MAX378 [MAXIM]
High-Voltage, Fault-Protected Analog Multiplexers; 高电压，故障保护模拟多路复用器
| 型号： | MAX378 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | High-Voltage, Fault-Protected Analog Multiplexers |
| 文件： | 总12页 (文件大小：106K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1902; Rev 1; 8/94
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
8/MAX379
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ Fault Input Voltage ±75V with Power Supplies Off
♦ Fault Input Voltage ±60V with ±15V Power Supplies
♦ All Switches Off with Power Supplies Off
The MAX378 8-channel single-ended (1-of-8) multiplexer
and the MAX379 4-channel differential (2-of-8) multiplexer
use a series N-channel/P-channel/N-channel structure to
provide significant fault protection. If the power supplies to
the MAX378/MAX379 are inadvertently turned off while
input voltages are still applied, all channels in the muxes
are turned off, and only a few nanoamperes of leakage cur-
rent will flow into the inputs. This protects not only the
MAX378/MAX379 and the circuitry they drive, but also the
sensors or signal sources that drive the muxes.
♦ On Channel Turns OFF if Overvoltage Occurs on
Input or Output
♦ Only Nanoamperes of Input Current Under All
Fault Conditions
♦ No Increase in Supply Currents Due to Fault
Conditions
♦ Latchup-Proof Construction
The series N-channel/P-channel/N-channel protection
structure has two significant advantages over the simple
current-limiting protection scheme of the industry’s first-
generation fault-protected muxes. First, the Maxim protec-
tion scheme limits fault currents to nanoamp leakage
values rather than many milliamperes. This prevents dam-
age to sensors or other sensitive signal sources. Second,
the MAX378/MAX379 fault-protected muxes can withstand
a continuous ±60V input, unlike the first generation, which
had a continuous ±35V input limitation imposed by power
dissipation considerations.
♦ Operates from ±4.5V to ±18V Supplies
♦ All Digital Inputs are TTL and CMOS Compatible
♦ Low-Power Monolithic CMOS Design
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
16 Plastic DIP
24 Wide SO
16 CERDIP
Dice**
MAX378CPE
MAX378CWG
MAX378CJE
MAX378C/D
MAX378EPE
MAX378EWG
MAX378EJE
MAX378MJE
MAX378MLP
0°C to +70°C
All digital inputs have logic thresholds of 0.8V and 2.4V,
ensuring both TTL and CMOS compatibility without requir-
ing pull-up resistors. Break-before-make operation is
guaranteed. Power dissipation is less than 2mW.
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
-55°C to +125°C
16 Plastic DIP
24 Wide SO
16 CERDIP
16 CERDIP
20 LCC*
________________________Ap p lic a t io n s
Data Acquisition Systems
Industrial and Process Control Systems
Avionics Test Equipment
Ordering Information continued at end of data sheet.
* Contact factory for availability.
**The substrate may be allowed to float or be tied to V+ (JI CMOS).
Signal Routing Between Systems
__________________________________________________________P in Co n fig u ra t io n s
TOP VIEW
A0
EN
V-
1
2
3
4
5
6
7
8
A0
EN
1
2
3
4
5
6
7
8
A1
A1
16
16
15 A2
15 GND
14 V+
V-
14 GND
13 V+
IN1
IN1A
MAX378
MAX379
13 IN1B
IN2
IN3
IN2A
IN3A
IN4A
OUTA
12
11
10
9
12
11
10
9
IN5
IN6
IN7
IN8
IN2B
IN3B
IN4B
OUTB
IN4
OUT
DIP
DIP
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
Ca ll t o ll fre e 1 -8 0 0 -9 9 8 -8 8 0 0 fo r fre e s a m p le s o r lit e ra t u re .
