app3065| Application Note
Application Note 3065 Powering up a DS2762
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Introduction
The DS2762 High-Precision Battery Monitor provides monitoring and protection for a Li+ cell. When the device powers up, the state of the DQ pin, the Power Mode bit (PMOD) and the battery voltage can affect what mode the device enters and how the Charge Control (CC) and Discharge Control (DC) pins react. This Application Note will provide details of what happens in many possible powering up scenarios.
Powering Up a DS2762
When a DS2762 goes through its power on reset (POR) sequence, it begins in Active Mode and then makes a decision based on the cell voltage, the state of the DQ pin, and the PMOD bit to determine if it needs to go into Sleep Mode. The SWEN bit does not effect the actions of the DS2762 when it powers on. In the following powering up cases of the DS2762, all device EEPROM is recalled to the shadow RAM during the POR sequence. Also, the state of the Accumulated Current Register (ACR) and the User RAM are undefined at power up. The following table contains the conditions at power up that will be examined in this Application Note. CASE A B C D E 1 -0 --POWER UP CONDITIONS PMOD SWEN -----DQ 0 0 0 1 1 VIN > VUV < VUV > VUV > VUV < VUV
Case A: DQ = 0, PMOD = 1, Cell > VUV
If DQ is low and PMOD is 1, the DS2762 powers up in Active Mode with the CC and DC pins driven low to enable the PAC+ output. The device then enters Sleep Mode when it has detected that DQ has been low for 2 seconds. At that time, the DC pin is pulled to the cell voltage, which disables the PAC+ terminal. The PAC+ terminal is pulled low when the device is in Sleep Mode. The CC pin is pulled to PAC+, so that CC is low, but the charge FET is now disabled.
Figure 1. DQ = 0, PMOD = 1, Cell > VUV
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