SLUS892D December   2009  – December 2019

PRODUCTION DATA.

1. Features
2. Applications
3. Description
1.     Device Images
4. Revision History
5. Description (continued)
6. Device Comparison Table
7. Pin Configuration and Functions
8. Specifications
9. Detailed Description
1. 9.1 Overview
2. 9.2 Functional Block Diagram
3. 9.3 Feature Description
4. 9.4 Device Functional Modes
10. 10Application and Implementation
1. 10.1 Application Information
2. 10.2 Typical Applications
1. 10.2.1 System with Power Path
2. 10.2.2 Simplified System without Power Path or DPM
11. 11Power Supply Recommendations
12. 12Layout
13. 13Device and Documentation Support
14. 14Mechanical, Packaging, and Orderable Information

• RGE|24
• RGE|24

#### 9.3.23 Battery Detection

For applications with removable battery packs, BQ2461x provides a battery-absent detection scheme to reliably detect insertion or removal of battery packs.

Once the device has powered up, an 8-mA discharge current is applied to the SRN terminal. If the battery voltage falls below the LOWV threshold within 1 second, the discharge source is turned off, and the charger is turned on at low charge current (125 mA). If the battery voltage rises above the recharge threshold within 500 ms, there is no battery present and the cycle restarts. If either the 500-ms or 1-second timer times out before its respective threshold is hit, a battery is detected and a charge cycle is initiated.

Ensure that the total output capacitance at the battery node is not so large that the discharge current source cannot pull the voltage below the LOWV threshold during the 1-second discharge time. The maximum output capacitance can be calculated as follows:

Equation 10.

where

• CMAX is the maximum output capacitance.
• IDISCH is the discharge current.
• tDISCH is the discharge time.
• R2 and R1 are the voltage feedback resistors from the battery to the VFB pin.

The 0.5 factor is the difference between the RECHARGE and the LOWV thresholds at the VFB pin.

Example

For a 3-cell Li+ charger, with R2 = 500 kΩ, R1 = 100 kΩ (giving 12.6 V for voltage regulation), IDISCH = 8 mA, tDISCH = 1 second,

Equation 11.

Based on these calculations, no more than 2.7 mF should be allowed on the battery node for proper operation of the battery detection circuit.