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
ABSOLUTE MAXIMUM RATINGS
Voltage between Supply Pins ..............................................+44V
V+ to Ground ...................................................................+22V
V- to Ground......................................................................-22V
Digital Input Overvoltage:
Continuous Current, IN or OUT...........................................20mA
Peak Current, IN or OUT
(Pulsed at 1ms, 10% duty cycle max) ............................40mA
Power Dissipation (Note 1) (CERDIP) ................................1.28W
Operating Temperature Range:
MAX378/379C .....................................................0°C to +70°C
MAX378/379E ..................................................-40°C to +85°C
MAX378/379M ...............................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
V+ ......................................................................+4V
V- ........................................................................-4V
Analog Input with Multiplexer Power On..............................±65V
V , V
EN A
{
Recommended
Power Supplies
V+ .....................................+15V
V- .......................................-15V
{
}
Analog Input with Multiplexer Power Off..............................±80V
Note 1: Derate 12.8mW/°C above T = +75°C
A
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V+ = +15V, V- = -15V; V (Logic Level High) = +2.4V, V (Logic Level Low) = +0.8V, unless otherwise noted.)
AH
AL
8/MAX379
0°C to +70°C
and
-40°C to +85°C
-55°C to +125°C
PARAMETER
SYMBOL
CONDITIONS
TEMP
UNITS
MIN TYP MAX MIN TYP MAX
STATIC
ON Resistance
+25°C
Full
2.0
3.0
3.0
4.0
2.0
3.0
3.5
4.0
V
V
AL
= ±10V, I = 100µA
IN
= 0.8V, V = 2.4V
AH
OUT
r
kΩ
DS(ON)
±
+25°C -0.5 0.03 0.5
-1.0 0.03 1.0
V
IN
= ±10V, V
=
10V
OUT
OFF Input Leakage Current
OFF Output Leakage Current
I
nA
IN(OFF)
V
= 0.8V (Note 6)
EN
Full
-50
50
-50
50
2.0
±
+25°C -1.0 0.1
1.0
-2.0 0.1
V
= ±10V, V
=
10V
MAX378
MAX379
OUT
IN
I
V
= 0.8V
Full
Full
-200
-100
200 -200
100 -100
200
100
20
nA
nA
OUT(OFF)
EN
(Note 6)
+25°C -10 0.1
10
-20 0.1
V
= V
= ±10V
IN(ALL)
OUT
ON Channel Leakage Current
Analog Signal Range
I
V
= V = 2.4V
= 0.8V (Note 5)
MAX378
MAX379
Full
Full
Full
-600
-300
-15
600 -600
300 -300
600
300
+15
OUT(ON)
AH EN
V
AL
V
AN
(Note 2)
+15
-15
V
Differential OFF Output
Leakage Current
MAX379 only
(Note 6)
I
Full
-50
50
-50
50
nA
DIFF
FAULT
+25°C
Full
20
20
nA
µA
Output Leakage Current
(with Input Overvoltage)
V
= 0V, V = ±60V
OUT IN
I
OUT(OFF)
(Notes 3, 4)
10
25
20
40
Input Leakage Current
(with Overvoltage)
V
= ±60V, V = ±10V
OUT
IN
I
+25°C
+25°C
µA
µA
IN(OFF)
(Notes 3, 4)
Input Leakage Current
(with Power Supplies Off)
V
= ±75V, V = V
= 0V
OUT
IN
EN
I
10
0.8
1.0
20
0.8
1.0
IN(OFF)
A = A = A = 0V or 5V
0 1 2
CONTROL
Input Low Threshold
Input High Threshold
V
AL
(Note 4)
(Note 4)
Full
Full
V
V
V
AH
2.4
2.4
Input Leakage Current
(High or Low)
I
A
V
A
= 5V or 0V (Note 5)
Full
-1.0
-1.0
µA
2
_______________________________________________________________________________________
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
8/MAX379
ELECTRICAL CHARACTERISTICS (continued)
(V+ = +15V, V- = -15V; V (Logic Level High) = +2.4V, V (Logic Level Low) = +0.8V, unless otherwise noted.)
