TC7136ACKW Microchip Technology, TC7136ACKW Datasheet - Page 11

• Manufacturer Part Number: TC7136ACKW
• Description: IC ADC 3 1/2DGT LOW PWR 44-MQFP
• Manufacturer: Microchip Technology

Specifications of TC7136ACKW

• Display Type: LCD
• Configuration: 7 Segment
• Digits Or Characters: A/D 3.5 Digits
• Current - Supply: 70µA
• Voltage - Supply: 9V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 44-MQFP, 44-PQFP
• Lead Free Status / RoHS Status: Request inventory verification / Request inventory verification
• Interface: -

5.0
The TC7136/A contains all the segment drivers neces-
sary to directly drive a 3-1/2 digit LCD. An LCD back-
plane driver is included. The backplane frequency is
the external clock frequency divided by 800. For three
conversions per second, the backplane frequency is
60Hz with a 5V nominal amplitude. When a segment
driver is in phase with the backplane signal, the seg-
ment 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 polar-
ity segment driver is ON for negative analog inputs. If
V
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.
The display font and segment drive assignment are
shown in Figure 5-1.
FIGURE 5-1:
5.1
The oscillator frequency is divided by 4 prior to clocking
the internal decade counters. The four-phase mea-
surement cycle takes a total of 4000 counts, or 16,000
clock pulses. The 4000 count cycle is independent of
input signal magnitude.
© 2005 Microchip Technology Inc.
IN
Note:
+ and V
DIGITAL SECTION
System Timing
1000's
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.
IN
- are reversed, this indicator would
100's
Display Font
DISPLAY FONT AND
SEGMENT ASSIGNMENT
10's
1's
Each phase of the measurement cycle has the
following length:
1.
2.
This time period is fixed. The integration period is:
EQUATION 5-1:
3.
4.
The TC7136 is a drop-in replacement for the TC7126
and ICL7126. The TC7136A offers a greatly improved
internal reference temperature coefficient. Minor com-
ponent value changes are required to upgrade existing
designs and improve the noise performance.
6.0
6.1
The C
noise. A 0.47μF capacitor is recommended for 200mV
full scale applications, where 1LSB is 100μV. A 0.1μF
capacitor is adequate for 2V full scale applications. A
Mylar type dielectric capacitor is adequate.
6.2
The reference voltage, used to ramp the integrator out-
put voltage back to zero during the reference integrate
phase, is stored on C
able when V
Common mode voltage exists (V
mon) and the application requires a 200mV full scale,
increase C
than 0.5 count. A Mylar type dielectric capacitor is
adequate.
6.3
C
voltage swing without causing output saturation. Ana-
log common will normally supply the differential voltage
reference in this case, a ±2V full scale integrator output
swing is satisfactory. For 3 readings per second
(F
one reading per second, 0.15μF is recommended. If a
different oscillator frequency is used, C
changed in inverse proportion to maintain the nominal
±2V integrator swing.
INT
OSC
Where:
F
OSC
Auto-zero phase: 3000 to 2900 counts
(1200 to 11,600 clock pulses)
Signal integrate: 1000 counts
(4000 clock pulses)
Reference integrate: 0 to 2000 counts
Zero integrator: 11 to 640 counts
should be selected to maximize integrator output
AZ
= 48kHz), a 0.047μF value is suggested. For
is the externally set clock frequency.
COMPONENT VALUE
SELECTION
Auto-Zero Capacitor (C
Reference Voltage Capacitor
(C
Integrating Capacitor (C
capacitor size has some influence on system
TC7136/TC7136A
REF
REF
REF
to 1μF. Rollover error will be held to less
)
- is tied to analog common. If a large
t
SI
= 4000
REF
. A 0.1μF capacitor is accept-
⎛
⎝
F
OSC
1
REF
⎞
⎠
DS21461C-page 11
- ≠ analog com-
AZ
INT
INT
)
)
must be