PCF85263ATL/A View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
PCF85263ATL/A
NXP Semiconductors.
'PCF85263ATL/A' PDF : 100 Pages View PDF
NXP Semiconductors
PCF85263A
Tiny RTC with alarm, battery switch-over, and I2C-bus
Oscillator circuits suffer from jitter. In particular, ultra low-power oscillators like the one
used in the PCF85263A are optimized for power and not jitter. By setting the LOWJ bit,
the jitter performance can be improved at the cost of power consumption.
8.10.5 OSCD[1:0]: quartz oscillator drive control
Table 34. OSCD[1:0] bits - oscillator control register (address 25h)
Bit
Symbol
Value
Description
3 to 2 OSCD[1:0]
oscillator drive bits
00[1]
01
10, 11
normal drive; RS(max): 100 k
low drive; RS(max): 60 k; reduced IDD
high drive; RS(max): 500 k; increased IDD
[1] Default value.
The oscillator is designed to be used with quartz with a series resistance up to 100 k.
This covers the typical range of 32.768 kHz quartz crystals. Series resistance is also
referred to as: ESR, motional resistance, or RS.
A low drive mode is available for low series resistance quartz. This reduces the current
consumption.
For very high series resistance quartz, there is a high drive mode. Current consumption
increases substantially in this mode.
8.10.6 CL[1:0]: quartz oscillator load capacitance
Table 35. CL[1:0] bits - oscillator control register (address 25h)
Bit
Symbol
Value
Description
1 to 0 CL[1:0]
internal oscillator capacitor selection for
quartz crystals with the corresponding load
capacitance of CL:
00[1]
7.0 pF
01
6.0 pF
10
12.5 pF
11
12.5 pF
[1] Default value.
CL refers to the load capacitance of the oscillator circuit and allows for a certain amount of
package and PCB parasitic capacitance. When the oscillator circuit matches the CL
parameter of the quartz, then the frequency offset is zero.
The PCF85263A is designed to operate with quartz with CL values of 6.0 pF, 7.0 pF and
12.5 pF.
12.5 pF are generally the cheapest and most widely available, but also require the most
power to drive. The circuit also operates with 9.0 pF quartz, however the offset calibration
would be needed to compensate. If a 9.0 pF quartz is used, then it is recommended to set
CL to 7.0 pF.
PCF85263A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 4.1 — 27 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
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