LPV521_15 Datasheet, PDF (25/33 Pages) Texas Instruments – LPV521 NanoPower, 1.8-V, RRIO, CMOS Input, Operational Amplifier

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LPV521
SNOSB14D – AUGUST 2009 – REVISED DECEMBER 2014
Typical Applications (continued)
Selecting values per Figure 68 will limit the current traveling through the R₁ – Q1 – R₃ leg of the circuit to under 1
µA which is on the same order as the LPV521 supply current. Increasing resistors R₁ , R₂ , and R₃ will decrease
the measuring circuit supply current and extend battery life.
Decreasing R_SENSE will minimize error due to resistor tolerance, however, this will also decrease V_SENSE =
I_CHARGE × R_SENSE, and in turn the amplifier offset voltage will have a more significant contribution to the total error
of the circuit. With the components shown in Figure 68 the measurement circuit supply current can be kept below
1.5 µA and measure 100 µA to 1 mA.
8.2.3.3 Application Curve
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
0.25
0.5
0.75
1
ICHARGE (mA)
1.25
1.5
C001
Figure 69. Calculated High-Side Current Sense Circuit Output
9 Power Supply Recommendations
The LPV521 is specified for operation from 1.6 V to 5.5 V (±0.8 V to ±2.75 V) over a –40°C to 125°C
temperature range. Parameters that can exhibit significant variance with regard to operating voltage or
temperature are presented in the Typical Characteristics.
CAUTION
Supply voltages larger than 6 V can permanently damage the device.
Low bandwidth nanopower devices do not have good high frequency (>1KHz) AC PSRR rejection against high-
frequency switching supplies and other kHz and above noise sources, so extra supply filtering is recommended if
kHz range noise is expected on the power supply lines.
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