AD790JR-REEL ,Fast, Precision ComparatorCHARACTERISTICS2Offset Voltage 0.45 1.5 0.35 0.6 0.45 1.5 mVT to T 2.0 0.85 2.0 mVMIN MAX3T to T 0. ..
AD790JRZ , Fast, Precision Comparator
AD790KN ,Fast, Precision ComparatorCHARACTERISTICS10.2 1.0 0.05 0.25 0.2 1.0 mVOffset VoltageT to T 1.5 0.5 1.5 mVMIN MAX2Hysteresis T ..
AD790SQ ,Fast, Precision ComparatorCHARACTERISTICS4Supply Voltage T to T 4.5 7 4.5 7 4.7 7 VMIN MAXQuiescent Current 10 12 10 12 10 12 ..
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ADM6315-29D4ARTZR7 , Open-Drain Microprocessor Supervisory Circuit in 4-Lead SOT-143
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AD790AQ-AD790JN-AD790JR-AD790JR-REEL-AD790KN-AD790SQ
Fast, Precision Comparator
REV.B
Fast, Precision
Comparator
FEATURES
45 ns max Propagation Delay
Single +5 V or Dual 615 V Supply Operation
CMOS or TTL Compatible Output
250 mV max Input Offset Voltage
500 mV max Input Hysteresis Voltage
15 V max Differential Input Voltage
Onboard Latch
60 mW Power Dissipation
Available in 8-Pin Plastic and Hermetic Cerdip
Packages
MIL-STD-883B Processing Available
Available in Tape and Reel in Accordance with
EIA-481A Standard
APPLICATIONS
Zero-Crossing Detectors
Overvoltage Detectors
Pulse-Width Modulators
Precision Rectifiers
Discrete A/D Converters
Delta-Sigma Modulator A/Ds
PRODUCT DESCRIPTIONThe AD790 is a fast (45 ns), precise voltage comparator, with a
number of features that make it exceptionally versatile and easy
to use. The AD790 may operate from either a single +5 V sup-
ply or a dual ±15 V supply. In the single-supply mode, the
AD790’s inputs may be referred to ground, a feature not found
in other comparators. In the dual-supply mode it has the unique
ability of handling a maximum differential voltage of 15 V across
its input terminals, easing their interfacing to large amplitude
and dynamic signals.
This device is fabricated using Analog Devices’ Complementary
Bipolar (CB) process–which gives the AD790’s combination of
fast response time and outstanding input voltage resolution
(1 mV max). To preserve its speed and accuracy, the AD790
incorporates a “low glitch” output stage that does not exhibit
the large current spikes normally found in TTL or CMOS out-
put stages. Its controlled switching reduces power supply distur-
bances that can feed back to the input and cause undesired
oscillations. The AD790 also has a latching function which makes
it suitable for applications requiring synchronous operation.
The AD790 is available in five performance grades. The AD790J
and the AD790K are rated over the commercial temperature
range of 0°C to +70°C. The AD790A and AD790B are rated
over the industrial temperature range of –40°C to +85°C. The
AD790S is rated over the military temperature range of –55°C to
+125°C and is available processed to MIL-STD-883B, Rev. C.
PRODUCT HIGHLIGHTSThe AD790’s combination of speed, precision, versatility
and low cost makes it suitable as a general purpose compara-
tor in analog signal processing and data acquisition systems.Built-in hysteresis and a low-glitch output stage minimize the
chance of unwanted oscillations, making the AD790 easier to
use than standard open-loop comparators.The hysteresis combined with a wide input voltage range
enables the AD790 to respond to both slow, low level (e.g.,
10 mV) signals and fast, large amplitude (e.g., 10 V) signals.A wide variety of supply voltages are acceptable for operation
of the AD790, ranging from single +5 V to dual +5 V/–12 V,5 V, or +5 V/±15 V supplies.The AD790’s power dissipation is the lowest of any compara-
tor in its speed range.The AD790’s output swing is symmetric between VLOGIC
and ground, thus providing a predictable output under a
wide range of input and output conditions.
CONNECTION DIAGRAMS
8-Pin Plastic Mini-DIP (N)
and Cerdip (Q) Packages
8-Pin SOIC (R) Package
AD790–SPECIFICATIONS
DUAL SUPPLYNOTESDefined as the average of the input voltages at the low to high and high to low transition points. Refer to Figure 14.Defined as half the magnitude between the input voltages at the low to high and high to low transition points. Refer to Figure 14.+VS must be no lower than (VLOGIC –0.5 V) in any supply operating conditions, except during power up.
All min and max specifications are guaranteed. Specifications shown in boldface are tested on all production units at final test.
Specifications subject to change without notice.
(Operation @ +258C and +VS = +15 V, –VS = –15 V, VLOGIC = +5 V unless otherwise noted)
SINGLE SUPPLYINPUT CHARACTERISTICS
LATCH CHARACTERISTICS
SUPPLY CHARACTERISTICS
TEMPERATURE RANGE
NOTESPin 1 tied to Pin 8, and Pin 4 tied to Pin 6.Defined as the average of the input voltages at the low to high and high to low transition points. Refer to Figure 14.Defined as half the magnitude between the input voltages at the low to high and high to low transition points. Refer to Figure 14.–VS must not be connected above ground.
All min and max specifications are guaranteed. Specifications shown in boldface are tested on all production units at final test.
Specifications subject to change without notice.
