Datasheet

15
ICM7228
Three Level Input, ICM7228C
As mentioned before, pin 9 is a three level input and controls
three functions: Hexadecimal display decoding, Code B
display decoding and shutdown mode. In many applications,
pin 9 will be left open or permanently wired to one state. When
pin 9 can not be permanently left in one state, the circuits
illustrated in Figure 17 can be used to drive this three level
input.
Power Supply Bypassing
Connect a minimum of 47µF in parallel with 0.1µF capacitors
between V
DD
and V
SS
of ICM7228. These capacitors
should be placed in close proximity to the device to reduce
the power supply ripple caused by the multiplexed LED
display drive current pulses.
V
DD
ICM7228B
100Ω
SEGMENT
OUTPUT
300Ω
DIGIT
OUTPUT
N
V
SS
≈15Ω
1K
2N2219
(100mA
PEAK
)
25Ω
2N6034
1.4A
PEAK
1K
V
DD
V
SS
1K
V
DD
V
DD
FIGURE 16. DRIVING HIGH CURRENT DISPLAY, COMMON
CATHODE ICM7228B TO COMMON ANODE
DISPLAY
HIGH = HEX
LOW = SHUTDOWN
HIGH = HEX OR SHUTDOWN
LOW = CODE B
HIGH = HEX
LOW = SHUTDOWN
HIGH = HEX OR SHUTDOWN
LOW = CODE B
HIGH = CODE B
LOW = HEX
HIGH = SHUTDOWN
LOW = CODE B
HIGH = SHUTDOWN
LOW = HEX
HIGH = SHUTDOWN
LOW = CODE B
PIN 9
PIN 9
PIN 9
PIN 9
PIN 9
PIN 9
CD4016
CD4066
CONTROL
CD4069
CD4069
CD4069
1N4148
1N4148
OPEN DRAIN OR OPEN
COLLECTOR OUTPUT
74C126 THREE-STATE BUFFER
FIGURE 17. ICM7228C PIN 9 DRIVE CIRCUITS