app3064| Application Note
Application Note 3064 Powering Up a DS2761
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Introduction
The DS2761 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 DS2761
When the DS2761 goes through its power on reset (POR) sequence, the device begins in Sleep Mode until a condition that brings the device into Active Mode is encountered. In the following powering up cases of the DS2761, all device EEPROM is recalled to the shadow RAM during the POR sequence. At power up, the Accumulated Current Register (ACR) is reset to 0.00mAhrs and the User RAM is undefined. The following table contains the conditions at power up that will be examined in this Application Note. CASE A B C D -0 1 1 POWER UP CONDITIONS PMOD SWEN ----DQ 0 1 1 1 VIN --> VUV < VUV
Case A: DQ = 0
If DQ is low when power is first applied to a DS2761, the device stays in Sleep Mode. 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 remains disabled. When DQ is low, the state of PMOD has no effect on the control pins because the device will not wake up in either case. The waveform in this case is also independent of the cell's voltage in relation to the under voltage threshold (VUV).
Figure 1. DQ = 0
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