PCF2131
Nano-power highly accurate RTC with integrated quartz
crystal
Rev. 1.1 — 15 October 2021
Product data sheet
1
General description
The PCF2131 is a CMOS Real Time Clock (RTC) and calendar with an integrated
Temperature Compensated Crystal (Xtal) Oscillator (TCXO) and a 32.768 kHz quartz
crystal optimized for very high accuracy and ultra low power consumption. The
2
PCF2131 has a selectable I C-bus or SPI-bus, a backup battery switch-over circuit, a
programmable watchdog function, four timestamps function, and many other features.
For a selection of NXP Real-Time Clocks, see
Section 15.1.
2
Features and benefits
•
Operating temperature range from -40 °C to +85 °C
•
Temperature Compensated Crystal Oscillator (TCXO) with trimmed integrated
capacitors
•
Ultra low supply current: typical 64 nA at V
DD
= 3.3 V
•
Temperature compensated RTC, typical accuracy ±3 ppm from -40 °C to +85 °C
•
Integration of a 32.768 kHz quartz crystal and oscillator in the same package
•
Provides year, month, day, weekday, hours, minutes, seconds and 1/100 seconds
•
Provides leap year correction
•
Timestamp function
–
with interrupt capability
–
detection of four different events on four input pins (for example, for tamper detection)
2
•
2-line bidirectional 400 kHz Fast-mode I C-bus interface
•
4-line SPI-bus with separate data input and output (maximum speed 6.5 Mbit/s)
•
Battery backup input pin and switch-over circuitry
•
Battery backed output voltage
•
Battery low detection function
•
Power-On Reset (POR)
•
Power-On Reset Override (PORO) function
•
Software reset function
•
Two interrupt outputs (open-drain)
•
Programmable 1 second or 1 minute interrupt
•
Programmable watchdog timer with interrupt
•
Programmable alarm function with interrupt capability
•
Programmable square output
•
Clock operating voltage: 1.2 V to 5.5 V
NXP Semiconductors
Nano-power highly accurate RTC with integrated quartz crystal
PCF2131
3
Applications
•
•
•
•
•
•
Electronic metering for electricity, water, and gas
Precision timekeeping
Access to accurate time of the day
GPS equipment to reduce time to first fix
Applications that require an accurate process timing
Products with long automated unattended operation time
4
Ordering information
Package
Name
HLSON16
Description
thermal enhanced low profile small outline; no leads, 16
terminals, 0.125 dimple wettable flank, 0.5 mm pitch,
4.5 mm x 3.5 mm x 1.45 mm body
Version
SOT1992-1
Table 1. Ordering information
Type number
Topside
marking
PCF2131TF
F31
4.1 Ordering options
Table 2. Ordering options
Product type
Orderable part
number
number
PCF2131TF
PCF2131TFY
Package
HLSON16
Packing method
REEL 13" Q1 DP
Minimum
Order
Quantity
4000
Temperature
T
amb
= -40 °C to +85 °C
PCF2131
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© NXP B.V. 2021. All rights reserved.
Product data sheet
Rev. 1.1 — 15 October 2021
2 / 86
NXP Semiconductors
Nano-power highly accurate RTC with integrated quartz crystal
PCF2131
5
Block diagram
INTA / INTB
TEMP
DIVIDER
AND
TIMER
TCXO
100 Hz
Control_1
Control_2
Control_3
Control_4
Control_5
Sofware Reset
1/100thSeconds
Seconds
Minutes
Hours
Days
Weekdays
Months
OSCILLATOR
MONITOR
RESET
ADDRESS
REGISTER
Years
Second_alarm
Minute_alarm
SPI-BUS
INTERFACE
SDA/CE
SDO
SDI
SCL
IFS
TS1
TS2
TS3
TS4
Hour_alarm
Day_alarm
Weekday_alarm
CLKOUT_ctl
SERIAL BUS
INTERFACE
SELECTOR
Timestp_ctl 1/2/3/4
Sec_timestp 1/2/3/4
Min_timestp 1/2/3/4
Hour_timestp 1/2/3/4
Day_timestp 1/2/3/4
R
PU 1/2/3/4
Mon_timestp 1/2/3/4
Year_timestp 1/2/3/4
Aging_offset
TEMP
TEMPERATURE
SENSOR
INT_A_MASK 1/2
INT_B_MASK 1/2
Watchdg_tim_ctl
Watchdg_tim_val
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
12h
13h
14h/1Bh/22h/29h
15h/1Ch/23h/2Ah
16h/1Dh/24h/2Bh
17h/1Eh/25h/2Ch
18h/1Fh/26h/2Dh
19h/20h/27h/2Eh
1Ah/21h/28h/2Fh
30h
31h/32h
33h/34h
35h
36h
aaa-041884
OSCO
32.768 kHz
OSCI
CLKOUT
VDD
VBAT
VSS
BBS
DIVIDER
LOGIC
CONTROL
internal operating
voltage V
oper(int)
BATTERY BACK UP
SWITCH-OVER
CIRCUITRY
I2C-BUS
INTERFACE
PCF2131
Figure 1. Block diagram of PCF2131
PCF2131
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© NXP B.V. 2021. All rights reserved.
