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| 型号： | LTC3838IFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 28/54页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38TSSOP |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 2MHz |
| 电源电压： | 4.5 V ~ 38 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： | 38-TFSOP （0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3838
APPLICATIONS INFORMATION
and BOOST capacitor under all operating conditions. Vari-
able frequency in response to load steps offers superior
transient performance but requires higher instantaneous
gate drive. Gate charge demands are greatest in high
frequency low duty factor applications under high load
steps and at start-up.
DRV CC Regulator and EXTV CC Power
The LTC3838 features a PMOS low dropout (LDO) linear
regulator that supplies power to DRV CC from the V IN supply.
The LDO regulates its output at the DRV CC1 pin to 5.3V.
The LDO can supply a maximum current of 100mA and
must be bypassed to ground with a minimum of 4.7μF
ceramic capacitor. Good bypassing is needed to supply
the high transient currents required by the MOSFET gate
drivers and to minimize interaction between the channels.
High input voltage applications in which large MOSFETs
are being driven at high frequencies may cause the maxi-
mum junction temperature rating for the LTC3838 to be
exceeded, especially if the LDO is active and provides
DRV CC . Power dissipation for the IC in this case is high-
est and is approximately equal to V IN ? I DRVCC . The gate
charge current is dependent on operating frequency as
discussed in the Efficiency Considerations section. The
junction temperature can be estimated by using the equa-
tion given in Note 2 of the Electrical Characteristics. For
example, when using the LDO, LTC3838’s DRV CC current
is limited to less than 52mA from a 38V supply at T A =
70°C in the FE package:
T J = 70°C + (52mA)(38V)(28°C/W) = 125°C
To prevent the maximum junction temperature from being
exceeded, the input supply current must be checked while
operating in continuous conduction mode at maximum V IN .
When the voltage applied to the EXTV CC pin rises above
the switchover voltage (typically 4.6V), the V IN LDO is
turned off and the EXTV CC is connected to DRV CC2 pin with
an internal switch. This switch remains on as long as the
voltage applied to EXTV CC remains above the hysteresis
be derived from the LTC3838’s switching regulator output
V OUT during normal operation and from the LDO when the
output is out of regulation (e.g., start up, short circuit). If
more current is required through the EXTV CC than is speci-
fied, an external Schottky diode can be added between the
EXTV CC and DRV CC pins. Do not apply more than 6V to the
EXTV CC pin and make sure that EXTV CC is less than V IN .
Significant efficiency and thermal gains can be realized
by powering DRV CC from the switching converter output,
since the V IN current resulting from the driver and control
currents will be scaled by a factor of (Duty Cycle)/(Switcher
Efficiency).
Tying the EXTV CC pin to a 5V supply reduces the junction
temperature in the previous example from 125°C to:
T J = 70°C + (52mA)(5V)(28°C/W) = 77°C
However, for 3.3V and other low voltage outputs, ad-
ditional circuitry is required to derive DRV CC power from
the converter output.
The following list summarizes the four possible connec-
tions for EXTV CC :
1. EXTV CC left open (or grounded). This will cause INTV CC
to be powered from the internal 5.3V LDO resulting
in an efficiency penalty of up to 10% at high input
voltages.
2. EXTV CC connected directly to switching converter output
V OUT is higher than the switchover voltage’s higher limit
(4.8V). This provides the highest efficiency.
3. EXTV CC connected to an external supply. If a 4.8V or
greater external supply is available, it may be used to
power EXTV CC providing that the external supply is
sufficient for MOSFET gate drive requirements.
4. EXTV CC connected to an output-derived boost network.
For 3.3V and other low voltage converters, efficiency
gains can still be realized by connecting EXTV CC to an
output-derived voltage that has been boosted to greater
than 4.8V.
(around 200mV) below the switchover voltage. Using
EXTV CC allows the MOSFET driver and control power to
3838fa
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3838IUHF#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3838IUHF#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3838IUHF-1#PBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 38QFN 制造商:Linear Technology 功能描述:BUCK DUAL CNTRL 4.5-38V 2MHZ 38QFN 制造商:Linear Technology 功能描述:BUCK, DUAL, CNTRL, 4.5-38V, 2MHZ, 38QFN 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual, Fast, Accurate Step-Down Controller with Differential 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, DUAL, BUCK, ADJ, QFN-38, Primary Input Voltage:38V, No. of Outputs:2, Output Current:25A, No. of Pins:38, Operating Temperature Min:-40C, Operating Temperature Max:125C, MSL:MSL 1 - Unlimited , RoHS Compliant: Yes |
| LTC3838IUHF-1#TRPBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 38QFN 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual, Fast, Accurate Step-Down Controller with Differential 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, DUAL, BUCK, ADJ, QFN-38, Primary Input Voltage:38V, No. of Outputs:2, Output Current:25A, No. of Pins:38, Operating Temperature Min:-40C, Operating Temperature Max:125C, MSL:MSL 1 - Unlimited , RoHS Compliant: Yes |
| LTC3838IUHF-2#PBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN 制造商:Linear Technology 功能描述:BUCK DUAL CNTRL 4.5-38V 2MHZ 38QFN 制造商:Linear Technology 功能描述:DC-DC CONTROLLER BUCK 2MHZ QFN-38 制造商:Linear Technology 功能描述:BUCK, DUAL, CNTRL, 4.5-38V, 2MHZ, 38QFN 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Dual, Fast, Accurate Step-Down Controller with Differential |
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