1339-2DVGI IDT, 1339-2DVGI Datasheet - Page 3

• Manufacturer Part Number: 1339-2DVGI
• Description: Real Time Clock RTC BASE
• Manufacturer: IDT

Specifications of 1339-2DVGI

• Rohs: yes
• Part # Aliases: IDT1339-2DVGI

Typical Operating Circuit
Detailed Description
The following sections discuss in detail the Oscillator block,
Power Control block, Clock/Calendar Register, Alarms,
trickle Charger, and Serial I
Oscillator Block
Selection of the right crystal, correct load capacitance and
careful PCB layout are important for a stable crystal
oscillator. Due to the optimization for the lowest possible
current in the design for these oscillators, losses caused by
parasitic currents can have a significant impact on the
overall oscillator performance. Extra care needs to be taken
to maintain a certain quality and cleanliness of the PCB.
Crystal Selection
The key parameters when selecting a 32 kHz crystal to work
with IDT1339 RTC are:
•
•
•
Effective Load Capacitance
Please see diagram below for effective load capacitance
calculation. The effective load capacitance (CL) should
match the recommended load capacitance of the crystal in
order for the crystal to oscillate at its specified parallel
resonant frequency with 0ppm frequency error.
IDT® REAL-TIME CLOCK WITH SERIAL I
IDT1339
REAL-TIME CLOCK WITH SERIAL I
Recommended Load Capacitance
Crystal Effective Series Resistance (ESR)
Frequency Tolerance
2
C block.
CPU
V
CC
2
C INTERFACE
2
C INTERFACE
R
2k
PU
R
2k
PU
V
CC
5
6
1
SCL
SDA
CRYSTAL
X1
3
IDT1339
In the above figure, X1 and X2 are the crystal pins of our
device. Cin1 and Cin2 are the internal capacitors which
include the X1 and X2 pin capacitance. Cex1 and Cex2 are
the external capacitors that are needed to tune the crystal
frequency. Ct1 and Ct2 are the PCB trace capacitances
between the crystal and the device pins. CS is the shunt
capacitance of the crystal (as specified in the crystal
manufacturer's datasheet or measured using a network
analyzer).
Note: IDT1339CSRI integrates a standard 32.768 kHz
(±20ppm) crystal in the package and contributes an
additional frequency error of 10ppm at nominal
and T
X2
GND
2
4
A
=
+25°C.
SQW/INT
V
V
8
V
BACKUP
CC
CC
7
3
+
-
10k
IDT1339
REV R 121012
V
CC
(+3.3 V)
RTC