AH
AL
0°C to +70°C
and
-40°C to +85°C
-55°C to +125°C
PARAMETER
SYMBOL
CONDITIONS
TEMP
UNITS
MIN TYP MAX MIN TYP MAX
DYNAMIC
Access Time
t
Figure 1
V = +5V, V = ±10V
EN
+25°C
+25°C
0.5
1.0
0.5
1.0
µs
ns
A
Break-Before-Make Delay
(Figure 2)
IN
t
-t
25 200
25 200
ON OFF
A , A , A strobed
0
1
2
+25°C
Full
400 750
1000
400 1000
1500
300
Enable Delay (ON)
Enable Delay (OFF)
t
Figure 3
Figure 3
ns
ns
µs
ON(EN)
+25°C
Full
300 500
1000
t
OFF(EN)
1000
1.2
1.2
Settling Time (0.1%)
(0.01%)
t
+25°C
SETT
3.5
3.5
V
= 0.8V, R = 1kΩ, C = 15pF
EN
L
L
“OFF Isolation”
OFF
+25°C
+25°C
+25°C
50
68
50
68
dB
pF
pF
(ISO)
V = 7V
, f = 100kHz
RMS
Channel Input Capacitance
Channel Output Capacitance
C
5
5
IN(OFF)
25
12
25
12
MAX378
MAX379
C
OUT(OFF)
Digital Input Capacitance
C
+25°C
+25°C
5
5
pF
pF
A
Input to Output Capacitance
SUPPLY
C
0.1
0.1
DS(OFF)
+25°C
Full
0.1
0.3
0.6
0.7
0.2
0.5
1.0
1.0
V
= 0.8V or 2.4V
EN
Positive Supply Current
I+
I-
mA
mA
V
All V = 0V or 5V
A
+25°C
Full
0.01 0.1
0.02 0.2
0.01 0.1
0.02 0.1
V
= 0.8V or 2.4V
EN
Negative Supply Current
All V = 0V or 5V
A
Power-Supply Range for
Continuous Operation
V
OP
(Note 7)
+25°C ±4.5
±18 ±4.5
±18
Note 2: When the analog signal exceeds +13.5V or -12V, the blocking action of Maxim’s gate structure goes into operation. Only
leakage currents flow and the channel ON resistance rises to infinity.
Note 3: The value shown is the steady-state value. The transient leakage is typically 50µA. See Detailed Description.
Note 4: Guaranteed by other static parameters.
Note 5: Digital input leakage is primarily due to the clamp diodes. Typical leakage is less than 1nA at +25°C.
Note 6: Leakage currents not tested at T = cold temp.
A
Note 7: Electrical characteristics, such as ON Resistance, will change when power supplies other than ±15V are used.
_______________________________________________________________________________________
3
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
INPUT LEAKAGE vs.
INPUT VOLTAGE WITH V+ = V- = 0V
OFF CHANNEL LEAKAGE CURRENT vs.
INPUT VOLTAGE WITH ±15V SUPPLIES
OUTPUT LEAKAGE CURRENT vs. OFF CHANNEL
OVERVOLTAGE WITH ±15V SUPPLIES
10n
1m
100µ
10µ
100µ
10µ
1µ
1µ
1n
100n
OPERATING
RANGE
OPERATING
RANGE
OPERATING
RANGE
100n
10n
10n
1n
100p
1n
100p
10p
10p
1p
100p
10p
1p
8/MAX379
-100
-50
0
50
100
-120
-60
0
60
120
-120
-60
0
60
120
V
IN
(V)
V (V)
IN
V
IN(OFF)
(V)
DRAIN-SOURCE ON-RESISTANCE vs.
ANALOG INPUT VOLTAGE
7
6
5
4
3
2
+3.5V
+4V
+13V
±5V
SUPPLIES
+13V
±15V
SUPPLIES
NOTE: Typical R
match @ +10V
DS(ON)
1
0
Analog in (±15V supplies) = 2%
for lowe s t to hig he s t R
DS(ON)
c ha nne l; @ -10V Ana log in,
match = 3%.
