參數(shù)資料
型號(hào)： LTC1698EGN
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： Isolated Secondary Synchronous Rectifier Controller
中文描述： SWITCHING CONTROLLER, PDSO16
封裝： 0.150 INCH, PLASTIC, SSOP-16
文件頁(yè)數(shù)： 9/24頁(yè)
文件大小： 1047K
代理商： LTC1698EGN
9
LTC1698
1698f
catch MOSFETs Q3 and Q4 are off. As soon as transistors
Q1 and Q2 turn on, the flux in the power transformer T1
forces the body diodes of Q3 and Q4 to conduct, and the
whole circuit starts like a conventional forward converter.
At the same time, the LTC1698 V
DD
potential ramps up
quickly through the V
DD
bias circuitry. Once the V
DD
voltage exceeds 4.0V, the LTC1698 enables its drivers and
enters synchronous operation.
The pulse transformer T2 synchronizes the primary and
secondary MOSFET drivers. In a typical conversion cycle,
the primary MOSFETs Q1 and Q2 turn on simultaneously.
SG goes low and generates a negative spike at the LTC1698
SYNC input through the pulse transformer. The LTC1698
forces FG to turn on and CG to turn off. Power is delivered
to the load through the transformer T1 and the inductor L1.
At the beginning of the next phase in which Q1 and Q2 turn
off, SG goes high, SYNC sees a positive spike, the MOSFET
Q3 shuts off, Q4 conducts and allows continuous current
to flow through the inductor L1. The capacitor C
OUT
filters
the switching waveform to provide a steady DC output
voltage for the load.
The LTC1698 error amplifier ERR senses the output volt-
age through an external resistor divider and regulates the
V
FB
pin potential to the 1.233V internal bandgap voltage.
An external RC network across the V
FB
and V
COMP
pins
frequency compensates the error amplifier feedback. The
opto driver amplifies the voltage difference between the
V
COMP
pin and the bandgap potential, driving the external
optocoupler diode with an inverting gain of 5. The
optocoupler feeds the amplified output error signal to the
primary controller and closes the forward converter volt-
age feedback loop. Under start-up conditions, the internal
diode across the LTC1698 error amplifier clamps the
V
COMP
pin. This speeds up the opto driver recovery time by
reducing the negative slew rate excursion at the COMP pin.
The forward converter output voltage can be easily ad-
justed. The potential at the MARGIN pin is capable of
forcing the error amplifier reference voltage to move
linearly by
±
5%. The internal R
MARGIN
resistor converts
the MARGIN voltage to a current and linearly controls the
offset of the error amplifier. Connecting the MARGIN pin
to 3.3V increases the V
FB
voltage by 5%, and connecting
the MARGIN pin to 0V reduces V
FB
by 5%. With the
MARGIN pin floating, the VFB voltage is regulated to the
internal bandgap voltage.
The current limit transconductance amplifier I
LIM
provides
the secondary side average current limit function. The
average voltage drops across the R
SECSEN
resistor is
sensed and compared to the –25mV threshold set by the
internal I
LIM
amplifier. Once I
LIM
detects high output
current, the current amplifier output pulls high, overrides
the error amplifier, injects more current into the photo
diode and forces a lower duty cycle. An RC network
connected to the I
COMP
pin is used to stabilize the second-
ary current limit loop. Alternatively, if only overcurrent
fault protection is required, I
COMP
can float.
If under abnormal conditions the feedback path is broken,
OVPIN provides another route for overvoltage fault pro-
tection. If the voltage at OVPIN is higher than the bandgap
voltage, the OVP comparator forces OPTODRV high im-
mediately. A simple external RC filter prevents a momen-
tary overshoot at OVPIN from triggering the OVP
comparator. Short OVPIN to ground if this pin is not used.
The LTC1698 provides an open-drain PWRGD output. If
V
FB
is less than 94% of its nominal value for more than
1ms, the PWRGD comparator pulls the PWRGD pin low.
If V
FB
is higher than 94% of its nominal value for more than
2ms, the transistor M
PWRGD
shuts off, and an external
resistor pulls the PWRGD pin high.
The LTC1698 provides an auxiliary 3.3V logic power
supply. This auxiliary power supply is externally compen-
sated with a minimum 0.1
μ
F bypass capacitor. It supplies
up to 10mA of current to any external devices.
OPERATIOU
(Refer to Block Diagram)
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1698EGN#PBF 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX
LTC1698EGN#TR 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX
LTC1698EGN#TRPBF 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX
LTC1698ES 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無(wú) 升壓:是 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR)
LTC1698ES#PBF 功能描述:IC REG CTRLR ISO PWM CM 16-SOIC RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無(wú) 升壓:是 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR)
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