參數(shù)資料
型號(hào)： LP3972SQXE514
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 電源管理
英文描述： 1-CHANNEL POWER SUPPLY SUPPORT CKT, QCC40
封裝： 5 X 5 MM, LLP-40
文件頁數(shù)： 7/60頁
文件大?。?/td> 1171K
代理商： LP3972SQXE514
Back-Up Charger Electrical Characteristics
Unless otherwise noted, V
IN = VBATT = 3.6V. Typical values and limits appearing in normal type apply for TJ = 25°C. Limits appearing
in boldface type apply over the entire junction temperature range for operation, 40°C to +125°C. (Note 2, Note 6) and (Note 8).
Symbol
Parameter
Conditions
Min
Typ
Max
Units
V
IN
Operational Voltage Range
Voltage at V
IN
3.3
5.5
V
I
OUT
Backup Battery Charging Current
V
IN = 3.6V, Backup_Bat = 2.5V,
Backup Battery Charger Enabled
190
μA
V
OUT
Charger Termination Voltage
V
IN = 5.0V Backup Battery Charger
Enabled. Programmable
2.91
3.1
V
Backup Battery Charger Short Circuit
Current
Backup_Bat = 0V, Backup Battery
Charger Enabled
9
mA
PSRR
Power Supply Ripple Rejection Ratio I
OUT ≤ 50 μA, VOUT = 3.15V
V
OUT + 0.4 ≤ VBATT = VIN ≤ 5.0V
f < 10 kHz
15
dB
I
Q
Quiescent Current
I
OUT < 50 μA
25
μA
C
OUT
Output Capacitance
0 μA
≤ I
OUT ≤ 100 μA
0.1
μF
Output Capacitor ESR
5
500
m
LP3972 Battery Switch Operation
The LP3972 has provisions for two battery connections, the
main battery V
BAT and Backup Battery
The function of the battery switch is to connect power to the
LDO_RTC from the appropriate battery, depending on con-
ditions described below:
If only the backup battery is applied, the switch will auto-
matically connect the LDO_RTC power to this battery.
If only the main battery is applied, the switch will auto-
matically connect the LDO_RTC power to this battery
If both batteries are applied, and the main battery is suf-
ficiently charged (V
BAT > 3.1V), the switch will automatically
connect the LDO_RTC power to the main battery.
As the main battery is discharged a separate circuit called
nBATT_FLT will warn the system. Then if no action is taken
to restore the charge on the main battery, and discharging is
continued the battery switch will disconnect the input of the
LDO_RTC from the main battery and connect to the backup
battery.
The main battery voltage at which the LDO_RTC is
switched over from main to backup battery is 2.8V typically.
There is a hysteric voltage in this switch operation, thus
the LDO_RTC will not be reconnected to main battery until
main battery voltage is greater than 3.1V typically.
The system designer may wish to disable the battery
switch when only a main battery is used. This is accomplished
by setting the “no back up battery bit” in the control register
8h’0B bit 7 NBUB. With this bit set to “1”, the above described
switching will not occur, that is the LDO_RTC will remain con-
nected to the main battery even as it is discharged below the
2.9V threshold. The Backup battery input should also be con-
nected to main battery.
15
www.national.com
LP3972
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LP3972SQX-E514 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
LP3972SQX-E514/NOPB 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
LP3972SQX-I414/NOPB 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
LP3972SQX-I514 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
LP3972SQX-I514/NOPB 功能描述:PMIC 解決方案 RoHS:否 制造商:Texas Instruments 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel
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