tc7107a Microchip Technology Inc., tc7107a Datasheet - Page 11

• Manufacturer Part Number: tc7107a
• Description: 3-1/2 Digit Analog-to-digital Converters
• Manufacturer: Microchip Technology Inc.

6.0
Figure 6-2 shows a TC7107A block diagram. It is
designed to drive common anode LEDs. It is identical
to the TC7106A, except that the regulated supply and
backplane drive have been eliminated and the segment
drive is typically 8mA. The 1000’s output (Pin 19) sinks
current from two LED segments, and has a 16mA drive
capability.
In both devices, the polarity indication is “ON” for
negative analog inputs. If V
this indication can be reversed also, if desired.
The display font is the same as the TC7106A.
6.1
The oscillator frequency is divided by 4 prior to clocking
the
measurement cycle takes a total of 4000 counts, or
16,000 clock pulses. The 4000-count cycle is indepen-
dent of input signal magnitude.
Each phase of the measurement cycle has the follow-
ing length:
1.
For signals less than full scale, the auto-zero phase is
assigned the unused reference integrate time period:
2.
This time period is fixed. The integration period is:
EQUATION 6-1:
3.
The TC7106A/7107A are drop-in replacements for the
7106/7107 parts. External component value changes
are not required to benefit from the low drift internal
reference.
6.2
Three clocking methods may be used (see Figure 6-1):
1.
2.
3.
© 2006 Microchip Technology Inc.
Where: F
Auto-zero phase: 1000 to 3000 counts (4000 to
12000 clock pulses).
Signal integrate: 1000 counts (4000 clock
pulses).
Reference Integrate: 0 to 2000 counts (0 to 8000
clock pulses).
An external oscillator connected to Pin 40.
A crystal between Pins 39 and 40.
An RC oscillator using all three pins.
internal
DIGITAL SECTION (TC7107A)
System Timing
Clock Circuit
OSC
decade
is the externally set clock frequency.
T
SI
= 4000
counters.
IN
⎛
⎝
- and V
F
OSC
1
⎞
⎠
IN
The
+ are reversed,
four-phase
FIGURE 6-1:
EXT
OSC
TC7106/A/TC7107/A
RC Network
40
Crystal
To TEST Pin on TSC7106A
To GND Pin on TSC7107A
TC7106A
TC7107A
Clock Circuits
39
DS21455C-page 11
38
÷
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