The circuit in Figure 2 was designed to create a 0V-1.2V output voltage for a 0A-1A load current, i LOAD. Figure 2 shows an example low-side current-sensing circuit using the TLV379. Measuring the voltage drop across a low-side current-shunt resistor is often the simplest method to determine battery/load current. Table 2 : Error calculations for the TLV379 voltage-measurement circuit shown in Figure 1 The resistor divider tolerance, R TOL, is set to 0.1%.
Table 2 uses the typical specifications for the TLV379 listed in Table 1 to calculate expected circuit performance. Other error sources come from the op-amp’s CMRR and the input bias current flowing through the voltage-divider resistors. The main error contributors in the circuit shown in Figure 1 are the tolerance of the resistors in the divider and the offset voltage of the op amp. However, like most low-power op amps, the TLV379 does not perform well while driving capacitive loads, so check the stability of the circuit when designing output filters with capacitances to GND.įigure 1: Battery-voltage measurement circuit using the TLV379 You can place a low-pass filter at the output of the circuit to limit the signal bandwidth and output noise. Be sure to use high-value resistors for the divider to minimize current consumption. In this case, a 1.8V-5.5V battery voltage will create a 0.393V-1.2V output voltage, which fits within the common 0V-1.2V range for analog-to-digital converters (ADCs) on many low-power microcontrollers.Įquation 1 shows the transfer function for the circuit in Figure 1. To prevent violations of the amplifier’s common-mode input voltage range or output voltage swing, the battery is divided down using R1 and R2. In figure 1, you will see an example battery-voltage measurement circuit using the TLV379 configured as a unity-gain buffer. Table 1 : Key specifications for TLV369 and TLV379 op amps Table 1 lists the key specifications for two new op amps, the TLVx369 and TLVx379 families, which are designed for low-power, cost-sensitive applications. Op amps used in battery-monitoring circuitry must meet the required accuracy levels while consuming minimal power-supply quiescent current, i Q, to conserve battery life. In this post, I’ll demonstrate battery-voltage and current-monitoring circuitry for cost-optimized systems using operational amplifiers (op amps).
#BATTERY MONITOR IC PORTABLE#
In portable electronics designs, typical battery-monitoring systems measure battery voltage and battery current to detect when the battery needs charging or replacement. Other Parts Discussed in Post: TLV369, TLV379
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