7106_15 Datasheet, PDF (11/18 Pages) Unisonic Technologies – CONVERTERS

7106
CMOS IC
„ DETAILED DESCRIPTION(Cont.)
DIGITAL SECTION
Fig.5 show the digital section for the UTC 7106, respectively. In the UTC 7106, an internal digital ground is
generated from a 6V Zener diode and a large P-Channel source follower. This supply is made stiff to absorb the
relative large capacitive currents when the back plane(BP) voltage is switched. The BP frequency is the clock
frequency divided by 800. For three readings/sec, this is a 60Hz square wave with a nominal amplitude of 5V. The
segments are driven at the same frequency and amplitude and are in phase with BP when OFF, but out of phase
when ON. In all cases negligible DC voltage exists across the segments.
a
a
fb
g
b
ec
d
a
fb
g
ec
d
a
fb
g
ec
d
21
BACKPLANE
TYPICAL SEGMENT OUTPUT
V+
0.5mA
2mA
SEGMENT
OUTPUT
INTERNAL DIGITAL GROUND
LCD PHASE DRIVER
7
7
7
SEGMENT SEGMENT SEGMENT
DECODE DECODE DECODE
÷200
LATCH
,
,
,
,
1000 s
100 s
10 s
1s
COUNTER COUNTER COUNTER COUNTER
TO SWITCH DRIVERS
FROM COMPARATOR OUTPUT
CLOCK
*
÷4
INTERNAL
DIGITAL
GROUND
LOGIC
CONTROL
VTH=1V
1
V+
6.2V
500Ω
37
TEST
* THREE INVERTERS ONE INVERTER SHOWN FOR CLARITY
40
39
38
V-
26
OSC 1
OSC 2
OSC 3
Fig.5 Digital Section
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
11 of 18
QW-R502-018.E