ꢀ ꢁ ꢂ ꢃꢄ ꢅ ꢂꢆ ꢀ ꢁ ꢂ ꢃꢄꢅ ꢇ
SLUS553D − MAY 2003 − REVISED JULY 2005
DESCRIPTION (continued)
The battery voltage limit can be programmed by using the internal 1.196-V, 0.5% precision reference, making it
suitable for the critical charging demands of lithium-ion cells. Also, the bq24702/bq24703 provides an option to
override the precision reference and drive the error amplifier either directly from an external reference or from a
resistor divider off the 5 V supplied by the integrated circuit.
The selector function allows the manual selection of the system power source, battery or wall-adapter power. The
bq24702/bq24703 supports battery-conditioning and battery-learn cycles through the ACSEL function. The ACSEL
function allows manual selection of the battery or wall power as the main system power. It also provides autonomous
switching to the remaining source (battery or ac power) should the selected system power source terminate (refer
to Table 1 for the differences between the bq24702 and the bq24703). The bq24702/bq24703 also provides an alarm
function to indicate a depleted battery condition.
The bq24702/bq24703 PWM controller is ideally suited for operation in a buck converter for applications when the
wall-adapter voltage is greater than the battery voltage.
DISSIPATION RATINGS
MAXIMUM POWER DISSIPATION
(LOW K BOARD)
MAXIMUM POWER DISSIPATION
(HIGH K BOARD)
vs
vs
FREE-AIR TEMPERATURE
FREE-AIR TEMPERATURE
1.40
1.20
1
1.60
1.40
1.20
1
MAX Pd (W) @ 500 LFM
MAX Pd (W) @ 250 LFM
MAX Pd (W) @ 500 LFM
MAX Pd (W) @ 250 LFM
MAX Pd (W) @ 150 LFM
MAX Pd (W) @ 0 LFM
MAX Pd (W) @ 150 LFM
MAX Pd (W) @ 0 LFM
0.80
0.60
0.40
0.80
0.60
0.40
0.20
0
θ
θ
θ
θ
= 89.37 C/W @ 0 LFM,
= 77.98 C/W @ 150 LFM,
= 73.93 C/W @ 250 LFM,
= 68.23 C/W @ 500 LFM
JA
JA
JA
JA
θ
θ
θ
θ
= 150.17 C/W @ 0 LFM,
= 110.95 C/W @ 150 LFM,
= 99.81 C/W @ 250 LFM,
= 86.03 C/W @ 500 LFM
JA
JA
JA
JA
0.20
0
25
50
70
85
25
50
70
85
T
A
− Free-Air Temperature − °C
T
A
− Free-Air Temperature − °C
†
‡
The JEDEC low K (1s) board design used to derive this data was a 3-inch x 3-inch, two layer board with 2 ounce copper traces on top of the board.
The JEDEC high K (1s) board design used to derive this data was a 3-inch x 3-inch, multilayer board with 1 ounce internal power and ground
planes and 2 ounce copper traces on top and bottom of the board.
2
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