參數(shù)資料
型號(hào)： LT3485EDD-0#TR
廠商： LINEAR TECHNOLOGY CORP
元件分類： 模擬信號(hào)調(diào)理
英文描述： SPECIALTY ANALOG CIRCUIT, PDSO10
封裝： 3 X 3 MM, PLASTIC, MO-229WEED-2, DFN-10
文件頁(yè)數(shù)： 20/20頁(yè)
文件大?。?/td> 339K
代理商： LT3485EDD-0#TR
LT3485-0/LT3485-1/
LT3485-2/LT3485-3
9
34850123fb
CHARGE pin low. Only when the final output voltage is
reached will the DONE pin go low. Figure 2 shows these
various modes in action. When CHARGE is first brought
high, charging commences. When CHARGE is brought
low during charging, the part goes into shutdown and
VOUT no longer rises. When CHARGE is brought high
again, charging resumes. When the target VOUT voltage is
reached, the DONE pin goes low and charging stops.
Finally the CHARGE pin is brought low again so the part
enters shutdown and the DONE pin goes high.
Both VBAT and VIN have undervoltage lockout (UVLO).
When one of these pins goes below its UVLO voltage, the
DONE pin goes low. With an insufficient bypass capacitor
on VBAT or VIN, the ripple on the pin is likely to activate
UVLO and terminate the charge. The applications circuits
in the data sheet suggest values adequate for most
applications.
The LT3485 VMONT pin functions as an output to a
microcontroller to communicate the progress of the charge.
The VMONT pin starts to function at about 0.2V, which
corresponds to 64V with a turns ratio of 10.2. When the
VMONT pin is at 1V, the DONE pin goes low and the
charging terminates. The pin’s output is only valid when
the part is charging.
The LT3485 also integrates an IGBT drive. The IGBTPWR
pin supplies the power. The IGBT output goes high when
IGBTIN goes high and conversely goes low when IGBTIN
goes low. While IGBTIN is low, the IGBT drive draws no
quiescent current from IGBTPWR.
OPERATIO
U
The LT3485-0/LT3485-1/LT3485-2/LT3485-3 are designed
to charge photoflash capacitors quickly and efficiently. The
operation of the part can be best understood by referring
to Figure 1. When the CHARGE pin is first driven high, a one
shot sets both SR latches in the correct state. The power
NPN device, Q1, turns on and current begins ramping up
in the primary of transformer T1. Comparator A1 monitors
the switch current and when the peak current reaches 2A
(LT3485-3), 1.4A (LT3485-0), 1A (LT3485-2) or 0.7A
(LT3485-1), Q1 is turned off. Since T1 is utilized as a flyback
transformer, the flyback pulse on the SW pin will cause the
output of A3 to be high. The voltage on the SW pin needs
to be at least 45mV higher than VBAT for this to happen.
During this phase, current is delivered to the photoflash
capacitor via the secondary and diode D1. As the second-
ary current decreases to zero, the SW pin voltage will begin
to collapse. When the SW pin voltage drops to 45mV above
VBAT or lower, the output of A3 (DCM Comparator) will go
low. This fires a one shot which turns Q1 back on. This cycle
will continue to deliver power to the output.
Output voltage detection is accomplished via R2, R1, Q2,
and comparator A2 (VOUT Comparator). Resistors R1 and
R2 are sized so that when the SW voltage is 31.5V above
VBAT, the output of A2 goes high which resets the master
latch. This disables Q1 and halts power delivery. NPN
transistor Q3 is turned on pulling the DONE pin low,
indicating that the part has finished charging. Power
delivery can only be restarted by toggling the CHARGE pin.
The CHARGE pin gives full control of the part to the user.
The charging can be halted at any time by bringing the
Figure 2. Halting the Charging Cycle with the CHARGE Pin
LT3485-2
VIN = 3.6V
COUT = 50F
VOUT
100V/DIV
VCHARGE
5V/DIV
VDONE
5V/DIV
1s/DIV
3485 F02
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT3485EDD-1 制造商:LINER 制造商全稱:Linear Technology 功能描述:Photoflash Capacitor Chargers with Output Voltage Monitor and Integrated IGBT Drive
LT3485EDD-1#PBF 功能描述:IC CHARGER PHOTOFLASH 10-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
LT3485EDD-1#TRPBF 功能描述:IC CHARGER PHOTOFLASH 10-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
LT3485EDD-2 制造商:LINER 制造商全稱:Linear Technology 功能描述:Photoflash Capacitor Chargers with Output Voltage Monitor and Integrated IGBT Drive
LT3485EDD-2#PBF 功能描述:IC CHARGER PHOTOFLASH 10-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電源管理 - 專用 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 應(yīng)用:手持/移動(dòng)設(shè)備 電流 - 電源:- 電源電壓:3 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:14-LLP-EP（4x4） 包裝:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名稱:LP3905SD-30DKR
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