-15 -10
-5
0
5
10
15
20
ANALOG INPUT (V)
A2
ADDRESS
MAX378: V = 3.0V
AH
IN1
IN2
DRIVE (V )
A
±10V
50%
MAX378
GND
IN2-IN7
A1
A0
EN
0V
±
PROBE
V
A
10V
IN8
+V
50Ω
AH
+10V
OUT
OUTPUT A
-10V
10M
14pF
90%
t
A
Figure 1. Access Time vs. Logic Level (High)
_______________________________________________________________________________________
4
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
8/MAX379
A2
MAX358: V = 3.0V
AH
+5V
IN1
IN2
ADDRESS
MAX378*
IN2-IN7
IN8
A1
A0
EN
DRIVE (V )
0V
A
V
A
V
OUT
2.4V
OUT
50Ω
OUTPUT
50%
50%
GND
12.5pF
1k
t
OPEN
*SIMILAR CONNECTION FOR MAX379
Figure 2. Break-Before-Make Delay (t
)
OPEN
+10V
IN1
A2
MAX378: V = 3.0V
AH
ENABLE DRIVE
50%
MAX378*
GND
IN2-IN7
OUT
A1
A0
EN
0V
90%
V
A
OUTPUT
90%
12.5pF
1k
50Ω
t
ON(EN)
t
OFF(EN)
*SIMILAR CONNECTION FOR MAX379
Figure 3. Enable Delay (t
, t
)
ON(EN) OFF(EN)
+5V
+15V
0V
V-
V-
A0
A0
+5V
A1
A1
A2
or
A2
0V
MAX378
MAX378
EN
EN
I
OUT
IN1
I
OUT
IN1
IN8
10k
±75V
10k
±60V
V
V-
GND
V-
GND
±10V
ANALOG
SIGNAL
0V
-15V
Figure 4. Input Leakage Current (Overvoltage)
Figure 5. Input Leakage Current (with Power Supplies OFF)
_______________________________________________________________________________________
5
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
Truth Table—MAX378
Truth Table—MAX379
ON
SWITCH
ON
SWITCH
A2
A1
A0
EN
A1
A0
EN
X
0
0
0
0
1
1
1
1
X
0
0
1
1
0
0
1
1
X
0
1
0
1
0
1
0
1
0
1
1
1
1
1
1
1
1
NONE
X
0
0
1
1
X
0
1
0
1
0
1
1
1
1
NONE
1
2
3
4
5
6
7
8
1
2
3
4
Note: Logic “0” = V ≤ 0.8V, Logic “1” = V ≥ 2.4V
AL
AH
+15V
V+
8/MAX379
THERMOCOUPLE
STRAIN GUAGE
+15V
IN1
OUT
IN2
IN3
MAX420
4-20mA LOOP
TRANSMITTER
-15V
1M
+15V
V+
MAX378
IN4
IN5
IN6
IN7
IN8
IN1
IN2
IN3
IN4
IN5
100k
10k
+10V
GAIN REFERENCE
DG508A
MAX358
OR
OUT
ZERO REFERENCE
V-
-15V
GND
1k
MAX378
V-
-15V
GND
111Ω
Figure 6. Typical Data Acquisition Front End
In systems with fewer than eight inputs, an unused chan-
nel can be connected to the system ground reference
point for software zero correction. A second channel
connected to the system voltage reference allows gain
correction of the entire data acquisition system as well.
_______________Typ ic a l Ap p lic a t io n s
Fig ure 6 s hows a typ ic a l d a ta a c q uis ition s ys te m
using the MAX378 multiplexer. Since the multiplexer
is driving a high-impedance input, its error is a func-
tion of its own resistance (R
) times the multi-
DS(ON)
A MAX420 precision op amp is connected as a pro-
grammable-gain amplifier, with gains ranging from 1 to
10,000. The guaranteed 5µV unadjusted offset of the
MAX420 maintains high signal accuracy, while program-
mable gain allows the output signal level to be scaled to
the optimum range for the remainder of the data acqui-
sition system, normally a Sample/Hold and A/D. Since
the gain-changing multiplexer is not connected to the
external sensors, it can be either a DG508A multiplexer
or the fault-protected MAX358 or MAX378.
plexer leakage current (I
) and the amplifier
OUT(ON)
bias current (I
):
BIAS
V
ERR
= R
x (I
+ I
BIAS
(MAX420))
DS(ON)
OUT(ON)
= 2.0kΩ x (2nA + 30pA)
= 18.0µV maximum error
In most cases, this error is low enough that preamplifi-
cation of input signals is not needed, even with very
low-level signals such as 40µV/°C from type J thermo-
couples.
6
_______________________________________________________________________________________
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
8/MAX379
Input switching, however, must be done with a fault-
protected MAX378 multiplexer, to provide the level of
protection and isolation required with most data acqui-
sition inputs. Since external signal sources may contin-
ue to supply voltage when the multiplexer and system
power are turned off, non-fault-protected multiplexers,
or even first-generation fault-protected devices, will
allow many milliamps of fault current to flow from out-
side sources into the multiplexer. This could result in
damage to either the sensors or the multiplexer. A non-
fault-protected multiplexer will also allow input overvolt-
a g e s to a p p e a r a t its outp ut, p e rha p s d a ma g ing
Sample/Holds or A/Ds. Such input overdrives may also
cause input-to-input shorts, allowing the high current
output of one sensor to possibly damage another.