Product data sheet
Rev. 1.1 — 15 October 2021
3 / 86
NXP Semiconductors
Nano-power highly accurate RTC with integrated quartz crystal
PCF2131
6
Pinning information
6.1 Pinning
IFS
SCL
SDI
SDO
SDA/CE
CLKOUT
V
SS
TS1
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
BAT
V
DD
BBS
INTA
INTB
TS4
TS3
TS2
PCF2131
aaa-041885
Figure 2. Pin configuration for PCF2131 (transparent top view)
6.2 Pin description
Table 3. Pin description
Input or input/output pins must always be at a defined level (V
SS
or V
DD
) unless otherwise specified.
Symbol
SCL
SDI
SDO
SDA/CE
IFS
Pin
2
3
4
5
1
Description
combined serial clock input for both I C-bus and SPI-bus
serial data input for SPI-bus
2
connect to pin V
SS
if I C-bus is selected
serial data output for SPI-bus, push-pull
2
leave open or connect to pin V
SS
if I C-bus is selected
combined serial data input and output for the I C-bus and chip enable
input (active LOW) for the SPI-bus
interface selector input
connect to pin V
SS
to select the SPI-bus
2
connect to pin V
DD
to select the I C-bus
timestamp input (active LOW) with 500 kΩ internal pull-up resistor (R
PU
)
clock output (push-pull)
ground supply voltage
interrupt B output (open-drain; active LOW)
interrupt A output (open-drain; active LOW)
output voltage (battery backed)
2
2
TS1,TS2,TS3,TS4,
CLKOUT
V
SS
INTB
INTA
BBS
8,9,10,11
6
7
12
13
14
PCF2131
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© NXP B.V. 2021. All rights reserved.
Product data sheet
Rev. 1.1 — 15 October 2021
4 / 86
NXP Semiconductors
Nano-power highly accurate RTC with integrated quartz crystal
Table 3. Pin description
...continued
Input or input/output pins must always be at a defined level (V
SS
or V
DD
) unless otherwise specified.
Symbol
V
BAT
V
DD
Exposed Pad
[1]
PCF2131
Pin
16
15
Description
battery supply voltage (backup)
connect to V
SS
if battery switch-over is not used
supply voltage
Tie to V
SS
(preferred)
[1]
or leave floating
This protects against signal feedback to the oscillator if routed close to the part.
7
Functional description
The PCF2131 is a Real Time Clock (RTC) and calendar with an on-chip Temperature
Compensated Crystal (Xtal) Oscillator (TCXO) and a 32.768 kHz quartz crystal integrated
into the same package.
Address and data are transferred by a selectable 400 kHz Fast-mode I C-bus or a 4-line
SPI-bus with separate data input and output (see
Section 7.16).
The maximum speed of
the SPI-bus is 6.5 Mbit/s.
The PCF2131 has a backup battery input pin and backup battery switch-over circuit
which monitors the main power supply. The backup battery switch-over circuit
automatically switches to the backup battery when a power failure condition is detected
(see
Section 7.5.1).
Accurate timekeeping is maintained even when the main power
supply is interrupted.
A battery low detection circuit monitors the status of the battery (see
Section 7.5.2).
When the battery voltage drops below a certain threshold value, a flag is set to indicate
that the battery must be replaced soon. This ensures the integrity of the data during
periods of battery backup.
2
7.1 Register overview
The PCF2131 contains an auto-incrementing address register: the built-in address
register will increment automatically after each read or write of a data byte up to the
register 36h. After register 36h, the auto-incrementing will wrap around to address 00h
(see
Figure 3).
address register
00h
01h
02h
03h
...
34h
35h
36h
wrap around
aaa-041564
auto-increment
Figure 3. Handling address registers
•
The first five registers (memory address 00h, 01h, 02h, 03h and 04h) are used as
control registers (see
Section 7.2).
PCF2131
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2021. All rights reserved.
Product data sheet
Rev. 1.1 — 15 October 2021
5 / 86
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