PCA2129T/Q900/2,51 NXP Semiconductors, PCA2129T/Q900/2,51 Datasheet - Page 12

• Manufacturer Part Number: PCA2129T/Q900/2,51
• Description: Real Time Clock
• Manufacturer: NXP Semiconductors
• Series: PCA2129r

Specifications of PCA2129T/Q900/2,51

• Rohs: yes
• Function: Clock, Calendar, Alarm, Watchdog, Timestamp
• Rtc Bus Interface: I2C, SPI
• Date Format: Binary
• Time Format: Binary
• Supply Voltage - Max: 4.2 V
• Supply Voltage - Min: 1.8 V
• Maximum Operating Temperature: + 80 C
• Minimum Operating Temperature: - 30 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-16
• Battery Backup Switching: Yes

NXP Semiconductors
PCA2129T
Product data sheet
8.3.1.1 Temperature measurement
8.3.1 Temperature compensated crystal oscillator
8.3.2 Clock output
8.3 Register CLKOUT_ctl
Table 9.
The frequency of tuning fork quartz crystal oscillators is temperature-dependent. In the
PCA2129T, the frequency deviation caused by temperature variation is corrected by
adjusting the load capacitance of the crystal oscillator.
The load capacitance is changed by switching between two load capacitance values using
a modulation signal with a programmable duty cycle. In order to compensate the spread of
the quartz parameters every chip is factory calibrated.
The frequency accuracy can be evaluated by measuring the frequency of the square
wave signal available at the output pin CLKOUT. However, the selection of
f
frequency measurement occurs when f
Table
The PCA2129T has a temperature sensor circuit used to perform the temperature
compensation of the frequency. The temperature is measured immediately after power-on
and then periodically with a period set by the temperature conversion rate TCR[1:0] in the
register CLKOUT_ctl.
Table 10.
[1]
A programmable square wave is available at pin CLKOUT. Operation is controlled by the
COF[2:0] control bits in register CLKOUT_ctl. Frequencies of 32.768 kHz (default) down
to 1 Hz can be generated for use as system clock, microcontroller clock, charge pump
input, or for calibrating the oscillator.
CLKOUT is an open-drain output and enabled at power-on. When disabled, the output is
high-impedance.
The duty cycle of the selected clock is not controlled, however, due to the nature of the
clock generation all but the 32.768 kHz frequencies will be 50 : 50.
Bit
7 to 6 TCR[1:0]
5 to 3 -
2 to 0 COF[2:0]
TCR[1:0]
00
01
10
11
CLKOUT
Default value.
11).
Symbol
= 32.768 kHz (default value) leads to inaccurate measurements. Accurate
CLKOUT_ctl - CLKOUT control register (address 0Fh) bit description
Temperature measurement period
All information provided in this document is subject to legal disclaimers.
[1]
Rev. 3 — 24 January 2013
Temperature measurement period
4 min
2 min
1 min
30 seconds
Accurate RTC with integrated quartz crystal for automotive
Value
see
-
see
Table 10
Table 11
CLKOUT
Description
temperature measurement period
unused
CLKOUT frequency selection
= 16.384 kHz or lower is selected (see
PCA2129T
© NXP B.V. 2013. All rights reserved.
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