ISL78692 Datasheet, PDF (16/18 Pages) Intersil Corporation – Li-ion/Li-Polymer Battery Charger

ISL78692
VIN
VPACK
VIN
VPACK
VIN
VPACK
POWER
CHARGE
CURRENT
TIME
CONSTANT CURRENT CONSTANT VOLTAGE
POWER
CONSTANT RES
CURRENT LIMIT
CHARGE
CURRENT
CONSTANT
VOLTAGE
TIME
POWER
CONSTANT
CURRENT
CHARGE
CURRENT
CONSTANT
VOLTAGE
FIGURE 29A.
FIGURE 29B.
FIGURE 29C.
FIGURE 29. THE OPERATING CURVES WITH THREE DIFFERENT CURRENT LIMITED POWER SUPPLIES
TIME
IREF Programming Using Current-Limited
Adapter
The ISL78692 has 20% tolerance for the charge current.
Typically, the current-limited adapter also has 10% tolerance. In
order to guarantee proper operation, it is recommended that the
nominal charge current be programmed at least 30% higher
than the nominal current limit of the adapter.
Board Layout Recommendations
The ISL78692 internal thermal foldback function limits the
charge current when the internal temperature reaches
approximately +100°C. In order to maximize the current
capability, it is very important that the exposed pad under the
package is properly soldered to the board and is connected to
other layers through thermal vias. More thermal vias and more
copper attached to the exposed pad usually result in better
thermal performance. On the other hand, the number of vias is
limited by the size of the pad. The 3x3 DFN package allows 9 vias
be placed in three rows. Since the pins on the 3x3 DFN package
are on only two sides, as much top layer copper as possible
should be connected to the exposed pad to minimize the thermal
impedance. Refer to UG001, “ISL78692EVAL1Z Evaluation Board
User Guide”for layout example.
V_IN
V_BAT
I_BAT
1 hour
FIGURE 31. SCOPE WAVEFORMS SHOWING THE CASE THAT THE
FULL-LOAD POWER SUPPLY VOLTAGE IS HIGHER THAN
THE CRITICAL VOLTAGE
V_IN
V_BAT
I_BAT
CV Mode
CC Mode
Resistance Limit Mode
FIGURE 30. SCOPE WAVEFORMS SHOWING THE THREE MODE
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FN8692.0
September 10, 2014