Q
Q
Q
3
1
2
+60V
OVERVOLTAGE
S
S
D
S
D
D
N-CHANNEL MOSFET
IS TURNED OFF
G
G
G
BECAUSE V = -60V
GS
The MAX378 eliminates all of the above problems. It
not only limits its output voltage to safe levels, with or
without power applied (V+ and V-), but also turns all
channels off when power is removed. This allows it to
draw only sub-microamp fault currents from the inputs,
and maintain isolation between inputs for continuous
input levels up to ±75V with power supplies off.
Figure 8. +60V Overvoltage with Multiplexer Power OFF
-15V
+15V
-15V
+60V FORCED
ON COMMON
OUTPUT
LINE BY
EXTERNAL
CIRCUITRY
_______________De t a ile d De s c rip t io n
Q
Q
Q
3
-60V
1
2
Fa u lt P ro t e c t io n Circ u it ry
The MAX378/MAX379 are fully fault protected for contin-
uous input voltages up to ±60V, whether or not the V+
and V- power supplies are present. These devices use
a “series FET” switching scheme which not only pro-
tects the multiplexer output from overvoltage, but also
limits the input current to sub-microamp levels.
-60V
OVERVOLTAGE
N-CHANNEL MOSFET
IS TURNED OFF
+15V FROM
DRIVERS
N-CHANNEL
MOSFET IS OFF
-15V FROM
DRIVERS
BECAUSE V = +45V
GS
P-CHANNEL
MOSFET IS OFF
Figures 7 and 8 show how the series FET circuit pro-
tects against overvoltage conditions. When power is
off, the gates of all three FETs are at ground. With a -60V
input, N-channel FET Q1 is turned on by the +60V gate-
Figure 9. -60V Overvoltage on an OFF Channel with
Multiplexer Power Supply ON
-15V
+15V
-15V
Q
1
Q
2
Q
3
-60V
S
Q
1
Q
2
Q
3
+13.5V
-60V
OVERVOLTAGE
+60V
OVERVOLTAGE
+13.5V
OUTPUT
S
D
S
D
D
N-CHANNEL MOSFET
IS TURNED ON
V
TN = +1.5V
N-CHANNEL MOSFET
IS TURNED ON
G
G
G
BECAUSE V = +60V
GS
-15V FROM
DRIVERS
N-CHANNEL
MOSFET IS ON
+15V FROM
DRIVERS
BECAUSE V = -45V
GS
P-CHANNEL
MOSFET IS OFF
Figure 7. -60V Overvoltage with Multiplexer Power OFF
_______________________________________________________________________________________
Figure 10. +60V Overvoltage Input to the ON Channel
7
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
to-source voltage. The P-channel device (Q2), howev-
ly connected to the output. In a typical data acquisition
er, has +60V V and is turned off, thereby preventing
the input signal from reaching the output. If the input
system, such as in Figure 6, the dominant delay is not the
switching time of the MAX378 multiplexer, but is the set-
tling time of the following amplifiers and S/H. Another limit-
ing factor is the RC time constant of the multiplexer
GS
voltage is +60V, Q1 has a negative V , which turns it
GS
off. Similarly, only sub-microamp leakage currents can
flow from the output back to the input, since any volt-
age will turn off either Q1 or Q2.
R
plus the signal source impedance multiplied by
DS(ON)
the load capacitance on the output of the multiplexer.
Even with low signal source impedances, 100pF of capac-
itance on the multiplexer output will approximately double
the settling time to 0.01% accuracy.
Figure 9 shows the condition of an OFF channel with
V+ and V- present. As with Figures 7 and 8, either an
N-channel or a P-channel device will be off for any
input voltage from -60V to +60V. The leakage current
with negative overvoltages will immediately drop to a
few nanoamps at +25°C. For positive overvoltages,
that fault current will initially be 40µA or 50µA, decaying
over a few seconds to the nanoamp level. The time
constant of this decay is caused by the discharge of
stored charge from internal nodes, and does not com-
promise the fault-protection scheme.
