PT7C4337A Datasheet, PDF (7/25 Pages) Pericom Semiconductor Corporation – Real-time Clock Module

PT7C4337A/4337AC
Real-time Clock Module (I²C Bus)
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Function Block
P_PT_T7₇C_C4₄3₃3₃7₇A
X1
32.768
kHz
X2
C_G
OSC
C_D
Counter Chain
Control Register
INTA
SQW/INTB
Interrupt Control
Square Wave Output Control
Comparator 1
Comparator 2
Alarm 1 Register
(Sec, Min, Hour, Day/Date)
Alarm 2 Register
(Min, Hour, Day/Date)
Time Counter
(Sec,Min,Hour,Day,Date,Month,Year)
Address
Decoder
Address
Register
Shift Register
I /O
Interface
(I²C)
SCL
SDA
Oscillator Circuit
PT7C4337A
The PT7C4337A uses an external 32.768 kHz crystal. Table2 specifies several crystal parameters for the external crystal. The
Block Diagram shows a functional schematic of the oscillator circuit. The startup time is usually less than 1 second when using a
crystal with the specified characteristics.
Table2 Crystal Specifications
Parameter
Symbol
Min
Typ
Max
Unit
Nominal Frequency
f_O
-
32.768
-
kHz
Series Resistance
ESR
-
-
70
k
Load Capacitance
C_L
-
6/12.5
-
pF
Note: The crystal, traces, and crystal input pins should be isolated from RF generating signals.
Clock Accuracy
The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match between the capacitive
load of the oscillator circuit and the capacitive load for which the crystal was trimmed. Crystal frequency drift caused by
temperature shifts creates additional error. External circuit noise coupled into the oscillator circuit can result in the clock running
fast. Figure 1 shows a typical PC board layout for isolating the crystal and oscillator from noise.
PT7C4337AC
The PT7C4337AC integrates a standard 32,768Hz crystal in the package. Typical accuracy at nominal VCC and +25°C is
approximately 10ppm.
2014-10-0002
PT0480-2 11/03/14
7