TC7136 View Datasheet(PDF) - TelCom Semiconductor Inc => Microchip
Part Name
Description
Manufacturer
TC7136 Datasheet PDF : 12 Pages
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TC7136
TC7136A
INT
DENT
ZI
AZ
1000
1–2000
4000
11–140
910–2900
LOW POWER, 3-1/2 DIGIT
ANALOG-TO-DIGITAL CONVERTERS
System Timing
The oscillator frequency is divided by 4 prior to clocking
the internal decade counters. The four-phase measure-
ment cycle takes a total of 4000 counts, or 16,000 clock
DISPLAY FONT
1000's 100's
10's
1's
Figure 4. Conversion Timing During Normal Operation
INT
DEINT
ZI
AZ
1000
2001–2090
31–640
4000
300–910
Figure 5. Conversion Timing During Overrange Operation
DIGITAL SECTION
The TC7136/A contains all the segment drivers neces-
sary to directly drive a 3-1/2 digit LCD. An LCD backplane
driver is included. The backplane frequency is the external
clock frequency divided by 800. For three conversions per
second the backplane frequency is 60 Hz with a 5V nominal
amplitude. When a segment driver is in-phase with the
backplane signal, the segment is OFF. An out-of-phase
segment drive signal causes the segment to be ON, or
visible. This AC drive configuration results in negligible DC
voltage across each LCD segment, ensuring long LCD life.
The polarity segment driver is ON for negative analog inputs.
If VI+N and VI–N are reversed, this indicator would reverse.
On the TC7136/A, when the TEST pin is pulled to V+, all
segments are turned ON. The display reads –1888. During
this mode the LCD segments have a constant DC voltage
impressed. DO NOT LEAVE THE DISPLAY IN THIS MODE
FOR MORE THAN SEVERAL MINUTES. LCDS MAY BE
DESTROYED IF OPERATED WITH DC LEVELS FOR
EXTENDED PERIODS.
The display font and segment drive assignment are
shown in Figure 6.
3-254
Figure 6. Display FONT and Segment Assignment
pulses. The 4000-count cycle is independent of input signal
magnitude.
Each phase of the measurement cycle has the following
length:
(1) Auto-zero phase: 3000 to 2900 counts
(1200 to 11,600 clock pulses)
(2) Signal integrate: 1000 counts
(4000 clock pulses)
This time period is fixed. The integration period is:
1
tSI = 4000
,
fOSC
where fOSC is the externally-set clock frequency.
(3) Reference integrate: 0 to 2000 counts
(4) Zero integrator: 11 to 640 counts
The TC7136 is a drop-in replacement for the TC7126
and ICL7126. The TC7136A offers a greatly-improved inter-
nal reference temperature coefficient. Minor component
value changes are required to upgrade existing designs and
improve the noise performance.
COMPONENT VALUE SELECTION
Auto-Zero Capacitor (CAZ)
The CAZ capacitor size has some influence on system
noise. A 0.47 µF capacitor is recommended for 200 mV full-
scale applications where 1 LSB is 100 µV. A 0.1 µF capacitor
is adequate for 2V full-scale applications. A Mylar-type
dielectric capacitor is adequate.
Reference Voltage Capacitor (CREF)
The reference voltage, used to ramp the integrator
TELCOM SEMICONDUCTOR, INC.
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