PCF8523 NXP [NXP Semiconductors], PCF8523 Datasheet - Page 17

• Manufacturer Part Number: PCF8523
• Description: Real-Time Clock (RTC) and calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCF8523
Product data sheet
8.5.2.2 Direct switching mode
8.5.2.3 Battery switch-over disabled, only one power supply (V
8.5.3 Battery low detection function
If V
If V
The direct switching mode is useful in systems where V
(e.g. V
and V
power consumption is reduced compared to the standard mode because the monitoring of
V
When the battery switch-over function is disabled:
The PCF8523 has a battery low detection circuit, which monitors the status of the battery
V
Generation of interrupts from the battery low detection is controlled via bit BLIE (register
Control_3). If BLIE is enabled the INT1 will follow the status of bit BLF (register
Control_3).
When V
(register Control_3) is set to indicate that the battery is low and that it must be replaced.
Monitoring of the battery voltage also occurs during battery operation.
Fig 10. Battery switch-over behavior in direct switching mode and with bit BSIE set
DD
BAT
•
•
•
V
DD
DD
DD
V
The power supply is applied on the V
The V
The battery flag (BSF) is always logic 0.
(= 2.5 V)
and V
th(sw)bat
.
(= 0 V)
BAT
INT1
> V
< V
DD
V
BSF
V
BAT
BAT
DD
logic 1 (enabled)
= 5 V, V
values are similar (e.g. V
BAT
BAT
BAT
th(sw)bat
backup battery operation
drops below the threshold value V
the internal power supply is V
the internal power supply is V
pin must be connected to ground.
All information provided in this document is subject to legal disclaimers.
BAT
is not performed.
V
BBS
= 3.5 V). The direct switching mode is not recommended if the V
Rev. 3 — 30 March 2011
DD
= 3.3 V, V
internal power supply (= V
DD
DD
BAT
pin.
.
th(bat)low
.
BAT
Real-Time Clock (RTC) and calendar
 3.0 V). In direct switching mode the
(typically 2.5 V) the BLF flag
DD
BBS
is higher than V
DD
)
)
cleared via interface
PCF8523
© NXP B.V. 2011. All rights reserved.
BAT
at all times
013aaa322
V
17 of 66
BBS
DD