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参数资料
| 型号： | LT1239CS#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16 |
| 封装： | 0.150 INCH, PLASTIC, SOP-16 |
| 文件页数： | 3/12页 |
| 文件大小： | 235K |
| 代理商： | LT1239CS#TR |
11
LT1239
APPLICATIONS INFORMATION
WU
U
backup batteries have been completely discharged. Once the
backup batteries are charged the power in regulator 1 drops
significantly. The power in regulator 2 when regulator 2 is
providing power to the memory will be equal to:
(VBACKUPBATTERY – 4.85V) × IOUT
IOUT is the current needed to power the memory and power
monitoring circuitry.
Example: (6.8V – 4.85V)
× 30mA = 58.5mW
The power in the comparator when the comparator is provid-
ing power to the memory will be equal to:
(VSAT × IOUT)
IOUT is the current needed to power the memory and power
monitoring circuitry. Comparator Output Saturation Voltage
vs Output Current can be found in the Typical Performance
Characteristics.
Example: (VSAT × ILOAD) = (0.15V × 30mA) = 4.5mW
Note that power for memory will be supplied by either
regulator 2 or the comparator. The power in the error
amplifier when the cells are unequalized will be equal to:
(VBACKUPBATTERY/2) × 3mA
Example: (6.8V/2)
× 3mA = 10.2mW
This component goes to zero when the cell voltages are
equalized.
The thermal resistance of the LT1239 is 120
°C/W when
the device is mounted to a PC board with at least one
ground or power plane. The junction temperature rise will
be equal to the total power in the device multiplied by
120
°C/W or (PTOTAL × 120°C/W). For 300mW dissipation
the junction temperature rise will be (300mW
× 120°C/W)
= 36
°C. Given that the thermal limit temperature is ap-
proximately 100
°C, this allows for a maximum ambient
temperature of roughly 60
°C before the device thermal
limits. This temperature is near the maximum ambient
allowed for most battery types.
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Figure 5. Adding a Protection Resistor for Lithium-Ion Charger
LT1239
IN 1
GND
OUT 1
IMON1
ADJ
E/A (IN)
E/A (0UT)
R3
604k
LT1239 F05
+
10
F
MAIN
BATTERY
PACK
R4 >
V1 – V2
MAX CHARGE CURRENT
R2
69.8k
R1
681k
V1
V2
3.4V Li-Ion
CELL
3.4V Li-Ion
CELL
*R4
C1
300pF
*THIS RESISTOR IS REQUIRED
BY SOME SAFETY AGENCIES.
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