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PCF1179CT
4-digit duplex LCD car clock
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
FEATURES Internal voltage regulator is electrically programmable
for various LCD voltages Time calibration is electrically programmable
(no trimming capacitor required) LCD voltage adjusts with temperature for good contrast 4.19 MHz oscillator 12-hour or 24-hour mode Operating ambient temperature: −40to +85°C 28-lead plastic SMD (SO28)4 Hz set mode.
GENERAL DESCRIPTIONThe PCF1179C is a single chip, 4.19 MHz CMOS car clock
circuit providing hours, minutes and seconds functions.
It is designed to drive a 4-digit duplex liquid crystal display
(LCD).
Two external single-pole, single-throw switches will
accomplish all time setting functions. Time calibration and
voltage regulator are electrically programmable via an
on-chip EEPROM. The circuit is battery-operated via an
internal voltage regulator and an external resistor.
ORDERING INFORMATION
Notes See Fig.1 and Chapter “Package outline” for pin layout and package details. See Chapter “Chip dimensions and bonding pad locations” for pad layout and package details.
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
PINNING
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
FUNCTIONAL DESCRIPTION AND TESTING
OutputsThe circuit outputs 1:2 multiplexed data (duplex) to the
LCD. Generation of BP1 and BP2 (three-level backplane
signals) and the output signals are shown in Fig.4.
The average voltages across the segments are: VON(RMS)= 0.79 VDD VOFF(RMS)= 0.35 VDD.
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
LCD voltage (see Fig.5)
The adjustable voltage regulator controls the supply
voltage (see Section “LCD voltage programming”) in
relation to temperature for good contrast, for example
when VDD= 4.5 V at +25 °C, then:
VDD=3to4 V at +85 °C.
VDD=5to6 V at −40 °C.
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
12/24-hour modeOperation in 12-hour or 24-hour mode is selected by
connecting MODE to VDD or VSS respectively. If MODE is
left open-circuit and a reset occurs, the mode will change
from 12-hour to 24-hour mode or vice versa.
Power-onAfter connecting the supply, the start-up mode is:
MODE connected to VDD: 12-hour mode, 1:00 AM.
MODE connected to VSS: 24-hour mode, 0:00.
MODE left open-circuit: 24-hour mode, 0:00or 1:00.
ColonIf FLASH is connected to VDD the colon pulses at 1 Hz.
If FLASH is connected to VSS the colon is static.
Time settingSwitch inputs S1 and S2 have a pull-up resistor to facilitate
the use of single-pole, single-throw contacts. A debounce
circuit is incorporated to protect against contact bounce
and parasitic voltages.
Set enableInputs S1 and S2 are enabled by connecting ENABLE to
VDD or disabled by connecting to VSS.
Set hoursWhen S1 is connected to VSS the hours displayed
advances by one and after one second continues with four
advances per second until S1 is released
(auto-increment). An overflow in the hour counter must not
have an influence on the minute counter.
Set minutesWhen S2 is connected to VSS the time displayed in
minutes advances by one and after one second continues
with four advances per second until S2 is released
(auto-increment). In addition to minute correction, the
seconds counter is reset to zero. An overflow in the minute
counter must not have an influence on the hour counter.
Segment test/resetWhen S1 and S2 are connected to VSS, all LCD segments
are switched ON. Releasing switches S1 and S2 resets the
display. No reset occurs when DATA is connected to VSS
(overlapping S1 and S2).
Test modeWhen TS is connected to VDD, the device is in normal
operating mode. When connecting TS to VSS all counters
(seconds, minutes and hours) are stopped, allowing quick
testing of the display via S1 and S2 (debounce and
auto-increment times are 64 times faster). TS has a
pull-up resistor but for reasons of safety it should be
connected to VDD.
EEPROMVPP has a pull-up resistor but for reasons of safety it should
be connected to VDD.
LCD voltage programmingTo enable LCD voltage programming, SEL is set to
open-circuit and a level of VDD−5 V is applied to VPP (see
Fig.6). The first pulse (tE) applied to the DATA input clears
the EEPROM to give the lowest voltage output. Further
pulses (tL) will increment the output voltage by steps of
typically 150 mV (Tamb =25 °C). For programming,
measure VDD− VSS and apply a store pulse (tW) when the
required value is reached. If the maximum number of steps= 31) is reached and an additional pulse is applied the
voltage will return to the lowest value.
Time calibrationTo compensate for the tolerance in the quartz crystal
frequency which has been positively offset (nominal
deviation +60×10−6 by capacitors at the oscillator input
and output, a number (n) of 262144 Hz pulses are
inhibited every second of operation.
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
The number (n) is stored in a non-volatile memory which is achieved by the following steps (see Fig.6): Set SEL to VSS and a level of VDD−5 V to VPP The quartz-frequency deviation Δf/f is measured and (n) is calculated (see Table1) A first pulse tE is applied to the DATA input clears the EEPROM to give the highest backplane frequency The calculated pulses (n) are entered in (tH, tL). If the maximum backplane period is reached and an additional pulse
is applied the period will return to the lowest value. The backplane period is controlled and when correct fixed by applying the store pulse tW Release SEL and VPP.
Table 1 Time calibration (Δt= 7.63 μs; SEL at VSS)
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
LIMITING VALUESIn accordance with the Absolute Maximum Rating System (IEC 134).
Note Connecting the supply voltage with reverse polarity, will not harm the circuit, provided the current is limited to 10 mA
by an external resistor.
HANDLINGInputs and outputs are protected against electrostatic discharges in normal handling. However, to be totally safe, it is
advisable to take handling precautions appropriate to handling MOS devices. Advice can be found in
“Data Handbook IC16, General, Handling MOS Devices”.
Philips Semiconductors Product specification
4-digit duplex LCD car clock PCF1179C
CHARACTERISTICSVDD =3to6V; VSS =0V; Tamb= −40to +85 °C; crystal: f= 4.194304 MHz; Rs =50 Ω; CL=12 pF; maximum
frequency tolerance= ±30×10−6 ; unless otherwise specified.
Note A suitable resistor (R) must be selected (example): VDD = 5 V; R max. (12 V − 5 V)/700 μA = 10 kΩ. VDD = 5 V; R typ. (12 V − 5 V)/900 μA = 7.8 kΩ (more reserve). IDD must not exceed 3 mA.