AD790
(Operation @ +258C and +VS = VLOGIC = +5 V, –VS = 0 V unless otherwise noted)1
AD790
ABSOLUTE MAXIMUM RATINGS1, 2Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .±18 V
Internal Power Dissipation2 . . . . . . . . . . . . . . . . . . .500 mW
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . .±16.5 V
Output Short Circuit Duration . . . . . . . . . . . . . . . .Indefinite
Storage Temperature Range
(N, R) . . . . . . . . . . . . . . . . . . . . . . . . . . .–65°C to +125°C
(Q) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .–65°C to +150°C
Lead Temperature Range (Soldering 60 sec) . . . . . . .+300°C
Logic Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 V
METALIZATION PHOTOGRAPHContact factory for latest dimensions.
Dimensions shown in inches and (mm).
Call factory for chip specifications.
AD790
0.1µF
0.1µF
0.1µF
15V+
+IN
–IN+
OUTPUT
15V–
LATCH
(OPTIONAL)Figure 1.Basic Dual Supply
Configuration (N, Q Package Pinout)
NOTESStresses above those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in
the operational sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.Thermal characteristics: plastic N-8 package: θJA = 90°C/watt; ceramic Q-8
package: θJA = 110°C/watt, θJC = 30°C/watt. SOIC (R-8) package: θJA = 160°C
watt; θJC = 42°C/watt.
ORDERING GUIDE
+IN
–INFigure 2.Basic Single Supply
Configuration (N, Q Package Pinout)
AD790
+5V+15V
–15V
TEK
SCOPE
–5V
VOLTAGE
SOURCE
–5mV
0.1µF
–100mV
–1.3V
–1.7V
–5V
HP8112
PULSE
GENERATOR
HP2835
MPS
0.1µF0.1µF 10kΩ 650Ω 400Ω 50Ω
AD790
CIRCUIT DESCRIPTIONThe AD790 possesses the overall characteristics of a standard
monolithic comparator: differential inputs, high gain and a logic
output. However, its function is implemented with an architec-
ture which offers several advantages over previous comparator
designs. Specifically, the output stage alleviates some of the limi-
tations of classic “TTL” comparators and provides a symmetric
output. A simplified representation of the AD790 circuitry is
shown in Figure 13.
OUTPUT
GAIN STAGEOUTPUT STAGEIN+–
VLOGIC
GNDFigure 13.AD790 Block Diagram
The output stage takes the amplified differential input signal and
converts it to a single-ended logic output. The output swing is
defined by the pull-up PNP and the pull-down NPN. These pro-
duce inherent rail-to-rail output levels, compatible with CMOS
logic, as well as TTL, without the need for clamping to internal
bias levels. Furthermore, the pull-up and pull-down levels are
symmetric about the center of the supply range and are refer-
enced off the VLOGIC supply and ground. The output stage has
nearly symmetric dynamic drive capability, yielding equal rise
and fall times into subsequent logic gates.
Unlike classic TTL or CMOS output stages, the AD790 circuit
does not exhibit large current spikes due to unwanted current
flow between the output transistors. The AD790 output stage
has a controlled switching scheme in which amplifiers A1 and
A2 drive the output transistors in a manner designed to reduce
the current flow between Q1 and Q2. This also helps minimize
the disturbances feeding back to the input which can cause
troublesome oscillations.
The output high and low levels are well controlled values de-
fined by VLOGIC (+5 V), ground and the transistor equivalent
“Schottky” clamps and are compatible with TTL and CMOS
logic requirements. The fanout of the output stage is shown in
Figure 6 for standard LSTTL or HCMOS gates. Output drive
behavior vs. capacitive load is shown in Figure 5.
HYSTERESISThe AD790 uses internal feedback to develop hysteresis about
the input reference voltage. Figure 14 shows how the input off-
set voltage and hysteresis terms are defined. Input offset voltage
= HYSTERESIS VOLTAGEHV
VOUT+
VOS= INPUT OFFSET VOLTAGE2+
OUTV
GNDFigure 14. Hysteresis Definitions (N, Q Package Pinout)
hysteresis range. This built-in hysteresis allows the AD790 to
avoid oscillation when an input signal slowly crosses the ground
level.
SUPPLY VOLTAGE CONNECTIONSThe AD790 may be operated from either single or dual supply
voltages. Internally, the VLOGIC circuitry and the analog front-
end of the AD790 are connected to separate supply pins. If dual
supplies are used, any combination of voltages in which +VS ≥
VLOGIC – 0.5 V and –VS ≤ 0 may be chosen. For single supply
operation (i.e., +VS = VLOGIC), the supply voltage can be oper-
ated between 4.5 V and 7 V. Figure 15 shows some other ex-
amples of typical supply connections possible with the AD790.
BYPASSING AND GROUNDINGAlthough the AD790 is designed to be stable and free from os-
cillations, it is important to properly bypass and ground the
power supplies. Ceramic 0.1 μF capacitors are recommended
and should be connected directly at the AD790’s supply pins.
These capacitors provide transient currents to the device during
comparator switching. The AD790 has three supply voltage
pins, +VS, –VS and VLOGIC. It is important to have a common
ground lead on the board for the supply grounds and the GND
pin of the AD790 to provide the proper return path for the sup-
ply current.
LATCH OPERATIONThe AD790 has a latch function for retaining input information
at the output. The comparator decision is “latched” and the
output state is held when Pin 5 is brought low. As long as Pin 5
is kept low, the output remains in the high or low state, and
does not respond to changing inputs. Proper capture of the in-
put signal requires that the timing relationships shown in Fig-
ure 12 are followed. Pin 5 should be driven with CMOS or
TTL logic levels.
The output of the AD790 will respond to the input when Pin 5
is at a high logic level. When not in use, Pin 5 should be con-
nected to the positive logic supply. When using dual supplies, it
