
F
t
CC
t
CCH
t
CWH
t
CDZ
t
CCZ
Sym
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
V
CC
=2.0V
V
CC
=5.0V
Min
200
50
280
70
-
-
1000
250
1000
250
-
0
-
-
4
1
240
60
4
1
-
-
-
-
Figure 6 b Timing diagram: Write data transfer
Typ
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Max
-
-
-
-
800
200
-
-
-
-
0.5
2.0
2000
500
-
-
-
-
-
-
280
70
280
70
Unit
ns
ns
ns
ns
ns
MHz
ns
s
ns
s
ns
ns
Notes
1
1
1,2,3
1
1
1
1
1
1
1
1
1
Note:
1. Measured at V
IH
= 2.0V or V
IL
= 0.8V and 10ns maximum rise and fall time.
2. Measured at V
OH
= 2.4V or V
OL
= 0.4V.
3. Load capacitance = 50pF.
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PT7C4302
Real-time Clock Module (3-wire Interface)
Recommended Layout for Crystal
Note:
The crystal, traces and crystal input pins
should be isolated from RF generating signals.
Built-in Capacitors Specifications and Recommended External Capacitors
Symbol
Typ
Unit
X1 to GND
C
G
11
pF
Build-in capacitors
X2 to GND
C
D
11
pF
X1 to GND
C
1
12
pF
Recommended External capacitors for
crystal C
L
=12.5pF
X2 to GND
C
2
12
pF
X1 to GND
C
1
0
pF
Recommended External capacitors for
crystal C
L
=6pF
X2 to GND
C
2
0
pF
Note:
The frequency of crystal can be optimized by external capacitor C
1
and C
2
, for frequency=32.768 KHz, C
1
and C
2
should
meet the equation as below:
Cpar + [(C
1
+C
G
)*(C
2
+C
D
)]/ [(C
1
+C
G
)+(C
2
+C
D
)] =C
L
Cpar is all parasitical capacitor between X1 and X2.
C
L
is crystal’s load capacitance.
Parameter
Crystal Specifications
Parameter
Nominal Frequency
Series Resistance
Load Capacitance
Symbol
f
O
ESR
C
L
Min
-
-
-
Typ
32.768
-
6/12.5
Max
-
70
-
Unit
kHz
k
pF
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