參數(shù)資料
型號(hào)： 1977IFE
廠(chǎng)商： Linear Technology Corporation
英文描述： High Voltage 1.5A, 500kHz Step-Down Switching Regulator with 100uA Quiescent Current
中文描述： 高電壓，500kHz降壓1.5安培的電流型開(kāi)關(guān)穩(wěn)壓器的靜態(tài)電流為100uA
文件頁(yè)數(shù)： 17/24頁(yè)
文件大?。?/td> 288K
代理商： 1977IFE
LT1977
17
1977f
APPLICATIOU
W
U
U
must weigh the importance of each specification in choos-
ing the best diode for the application.
The use of so-called “ultrafast” recovery diodes is gener-
ally not recommended. When operating in continuous
mode, the reverse recovery time exhibited by “ultrafast”
diodes will result in a slingshot type effect. The power
internal switch will ramp up V
IN
current into the diode in an
attempt to get it to recover. Then, when the diode has
finally turned off, some tens of nanoseconds later, the V
SW
node voltage ramps up at an extremely high dV/dt, per-
haps 5V to even 10V/ns! With real world lead inductances
the V
SW
node can easily overshoot the V
IN
rail. This can
result in poor RFI behavior and, if the overshoot is severe
enough, damage the IC itself.
BOOST PIN
For most applications the boost components are a 0.1
μ
F
capacitor and a MMSD914 diode. The anode is typically
connected to the regulated output voltage to generate a
voltage approximately V
OUT
above V
IN
to drive the output
stage (Figure 7a). However, the output stage discharges
the boost capacitor during the on time of the switch. The
output driver requires at least 2.5V of headroom through-
out this period to keep the switch fully saturated. If the
output voltage is less than 3.3V it is recommended that an
alternate boost supply is used. The boost diode can be
connected to the input (Figure 7b) but care must be taken
to prevent the boost voltage (V
BOOST
= V
IN
2) from
exceeding the BOOST pin absolute maximum rating. The
additional voltage across the switch driver also increases
power loss and reduces efficiency. If available, an inde-
pendent supply can be used to generate the required
BOOST voltage (Figure 7c). Tying BOOST to V
IN
or an
independent supply may reduce efficiency but it will re-
duce the minimum V
IN
required to start-up with light
loads. If the generated BOOST voltage dissipates too
much power at maximum load, the BOOST voltage the
LT1977 sees can be reduced by placing a Zener diode in
series with the BOOST diode (Figure 7a option).
A 0.1
μ
F boost capacitor is recommended for most appli-
cations. Almost any type of film or ceramic capacitor is
suitable but the ESR should be <1
to ensure it can be fully
recharged during the off time of the switch. The capacitor
value is derived from worst-case conditions of 1800ns on
time, 40mA boost current and 0.7V discharge ripple. The
boost capacitor value could be reduced under less de-
manding conditions but this will not improve circuit opera-
tion or efficiency. Under low input voltage and low load
conditions a higher value capacitor will reduce discharge
ripple and improve start-up operation.
SHUTDOWN FUNCTION AND UNDERVOLTAGE
LOCKOUT
The SHDN pin on the LT1977 controls the operation of the
IC. When the voltage on the SHDN pin is below the 1.2V
shutdown threshold the LT1977 is placed in a “zero”
supply current state. Driving the SHDN pin above the
shutdown threshold enables normal operation. The SHDN
pin has an internal sink current of 3
μ
A.
BOOST
LT1977
GND
V
BOOST
– V
= V
OUT
V
BOOST(MAX)
= V
IN
+ V
OUT
V
IN
V
OUT
OPTIONAL
(7a)
V
IN
SW
BOOST
LT1977
GND
V
BOOST
– V
= V
V
BOOST(MAX)
= V
DC
+ V
IN
V
IN
V
DC
D
SS
1977 F07
V
OUT
(7c)
V
IN
SW
BOOST
LT1977
GND
V
BOOST
– V
SW
= V
IN
V
BOOST(MAX)
= 2V
IN
V
IN
V
OUT
(7b)
V
IN
SW
Figure 7. BOOST Pin Configurations
相關(guān)PDF資料
PDF描述
1982995-1 Pluggable Bus Bar Connectors & Sockets
19MT050XF FULL BRIDGE FREDFET MTP HEXFET POWER MOSFET
19TQ015S SCHOTTKY RECTIFIER
19U200PG1K Pressure Sensors Low-Cost, Stainless Steel, Isolated Sensors
19U050PA4K Pressure Sensors Low-Cost, Stainless Steel, Isolated Sensors
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
1977-XX-XXX 制造商:BOURNS 制造商全稱(chēng):Bourns Electronic Solutions 功能描述:1977 Series High Frequency Coaxial SPD
1978 功能描述:電池組 RECHARGEABLE BATTRY PACK RoHS:否 制造商:Ultralife 電池大小: 電池?cái)?shù)量: 輸出電壓:3.7 V 容量: 化學(xué)性質(zhì):Lithium 端接類(lèi)型:Wire
19780 功能描述:KIT METER RES DIG TEMP/HUMIDITY RoHS:否 類(lèi)別:靜電控制，ESD，無(wú)塵室產(chǎn)品 >> 監(jiān)視器，測(cè)試儀 系列:- 產(chǎn)品目錄繪圖:19226 標(biāo)準(zhǔn)包裝:1 系列:- 類(lèi)型:工作站監(jiān)視器 使用:工作面，腕帶監(jiān)視 特點(diǎn):連續(xù)監(jiān)視，NIST 可追溯，單芯系統(tǒng) 電源類(lèi)型:AC 適配器 包括:AC 適配器，證書(shū)，軟線(xiàn)，五金件 其它名稱(chēng):16-1116
19-780 制造商:GC Electronics 功能描述:Squeeze Bottle Dispense Solvents In The Required Amounts In The Proper Location
1978000000 制造商:Weidmuller 功能描述:SC-SMT 3.81/09/135G 1.5SN BK
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠(chǎng)商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*