Op e ra t io n w it h S u p p ly Vo lt a g e
Ot h e r t h a n ±1 5 V
The main effect of supply voltages other than ±15V is
the reduction in output signal range. The MAX378 limits
the output voltage to about 1.5V below V+ and about 3V
above V-. In other words, the output swing is limited to
+3.5V to -2V when operating from ±5V. The Typical
8/MAX379
Operating Characteristics graphs show typical R
,
DS(ON)
Figure 10 shows the condition of the ON channel with
V+ and V- present. With input voltages less than ±10V,
all three FETs are on and the input signal appears at the
output. If the input voltage exceeds V+ minus the N-
for ±15V, ±10V, and ±5V power supplies. Maxim tests
and guarantees the MAX378/MAX379 for operation from
±4.5V to ±18V supplies. The switching delays are
increased by about a factor of 2 at ±5V, but break-
before-make action is preserved.
channel threshold voltage (V ), then the N-channel
TN
FET will turn off. For voltages more negative than V-
The MAX378/MAX379 can be operated with a single +9V
to +22V supply, as well as asymmetrical power supplies
such as +15V and -5V. The digital threshold will remain
approximately 1.6V above GND and the analog character-
minus the P-channel threshold (V ), the P-channel
TP
device will turn off. Since V is typically 1.5V and V
TN
TP
is typically 3V, the multiplexer’s output swing is limited
to about -12V to +13.5V with ±15V supplies.
istics such as R
are determined by the total voltage
DS(ON)
The Typical Operating Characteristics graphs show typi-
cal leakage vs. input voltage curves. Although the max-
imum ra te d inp ut of the s e d e vic e s is ± 65V, the
MAX378/MAX379 typically have excellent performance
up to ±75V, providing additional margin for the unknown
transients that exist in the real world. In summary, the
MAX378/MAX379 provide superior protection from all
fault conditions while using a standard, readily pro-
duced junction-isolated CMOS process.
difference between V+ and V-. Connect V- to 0V when
operating with a +9V to +22V single supply.
This means that the MAX378/MAX379 will operate with
standard TTL-logic levels, even with ±5V power sup-
plies. In all cases, the threshold of the EN pin is the
same as the other logic inputs.
Table 1a. MAX378 Charge Injection
Supply Voltage Analog Input Level Injected Charge
S w it c h in g Ch a ra c t e ris t ic s
a n d Ch a rg e In je c t io n
+1.7V
0V
-1.7V
+100pC
+70pC
+45pC
±5V
Ta b le 1 s hows typ ic a l c ha rg e -inje c tion le ve ls vs .
power-supply voltages and analog input voltage. Note
that since the channels are well matched, the differen-
tial charge injection for the MAX379 is typically less
than 5pC. The charge injection that occurs during
switching creates a voltage transient whose magnitude
is inversely proportional to the capacitance on the mul-
tiplexer output.
+5V
0V
-5V
+200pC
+130pC
+60pC
±10V
+10V
0V
-10V
+500pC
+180pC
+50pC
±15V
Test Conditions:
C = 1000pF on multiplexer output; the tabu-
L
The channel-to-channel switching time is typically 600ns,
with about 200ns of break-before-make delay. This 200ns
break-before-make delay prevents the input-to-input short
that would occur if two input channels were simultaneous-
lated analog input level is applied to channel 1; channels 2
through 8 are open circuited. EN = +5V, A1 = A2 = 0V, A0 is
toggled at 2kHz rate between 0V and 3V. +100pC of charge
creates a +100mV step when injected into a 1000pF load
capacitance.
8
_______________________________________________________________________________________
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
8/MAX379
rents as the off-channel input voltages are varied. The
Table 1b. MAX379 Charge Injection
MAX378 output leakage varies only a few picoamps as
all seven off inputs are toggled from -10V to +10V. The
output voltage change depends on the impedance level
Injected Charge
Supply
Analog
Differential
Voltage Input Level
Out A
Out B
A-B
at the MAX378 output, which is R
plus the input
DS(ON)
signal source resistance in most cases, since the load
driven by the MAX378 is usually a high impedance. For
a signal source impedance of 10kΩ or lower, the DC
crosstalk exceeds 120dB.
