Datasheet > 1339

1339

更新时间： 2023-12-20 18:45:24

品牌	Logo	应用领域
瑞萨 - RENESAS		/
页数	文件大小	规格书
28页	1070K
描述
Real-Time Clock With Serial I2C Interface

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1339 数据手册

1339 Datasheet

Typical Operating Circuit

CRYSTAL

V_CC

R_PU

V_CC

10k

SCL

SQW/INT

V_BACKUP

CPU

1339

SDA

GND

Detailed Description

The following sections discuss in detail the Oscillator block,

Power Control block, Clock/Calendar Register, Alarms,

trickle Charger, and Serial I²C block.

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 32kHz crystal to work

with 1339 RTC are:

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).

• Recommended Load Capacitance

• Crystal Effective Series Resistance (ESR)

• Frequency Tolerance

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.

Note: The 1339CSRI integrates a standard 32.768kHz

(±20ppm) crystal in the package and contributes an

additional frequency error of 10ppm at nominal V_CC(+3.3V)

and T_A=+25°C.

April 4, 2023

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