IH6208
Switching Information (Continued)
+15V
+3V
50%
t
V
A
S
S
1b
2b
-2V
+0.8V
SWITCH
A
A
1
THRU
OUTPUT
S
3b
V
OUT
0
t
IH6208
OPEN
OPEN
(SEE PINOUT)
0
V
A
S
+5V
EN
4b
0.9V
O
V
D
OUT
35pF
2
200Ω
V
O
GND
V
S
-15V
FIGURE 2. t
(BREAK-BEFORE-MAKE) SWITCHING TEST CIRCUIT AND WAVEFORMS
OPEN
+5V
50%
+15V
V
EN
+0.8V
t and t ≤ 100ns
S
r
f
-5V
1b
t
t
EN(ON)
EN(OFF)
A
A
ALL
OTHERS
1
0V
0.1V
0
O
IH6208
SWITCH
OUTPUT
S
EN
4b
V
OUT
(SEE FIGURE 1)
V
D
V
OUT
2
EN
200Ω
35pF
0.9V
O
GND
V
-15V
O
-5V
FIGURE 3. t
ON
AND t
SWITCHING TEST CIRCUIT AND WAVEFORMS
OFF
IH6208 Application Information
ENABLE Input Strobing Levels
Using the IH6208 with Supplies Other Than ±15V
The ENABLE input on the IH6208 requires a minimum of The IH6208 can be used with power supplies ranging from
+4.5V to trigger to the “1” state and a maximum of +0.8V to ±6V to ±16V. The switch r will increase as the supply
DS(ON)
trigger to the “0” state. If the ENABLE input is being driven voltages decrease, however, the multiplexer error term (the
from TTL logic, a pull-up resistor of 1kΩ to 3kΩ is required product of leakage times r ) will remain approximately
DS(ON)
from the gate output to +5V supply. (See Figure 4)
constant since leakage decreases as the supply voltages
are reduced.
When the EN in put is driven from CMOS logic, no pullup is
necessary, see Figure 5.
Caution must be taken to ensure that the enable (EN)
voltage is at least 0.7V below V+ at all times. If this is not
done, the Address input strobing levels will not function
properly. This may be achieved quite simply by connecting
EN (pin 2) to V+ (pin 14) via a silicon diode as shown in
Figure 6. When using this type of configuration, a further
requirement must be met: the strobe levels of A0 and A1
must be within 2.5V of the EN voltage in order to define a
binary “1” state. For the case shown in Figure 6 the EN
voltage is 11.3V which means that logic high at A0 and A1 is
+8.8V (logic low continues to be 0.8V). In this configuration
the IH6208 cannot be driven by TTL (+5V) or CMOS (+5V)
logic. It can be driven by TTL open collector logic or CMOS
logic with +12V supplies.
The supply voltage of the CD4009 affects the switching
speed of the IH6208; the same is true for TTL supply voltage
levels. The following chart shows the effect, on t
supply varying from +4.5V to +5.5V.
for a
trans
CMOS OR TTL
SUPPLY VOLTAGE
TYPICAL T
TRANS
o
AT 25 C
400ns
300ns
250ns
200ns
175ns
+4.5V
+4.75V
+5.00V
+5.25V
+5.50V
The throughput rate can therefore be maximized by using a
+5V to +5.5V supply for the ENABLE Strobe Logic.
If the logic and the IH6208 have common supplies, the EN
pin should again be connected to the supply through a
The examples shown in Figure 4 and 5 deal with ENABLE silicon diode. In this case, tying EN to the logic supply
strobing when expansion to more than eight channels is directly will not work since it violates the 0.7V differential
required. In these cases the EN terminal acts as a fourth voltage required between V+ and EN, (See Figure 7). A 1µF
address input. If eight channels or less are being capacitor can be placed across the diode to minimize
multiplexed, the EN terminal can be directly connected to switching glitches.
+5V logic supply to enable the IH6208 at all times.
12-132
HARRIS [ HARRIS CORPORATION ]
