CMC7101A Datasheet, PDF (8/10 Pages) California Micro Devices Corp – CMC7101A Low Power Operational Amplifier, RRIO, SOT23-5

CALIFORNIA MICRO DEVICES
CMC7101A
Application Benefits
1.0 Packaging
Most of the benefits of the CMC7101A are due to the use of
a SOT package. The industry has readily adopted the SMT
package technique and a SOT23-5 footprint is an easy way
to save space. This leads to smaller finished products.
PC CARDS (PCMCIA type III cards) require low profile
components. At 0.056 inches (1.43 mm), the CMC7101A
is ideal.
1.1 Signal Integrity
As products become smaller, the natural space used to
isolate circuits is lost. Signals can interact or pick up
noise in these designs. By using a physically smaller
amplifier package, the CMC7101A can be placed closer
to the signal source, reducing noise pickup, and its small
size makes it a simple buffer.
Rail to Rail Inputs and Output allow the amplifier to
operate from lower supplies and also maintain signal
level swings under large signal amplitude conditions.
1.2 Simplified Board Layout
Board layout is helped in a couple of ways due to the
small size. Op Amps can be placed where amps are
needed, shortening signal paths and PCB traces subject
to noise pick up. Compared to a dual or quad device,
two or four strategically placed SOT AMPs reduce cross-
talk and avoid long PC wiring traces.
1.3 Lower Distortion
The CMC7101A has lower distortion than other SOT
Amps, which combined with the high open loop gain
allows it to achieve very low audio signal distortion.
1.4 Lower Power Supply Current Drain
The CMC7101A has lower power supply drain than other
SOT Amps, making the part an instant upgrade to
industry standard ‘7101’ applications. Lower supply
current means longer operation in battery operated
products, and simpler power supply regulator or
converter designs when many amplifiers are used in one
system.
1.5 Higher Output Drive
The CMC7101A has higher output current than other
SOT Amps, making the part an instant upgrade to industry
standard ‘7101’ applications. Higher output current
means that existing circuits can start up sooner when
power is applied (due to output current charging load
capacitance), a feature needed when sections of a system
are powered down frequently to save power or reduce
cross-talk, such as a cellular handset.
Application Trouble Shooting
2.0 Input Common Mode Range and Output
Voltage Considerations
The CMC7101A is capable of accommodating input
common mode and output voltages equal to both
power supply rails. Nor will voltages that exceed the
supply voltages cause phase inversion of the output.
However, ESD diode clamps are provided at the inputs
that can be damaged if static currents in excess of ± 5
mA are allowed to flow through them. This can occur
when the magnitude of input voltage exceeds the rail
by more than 0.3 volt. To preclude damage, an current
limiting resistor, R_s, in series with the input is
recommended as illustrated in Figure 1 whose value
for R_s is given by:
Vin - (V+ + 0.3 V)
R_s > ————————————
(1)
5 mA
For V+ (or V-) equal to 2.7 volts and Vin equal to
10 volts, Rs should be chosen for a value of 1.5 KΩ
or greater.
Figure 1 R_S Input Current Protection
2.1 Output Current and Power Dissipation
Considerations
The CMC7101A is capable of sinking and sourcing
output currents in excess of 75 mA at voltages very
nearly equal to the rails. As such, it does not have any
internal short circuit protection (which would in any
event detract from its rail to rail capability). Accordingly,
power dissipation and junction temperature should be
considered in any application.
Obviously, the worst case from a power dissipation
point of view is when the output is shorted to either
ground in a single rail application or to the opposite
supply voltage in split rail applications. Since this device
only draws 300 micro Amps supply current, its
contribution to the junction temperature, T_J, is
negligible. As an example, let us analyze a situation in
©2000 California Micro Devices Corp. All rights reserved.
8
215 Topaz Street, Milpitas, California 95035 Tel: [phone] Fax: [phone] www.calmicro.com
2/00