+1.7V
0V
-1.7V
+105pC
+73pC
+48pC
+107pC
+74pC
+50pC
-2pC
-1pC
-2pC
±5V
±10V
±15V
+5V
0V
-5V
+215pC
+135pC
+62pC
+220pC
+139pC
+63pC
-5pC
-4pC
-1pC
Table 2 shows typical AC crosstalk and off-isolation per-
formance. Digital feedthrough is masked by the analog
charge injection when the output is enabled. When the
output is disabled, the digital feedthrough is virtually
unmeasurable, since the digital pins are physically iso-
lated from the analog section by the GND and V- pins.
The ground plane formed by these lines is continued
onto the MAX378/MAX379 die to provide over 100dB
isolation between the digital and analog sections.
+10V
0V
-10V
+525pC
+180pC
+55pC
+530pC
+185pC
+55pC
-5pC
-5pC
0pC
Test Conditions: C = 1000pF on Out A and Out B; the tabulat-
L
ed analog input level is applied to inputs 1A and 1B; channels
2 through 4 are open circuited. EN = +5V, A1 = 0V, A0 is tog-
gled from 0V to 3V at a 2kHz rate.
Dig it a l In t e rfa c e Le ve ls
The typical digital threshold of both the address lines
and the EN pin is 1.6V, with a temperature coefficient of
about -3mV/°C. This ensures compatibility with 0.8V to
2.4V TTL-log ic s wing s ove r the e ntire te mp e ra ture
range. The digital threshold is relatively independent of
the supply voltages, moving from 1.6V typical to 1.5V
typical as the power supplies are reduced from ±15V to
±5V. In all cases, the digital threshold is referenced to
GND.
Table 2a. Typical Off-Isolation
Rejection Ratio
Frequency
One Channel Driven
All Channels Driven
100kHz
74dB
64dB
500kHz
72dB
48dB
1MHz
66dB
44dB
Test Conditions:
V
IN
= 20V
at the tabulated frequency,
P-P
The digital inputs can also be driven with CMOS-logic
levels swinging from either V+ to V- or from V+ to GND.
The digital input current is just a few nanoamps of leak-
age at all input voltage levels, with a guaranteed maxi-
mum of 1µA. The digital inputs are protected from ESD
by a 30V zener diode between the input and V+, and
can be driven ±4V beyond the supplies without drawing
excessive current.
R
L
= 1.5kΩ between OUT and GND, EN = 0V.
20V
P-P
OIRR = 20 Log ____________
V
OUT (P-P)
Table 2b. Typical Crosstalk
Rejection Ratio
Op e ra t io n a s a De m u lt ip le x e r
The MAX378/MAX379 will function as a demultiplexer,
where the input is applied to the OUT pin, and the input
pins are used as outputs. The MAX378/MAX379 pro-
vide both break-before-make action and full fault protec-
tion when operated as a demultiplexer, unlike earlier
generations of fault-protected multiplexers.
Frequency
100kHz
70dB
62dB
500kHz
68dB
46dB
1MHz
64dB
42dB
F
L
= 1.5k
= 10k
R
L
Test Conditions: Specified R connected from OUT to GND,
L
Ch a n n e l-t o -Ch a n n e l Cro s s t a lk ,
Off Is o la t io n , a n d Dig it a l Fe e d t h ro u g h
At DC a nd low fre q ue nc ie s , c ha nne l-to-c ha nne l
crosstalk is caused by variations in output leakage cur-
EN = +5V, A0 = A1 = A2 = +5V (Channel 1 selected). 20V
P-P
at the tabulated frequency is applied to Channel 2. All other
channels are open circuited. Similar crosstalk rejection can be
observed between any two channels.
_______________________________________________________________________________________
9
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
_____________________________________________P in Co n fig u ra t io n s (c o n t in u e d )
TOP VIEW
A0
EN
A1
A0
EN
A1
1
2
24
23
22
21
20
19
18
17
16
15
14
1
2
24
23
22
21
20
19
18
17
16
15
14
13
A2
N.C.
GND
N.C.
V+
N.C.
N.C.
N.C.
N.C.
GND
N.C.
V+
3
3
4
4
MAX378
V-
IN1
IN2
IN3
MAX379
V-
IN1A
IN2A
IN3A
5
5
8/MAX379
IN5
IN6
N.C.
