ISL78693 Datasheet, PDF (9/18 Pages) Intersil Corporation – Reverse battery leakage 700nA

ISL78693
Typical Operating Performance The test conditions for the typical operating performance are: V_IN = 5V,
T_A = +25°C, R_IREF = 160kΩ, V_BAT = 3.7V, unless otherwise noted. (Continued)
0.6
0.5
0.4
0.3
+70°C
0.2
+75°C
0.1
+85°C
0.0
2.2
2.7
3.2
3.7
4.2
V_BAT (V)
FIGURE 17. V_BAT vs I_BAT vs AMBIENT TEMPERATURE,
R_IREF = 200k, V_IN = 5.5V, AIR FLOW = 0 LFM,
MEASURED ON THE ISL78693EVAL1Z BOARD
110
105
100
95
90
85
80
+70°C
75
70
+75°C
65
+85°C
60
2.2
2.7
3.2
3.7
4.2
V_BAT (V)
FIGURE 18. JUNCTION TEMPERATURE vs V_BAT vs AMBIENT
TEMPERATURE, R_IREF = 200k, V_IN = 5.5V,
AIR FLOW = 0 LFM, MEASURED ON THE
ISL78693EVAL1Z BOARD
Theory of Operation
The ISL78693 is an integrated charger for single-cell Lithium
chemistry batteries. The ISL78693 functions as a traditional
linear charger when powered with a voltage source adapter.
When powered with a current-limited adapter, the charger
minimizes the thermal dissipation commonly seen in traditional
linear chargers.
As a linear charger, the ISL78693 charges a battery in the
popular Constant Current (CC) and Constant Voltage (CV) profile.
The constant charge current I_REF is programmable up to 1A with
an external resistor or a logic input. The charge voltage VCH has
1% accuracy over the entire recommended operating condition
range. The charger preconditions the battery with a 10% typical
of the programmed current at the beginning of a charge cycle
until the battery voltage is verified to be above the minimum fast
charge voltage, V_TRICKLE. This low current preconditioning
charge mode is named Trickle mode. The verification takes 15
cycles of an internal oscillator whose period is programmable
with a timing capacitor on the time pin. A thermal-foldback
feature protects the device from the thermal concern typically
seen in linear chargers. The charger reduces the charge current
automatically as the IC internal temperature rises above +100°C
to prevent further temperature rise. The thermal-foldback feature
ensures safe operation when the Printed Circuit Board (PCB) is
space limited for thermal dissipation.
A TEMP pin monitors the battery temperature to ensure a safe
charging temperature range. The temperature range is
programmable with an external negative temperature coefficient
(NTC) thermistor. The TEMP pin is also used to detect the removal
of the battery.
The charger offers a safety timer for setting the fast charge time
(TIMEOUT) limit to prevent charging a dead battery for an
extensively long time. The Trickle mode is limited to 1/8 of
TIMEOUT.
The charger automatically recharges the battery when the
battery voltage drops below a recharge threshold of 3.3V
(typical). When the input supply is not present, the ISL78693
draws less than 1µA current from the battery.
Three indication pins are available from the charger to indicate
the charge status. The V2P8 outputs a 2.8VDC voltage when the
input voltage is above the Power-On Reset (POR) level and can be
used as the power-present indication. This pin is capable of
sourcing a 2mA current, so it can also be used to bias external
circuits. The STATUS pin is an open-drain, logic output that turns
LOW at the beginning of a charge cycle until the End-of-charge
(EOC) condition is qualified. The EOC condition is when the
battery voltage rises above the recharge threshold and the
charge current falls below a preset of a tenth of the programmed
charge current. Once the EOC condition is qualified, the STATUS
output rises to HIGH and is latched. The latch is released at the
beginning of a charge or recharge cycle. The open-drain FAULT
pin turns low when any fault conditions occur. The fault
conditions include the external battery temperature fault, a
charge time fault, or the battery removal.
Figure 19 on page 10 shows the typical charge curves in a
traditional linear charger powered with a constant voltage
adapter. From top to bottom, the curves represent the constant
input voltage, the battery voltage, the charge current, and the
power dissipation in the charger. The power dissipation P_CH is
given by Equation 1:
P_CH = V_IN-V_BAT  I_CHARGE
(EQ. 1)
where I_CHARGE is the charge current. The maximum power
dissipation occurs during the beginning of the CC mode. The
maximum power the IC is capable of dissipating is dependent on
the thermal impedance of the Printed Circuit Board (PCB).
Figure 19 shows (with dotted lines) two cases that the charge
currents are limited by the maximum power dissipation
capability due to the thermal foldback.
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FN8891.1
December 12, 2016