參數(shù)資料
型號(hào)： LTC1235CN
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 電源管理
英文描述： Microprocessor Supervisory Circuit
中文描述： 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDIP16
封裝： 0.300 INCH, PLASTIC, DIP-16
文件頁(yè)數(shù)： 9/16頁(yè)
文件大?。?/td> 295K
代理商： LTC1235CN
9
LTC1235
Voltage Output
During normal operation, the LTC1235 uses a charge
pumped NMOS power switch to achieve low dropout and
low supply current. This power switch can deliver up to
50mA to V
OUT
from V
CC
and has a typical on resistance of
5
. The V
OUT
pin should be bypassed with a capacitor of
0.1
μ
F or greater to ensure stability. Use of a larger bypass
capacitor is advantageous for supplying current to heavy
transient loads.
When operating currents larger than 50mA are required
from V
OUT
, or a lower dropout (V
CC
- V
OUT
voltage differ-
ential) is desired, the LTC1235 provides BATT ON output
to drive the base of external PNP transistor (Figure 3).
Another alternative to provide higher current is to connect
a high current Schottky diode from the V
CC
pin to the V
OUT
pin to supply the extra current.
The LTC1235 is protected for safe area operation with
short circuit limit. Output current is limited to approxi-
mately 200mA. If the device is overloaded for a long period
of time, thermal shutdown turns the power switch off until
the device cools down. The threshold temperature for
thermal shutdown is approximately 155
°
C with about
10
°
C of hysteresis which prevents the device from oscil-
lating in and out of shutdown.
The PNP switch was not chosen for the internal power
switch because it injects unwanted current into the sub-
strate. This current is collected by the V
BATT
pin in com-
petitive devices and adds to the charging current of the
battery which can damage lithium batteries. LTC1235
uses a charge pumped NMOS power switch to eliminate
unwanted charging current while achieving low dropout
and low supply current. Since no current goes to the
substrate, the current collected by V
BATT
pin is strictly
junction leakage.
Conditional Battery Backup
LTC1235 provides an unique feature to either allow V
OUT
to be switched to V
BATT
or to disable the CMOS RAM
battery backup function when primary power is lost.
Disabling the battery backup function is useful in conserv-
ing the backup battery's life when the SRAM doesn't need
battery backup during long term storage of a computer
system, or delivery of the computer system to the end
user.
The BACKUP pin (Pin 8) is used to serve this feature on
power-down. When V
CC
is falling through the reset voltage
threshold, the status of the BACKUP pin (logic low or logic
high) is stored in the Memory Logic (see BLOCK DIA-
GRAM). If the stored status is logic high and V
CC
fall to
50mV greater than V
BATT
, a 125
PMOS switch, M2,
connects the V
BATT
input to V
OUT
and the battery switchover
comparator, C2, shuts off the NMOS power switch, M1.
M2 is designed for very low dropout voltage (input-to-
output differential). This feature is advantageous for low
current applications such as battery backup in CMOS RAM
and other low power CMOS circuitry. If the stored status
is logic low and V
CC
falls to 50mV greater than V
BATT
, the
Memory Logic keeps M2 off and C2 shuts off M1. V
OUT
is
in Battery Saving Mode (see Figure 4). The supply current
in both mode is 1
μ
A maximum.
On power-ups, C2 keeps M1 off before V
CC
reaches 70mV
higher than V
BATT
. On the first power-up after the battery
is replaced (with power off), the status stored in the
Memory Logic is undetermined. V
OUT
could be either in
Battery Backup Mode or in Battery Saving Mode. When
V
CC
is 70mV greater than V
BATT
, M1 connects V
OUT
to V
CC
.
C2 has typically 20mV of hysteresis to prevent spurious
switching when V
CC
remains nearly equal to V
BATT
and the
status stored in the Memory Logic is high. The response
time of C2 is approximately 20
μ
s.
Figure 3. Using BATT ON to Drive External PNP Transistor
+5V
+3V
0.1
μ
F
0.1
μ
F
V
BATT
V
CC
LTC1235
V
OUT
GND
ANY PNP POWER TRANSISTOR
LTC1235 F03
BATT ON
R1
U
S
A
O
PPLICATI
U
U
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LTC1235CSW 功能描述:IC MPU SUPERVISRY CIRCUIT 16SOIC RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 監(jiān)控器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類(lèi)型:簡(jiǎn)單復(fù)位/加電復(fù)位 監(jiān)視電壓數(shù)目:1 輸出:開(kāi)路漏極或開(kāi)路集電極 復(fù)位:高有效 復(fù)位超時(shí):- 電壓 - 閥值:1.8V 工作溫度:-40°C ~ 125°C 安裝類(lèi)型:表面貼裝 封裝/外殼:6-TSOP（0.059"，1.50mm 寬）5 引線 供應(yīng)商設(shè)備封裝:5-TSOP 包裝:剪切帶 (CT) 其它名稱(chēng):NCP301HSN18T1GOSCT
LTC1235CSW#PBF 功能描述:IC MPU SUPERVISRY CIRCUIT 16SOIC RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 監(jiān)控器 系列:- 其它有關(guān)文件:STM6905 View All Specifications 標(biāo)準(zhǔn)包裝:1 系列:- 類(lèi)型:多壓監(jiān)控器 監(jiān)視電壓數(shù)目:5 輸出:開(kāi)路漏極或開(kāi)路集電極 復(fù)位:低有效 復(fù)位超時(shí):最小為 140 ms 電壓 - 閥值:2.188V，2.955V，可調(diào)，可調(diào)，可調(diào) 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:8-TSSOP，8-MSOP（0.118"，3.00mm 寬） 供應(yīng)商設(shè)備封裝:8-TSSOP 包裝:Digi-Reel® 產(chǎn)品目錄頁(yè)面:1197 (CN2011-ZH PDF) 其它名稱(chēng):497-8728-6
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