DS2784G+ Maxim Integrated Products, DS2784G+ Datasheet - Page 11

• Manufacturer Part Number: DS2784G+
• Description: IC FUEL GAUGE STND-ALONE 14-TDFN
• Manufacturer: Maxim Integrated Products

Specifications of DS2784G+

• Function: Fuel, Gas Gauge/Monitor
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 2.5 V ~ 4.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 14-TDFN
• Product: Fuel Gauges
• Operating Supply Voltage: 2.5 V to 4.6 V
• Supply Current: 85 uA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Charge Safety Timers: Yes
• Mounting Style: SMD/SMT
• Temperature Monitoring: Yes
• Uvlo Start Threshold: 2.4 V
• Uvlo Stop Threshold: 2.5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DS2784: 1-Cell Stand-Alone Fuel Gauge IC with Li+ Protector and SHA-1 Authentication
POWER MODES
The DS2784 has two power modes: Active and Sleep. On initial power-up, the DS2784 defaults to Active mode. In
Active mode, the DS2784 is fully functional with measurements and capacity estimation registers continuously
updated. The protector circuit monitors the battery voltages and current for unsafe conditions. The protection FET
gate drivers are enabled when conditions are deemed safe. Also, the SHA-1 authentication function is available in
Active mode. When a SHA-1 computation is performed, the supply current increases to I
for t
. In Sleep mode,
DD3
SHA
the DS2784 conserves power by disabling measurement and capacity estimation functions, but preserves register
contents. Gate drive to the protection FETs is disabled in Sleep. And the SHA-1 authentication feature is not
operational.
Sleep mode is entered under two different conditions: bus low and undervoltage. An enable bit makes entry into
Sleep optional for each condition. Sleep mode is not entered if a charger is connected (V
> V
+ 50mV) or if a
PLS
DD
charge current of 1.6mV / R
is measured from SNS to V
. The DS2784 exits Sleep mode upon charger
SNS
SS
connection and V
≥ V
or a low to high transition on DQ.
IN
UV
The bus-low condition, where the DQ pin is low for t
, indicates pack removal or system shutdown in which the
SLEEP
1-Wire bus pullup voltage, V
, is not present. The Power mode (PMOD) bit must be set to enter Sleep when a
PULLUP
bus-low condition occurs. After the DS2784 enters Sleep due to a bus-low condition, it is assumed that no charge
or discharge current will flow and that coulomb counting is unnecessary.
The second condition to enter Sleep is an undervoltage condition, which reduces battery drain due to the DS2784
supply current and prevents over discharging the cell. The DS2784 transitions to Sleep if the V
voltage is less
IN
than V
(2.45V typical) and the undervoltage enable (UVEN) bit is set. The 1-Wire bus must be in a static state,
UV
that is, with DQ either high or low for t
. The DS2784 transitions from UVEN Sleep to Active mode when DQ
SLEEP
changes logic state.
The DS2784 has the “power switch” capability for waking the device and enabling the protection FETs when the
host system is powered down. A simple dry-contact switch on the PIO pin or DQ pin can be used to wake up the
battery pack. The power switch function is enabled using the PSPIO and PSDQ configuration bits in the control
register. When PSPIO or PSDQ is set and a Sleep condition is satisfied, the PIO and DQ pins pull high weakly,
then become armed to detect a low-going transition. A 100ms debounce period filters out glitches that can be
caused when a sleeping battery is inserted into a system.
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