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| 型号： | LTC3858EUH-2#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | DUAL SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封装： | 5 X 5 MM, LEAD FREE, PLASTIC, MO-220WHHD, QFN-32 |
| 文件页数： | 3/40页 |
| 文件大小： | 432K |
| 代理商： | LTC3858EUH-2#TRPBF |
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LTC3858-2
11
38582f
Table 1. Summary of the Differences Between LTC3858, LTC3858-1 and LTC3858-2
LTC3858
LTC3858-1
LTC3858-2
Short-Circuit Latchoff Feature?
Yes, But Can Be Defeated
Not Present
Overvoltage Protection
BG Forced On
(Bottom MOSFET “Crowbar”)
BG Forced On
(Bottom MOSFET “Crowbar”)
BG Not Forced On
(Behavior Depends on Light Load Mode)
Optional Tracking Start-Up?
No
Yes
Independent PGOOD1 and PGOOD2 Pins?
Yes
No, PGOOD1 Only
Yes
CLKOUT/PHASMD Pins for PolyPhase
Yes
No
Yes
Adjustable Current Limit (ILIM Pin)
Yes
No
Yes
Package
5mm × 5mm QFN
4mm × 5mm QFN and
Narrow SSOP
5mm × 5mm QFN
OPERATION (Refer to the Functional Diagram)
Table 1 summarizes the differences between the LTC3858-2
and its sister parts, the LTC3858 and LTC3858-1. The
LTC3858-2 uses a constant frequency, current mode
step-down architecture with the two controller channels
operating 180 degrees out of phase. During normal op-
eration, each external top MOSFET is turned on when the
clock for that channel sets the RS latch, and is turned off
when the main current comparator, ICMP, resets the RS
latch. The peak inductor current at which ICMP trips and
resets the latch is controlled by the voltage on the ITH pin,
which is the output of the error amplifier, EA. The error
amplifier compares the output voltage feedback signal at
the VFB pin (which is generated with an external resistor
divider connected across the output voltage, VOUT, to
ground) to the internal 0.800V reference voltage. When the
load current increases, it causes a slight decrease in VFB
relative to the reference, which causes the EA to increase
the ITH voltage until the average inductor current matches
the new load current.
After the top MOSFET is turned off each cycle, the bottom
MOSFET is turned on until either the inductor current starts
to reverse, as indicated by the current comparator IR, or
the beginning of the next clock cycle.
INTVCC/EXTVCC Power
Power for the top and bottom MOSFET drivers and most
other internal circuitry is derived from the INTVCCpin.When
the EXTVCC pin is left open or tied to a voltage less than
4.7V, the VIN LDO (low dropout linear regulator) supplies
5.1V from VIN to INTVCC. If EXTVCC is taken above 4.7V,
the VIN LDO is turned off and the EXTVCC LDO is turned
on. Once enabled, the EXTVCC LDO supplies 5.1V from
EXTVCC to INTVCC. Using the EXTVCC pin allows the INTVCC
power to be derived from a high efficiency external source
such as one of the LTC3858-2 switching regulator outputs.
Each top MOSFET driver is biased from the floating boot-
strap capacitor, CB, which normally recharges during each
switching cycle through an external diode when the top
MOSFET turns off. If the input voltage, VIN, decreases to
a voltage close to VOUT, the loop may enter dropout and
attempt to turn on the top MOSFET continuously. The
dropout detector detects this and forces the top MOSFET
off for about one-twelfth of the clock period every tenth
cycle to allow CB to recharge.
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相关代理商/技术参数 |
参数描述 |
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| LTC3858IGN-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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