Amplifier and Data Converter Selection Guide

22 Amplifiers
➔
Comparators
Comparator ICs are specialized op amps
designed to compare two input voltages and
provide a logic state output. They can be
considered one-bit analog-to-digital
converters.
The TI comparator portfolio consists of a
variety of products with various performance
characteristics, including: fast (ns) response
time, wide input voltage ranges, extremely
low quiescent current consumption and op
amp and comparator combination ICs.
Comparator vs. Op Amp
Comparator Op Amp
Speed (Response time) Yes No
Logic Output Yes No
Wide Diff. Input Range Yes Yes
Low Offset Drift No Yes
In general, if a fast response time is required,
use a comparator.
Design Considerations
Output topology
• Open collector—connects to the logic
supply through a pull-up resistor and
allows comparators to interface to a
variety of logic families.
• Push-pull—does not require a pull-up
resistor. Because the output swings rail-torail,
the logic level is dependent on the
voltage supplies of the comparator.
Response time (propagation delay)—
applications requiring “near real-time”
signal response should consider comparators
with nanosecond (ns) propagation delay. Note
that as propagation delay decreases, supply
current increases. Evaluate what mix of
performance and power can be afforded. The
TLV349x family offers a unique combination
of speed/power with 5µs propagation delay
on only 1µA of quiescent current.
Combination comparator and op amp—for
input signals requiring DC level shifting and/or
Slower Faster
Response Time Low-to-High (µs)
Increasing Speed
0.006
0.0078
0.025
0.115
0.2
0.3
1
1.1
7
36
80
Push-Pull Output
Open-Drain Output
1.4
1.8
LMV331, LMV393, LMV339
TLV3491, TLV3492
gain prior to the comparator, consider the
TLV230x (open drain) or TLV270x (push-pull) op
amp and comparator combinations. These dual
function devices save space and cost.
Comparator and voltage reference—
comparators typically require a reference
voltage to compare against. The TLV3011 is
an integrated comparator and voltage
reference combination in a space-saving
SC70 package.
TLV3501 S, 12mA/ch
TL714 S, 12mA/ch
TL3016 S, 12.5mA/ch
TL712
TLC352, TLC354
TLC372, TLC374
LM393, LM339
TLC393, TLC339
TLC3702, TLC3704
S, 20mA/ch
LM211
TLV3701, TLV3702, TLV3704
TLV3401, TLV3402, TLV3404
S, D, Q, 100µA/ch
S, D, Q, 1.2µA/ch
D, Q, 150µA/ch
D, Q, 150µA/ch
D, Q, 20µA/ch
D, Q, 20µA/ch
S, D, Q, 0.8µA/ch
S, D, Q, 0.55µA/ch
3.3 5 16 30
Supply Voltage (V)
S, 6mA/ch
D, Q, 500µA/ch
High-Speed Comparator in SOT23
TLV3501
Get samples and datasheets at: www.ti.com/sc/device/TLV3501
Key Features
• High speed: 4.5ns response at 20mV
overdrive
• Beyond-the-rail common-mode input range
• Rail-to-rail, push-pull output
• Single-supply operation: 2.7V to 5.5V
• Packaging: SOT23
Applications
• Test and measurement
• Power supply monitoring
• Base stations
The TLV3501 is a high-speed comparator in a small SOT23 package. Designed for a variety of
applications, TLV3501 offers very fast response relative to power consumption. It is specified
over the extended temperature range of –40°C to +125°C.
Propagation Delay (ns)
9
8
7
6
5
4
PROPAGATION DELAY vs. OVERDRIVE VOLTAGE
Fall
Rise
V CM = 1V
V S = 5V
C LOAD = 17pF
3
0 20 40 60 80 100
Overdrive Voltage (mV)
TLV3501 performance
characteristics.
Amplifier and Data Converter Selection Guide Texas Instruments 3Q 2006