14

LPV821

SNOSD36 – AUGUST 2017

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Copyright © 2017, Texas Instruments Incorporated

Typical Applications (continued)

In case a bi-direction current sensing is required, for symmetric load current of –1 A to 1 A, the voltage divider

resistors R5 and R6 must be equal. To minimize power consumption, 100-kΩ resistors with a tolerance of 0.5%

were selected.

To set the gain of the difference amplifier, the common-mode range and output swing of the LPV821 must be

considered. The gain of the difference amplifier can now be calculated as shown below

(7)

10 Power Supply Recommendations

The LPV821 is specified for operation from 1.7 V to 3.6 (±0.85 V to ±1.8 V); many specifications apply from

–40°C to 125°C. The Typical Characteristics presents parameters that can exhibit significant variance with regard

to operating voltage or temperature.

CAUTION

Supply voltages larger than 4 V can permanently damage the device (see the Absolute

Maximum Ratings).

TI recommends placing 0.1-μF bypass capacitors close to the power-supply pins to reduce errors coupling in

from noisy or high-impedance power supplies. For more detailed information on bypass capacitor placement,

refer to the Layout section.

11 Layout

11.1 Layout Guidelines

11.1.1 General Layout Guidelines

Pay attention to good layout practices. Keep traces short and when possible, use a printed-circuit-board (PCB)

ground plane with surface-mount components placed as close to the device pins as possible. Place a 0.1-μF

capacitor closely across the supply pins. Apply these guidelines throughout the analog circuit to improve

performance and provide benefits, such as reducing the electromagnetic interference (EMI) susceptibility.

Operational amplifiers vary in susceptibility to radio frequency interference (RFI). RFI can generally be identified

as a variation in offset voltage or DC signal levels with changes in the interfering RF signal. The LPV821 is

specifically designed to minimize susceptibility to RFI and demonstrates remarkably low sensitivity compared to

previous generation devices. Strong RF fields may still cause varying offset levels.

11.2 Layout Example

Figure 26. SOT-23 Layout Example