IN7
N.C.
N.C.
6
IN1B
IN2B
IN3B
IN4B
N.C.
N.C.
OUTB
6
7
7
8
8
IN4
N.C.
N.C.
OUT
IN4A
N.C.
9
9
10
11
12
10
11
12
N.C.
OUTA
13 IN8
SO
SO
V- 4
IN1 5
N.C. 6
IN2 7
IN3 8
18
17
16
15
14
V- 4
IN1A 5
N.C. 6
IN2A 7
IN3A 8
18
V+
GND
V+
17
16
15
14
IN1B
N.C.
IN2B
IN3B
N.C.
IN5
IN6
MAX378
MAX379
LCC
LCC
10 ______________________________________________________________________________________
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
8/MAX379
_Ord e rin g In fo rm a t io n (c o n t in u e d )
_________________Ch ip To p o g ra p h ie s
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
16 Plastic DIP
24 Wide SO
16 CERDIP
Dice**
MAX378
MAX379CPE
MAX379CWG
MAX379CJE
MAX379C/D
MAX379EPE
MAX379EWG
MAX379EJE
MAX379MJE
MAX379MLP
IN8 OUT
IN4
0°C to +70°C
0°C to +70°C
IN7
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
-55°C to +125°C
16 Plastic DIP
24 Wide SO
16 CERDIP
16 CERDIP
20 LCC*
IN7
IN6
IN3
IN2
0. 229"
(5. 816mm)
* Contact factory for availability.
**The substrate may be allowed to float or be tied to V+ (JI CMOS).
IN5
V+
IN1
V-
GND
A0
A2
A1
EN
0. 151"
(3. 835mm)
NOTE: Connect substrate to V+ or leave it floating.
MAX379
OUTB OUTA
IN4A
IN4B
IN3B
IN2B
IN3A
0. 229"
(5. 816mm)
IN2A
IN1B
V+
IN1A
V-
GND
A0
A1
EN
0. 151"
(3. 835mm)
NOTE: Connect substrate to V+ or leave it floating.
______________________________________________________________________________________ 11
Hig h -Vo lt a g e , Fa u lt -P ro t e c t e d
An a lo g Mu lt ip le x e rs
________________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
MIN
0.093
MAX
0.104
0.012
0.019
0.013
0.299
MIN
2.35
0.10
0.35
0.23
7.40
MAX
2.65
0.30
0.49
0.32
7.60
D
A
A1 0.004
0°- 8°
B
C
E
e
0.014
0.009
0.291
A
0.101mm
0.004in.
1.27
0.050
e
B
A1
H
L
0.394
0.016
0.419
0.050
10.00
0.40
10.65
1.27
C
L
8/MAX379
INCHES
MILLIMETERS
MAX
PINS
DIM
MIN MAX MIN
E
H
Wide SO
SMALL-OUTLINE
PACKAGE
0.398 0.413 10.10 10.50
0.447 0.463 11.35 11.75
0.496 0.512 12.60 13.00
0.598 0.614 15.20 15.60
D
D
D
D
D
16
18
20
24
28
(0.300 in.)
0.697 0.713 17.70 18.10
21-0042A
INCHES
MILLIMETERS
DIM
D1
MIN
MAX
0.200
–
MIN
–
MAX
5.08
–
A
–
A1 0.015
A2 0.125
A3 0.055
0.38
3.18
1.40
0.41
1.27
0.20
18.92
0.13
7.62
6.10
0.150
0.080
0.022
0.065
0.012
0.765
0.030
0.325
0.280
3.81
2.03
0.56
1.65
0.30
19.43
0.76
8.26
7.11
B
0.016
B1 0.050
C
D
0.008
0.745
E
D1 0.005
0.300
E1 0.240
E
E1
D
e
0.100 BSC
0.300 BSC
2.54 BSC
7.62 BSC
A3
e
A
B
A2
A1
A
L
e
–
0.115
0˚
0.400
0.150
15˚
–
10.16
3.81
L
2.92
0˚
α
15˚
21-587A
α
16-PIN PLASTIC
DUAL-IN-LINE
PACKAGE
C
e
B1
e
e
A
B
B
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 __________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0
© 1994 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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