SNVSB04B March 2019 – June 2020 TLV4021 , TLV4031 , TLV4041 , TLV4051

UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.

- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
- 8 Application and Implementation
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information

Configure the circuit as shown in Figure 44. Connect (V+) to 3.3 V which also powers the micro-controller. Resistors R_{1} and R_{2} create the under-voltage alert level of 2.0 V. When the battery voltage sags down to 2.0 V, the resistor divider voltage crosses the (V_{IT-}) threshold of the TLV4041R1. This causes the comparator output to transition from a logic high to a logic low. The push-pull option of the TLV40x1 family is selected since the comparator operating voltage is shared with the microcontroller which is receiving the under-voltage alert signal. The TLV4041 option with the 1.2 V internal reference is selected because it is the closest internal reference option that is less than the critical under-voltage level of 2.0 V. Choosing the internal reference option that is closest to the critical under-voltage level minimizes the resistor divider ratio which optimizes the accuracy of the circuit. Error at the falling edge threshold of (V_{IT-}) is amplified by the inverse of the resistor divider ratio. So minimizing the resistor divider ratio is a way of optimizing voltage monitoring accuracy.

Equation 1 is derived from the analysis of Figure 44.

Equation 1.

where

- R
_{1}and R_{2}are the resistor values for the resistor divider connected to IN - V
_{BAT}is the voltage source that is being monitored for an undervoltage condition. - V
_{IT-}is the falling edge threshold where the comparator output changes state from high to low

Rearranging Equation 1 and solving for R_{1} yields Equation 2.

Equation 2.

For the specific undervoltage detection of 2.0 V using the TLV4041R1, the following results are calculated.

Equation 3.

where

- R
_{2}is set to 1 MΩ - V
_{BAT}is set to 2.0 V - V
_{IT-}is set to1.18 V

Choose R_{TOTAL} (R_{1} + R_{2}) such that the current through the divider is at least 100 times higher than the input bias current (I_{BIAS}). The resistors can have high values to minimize current consumption in the circuit without adding significant error to the resistive divider.