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参数资料
| 型号： | LTC3891EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 20/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 20TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 835kHz |
| 占空比： | 99% |
| 电源电压： | 4 V ~ 60 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： | 20-TSSOP（0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3891
APPLICATIONS INFORMATION
INTV CC Regulators
The LTC3891 features two separate internal P-channel
low dropout linear regulators (LDO) that supply power
at the INTV CC pin from either the V IN supply pin or the
EXTV CC pin depending on the connection of the EXTV CC
pin. INTV CC powers the gate drivers and much of the
LTC3891’s internal circuitry. The V IN LDO and the EXTV CC
LDO regulate INTV CC to 5.1V. Each of these can supply a
peak current of at least 50mA and must be bypassed to
ground with a minimum of 2.2μF ceramic capacitor. No
matter what type of bulk capacitor is used, an additional
1μF ceramic capacitor placed directly adjacent to the INTV CC
and PGND pins is highly recommended. Good bypassing
is needed to supply the high transient currents required
by the MOSFET gate drivers and to prevent interaction
between the channels.
High input voltage applications in which large MOSFETs are
being driven at high frequencies may cause the maximum
junction temperature rating for the LTC3891 to be exceeded.
The INTV CC current, which is dominated by the gate charge
current, may be supplied by either the V IN LDO or the
EXTV CC LDO. When the voltage on the EXTV CC pin is less
than 4.7V, the V IN LDO is enabled. Power dissipation for the
IC in this case is highest and is equal to V IN ? I INTVCC . 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
equations given in Note 3 of the Electrical Characteristics.
For example, the LTC3891 INTV CC current is limited to less
than 32mA from a 40V supply when not using the EXTV CC
supply at a 70°C ambient temperature:
T J = 70°C + (32mA)(40V)(43°C/W for QFN) = 125°C
To prevent the maximum junction temperature from be-
ing exceeded, the input supply current must be checked
while operating in forced continuous mode (PLLIN/MODE
= INTV CC ) at maximum V IN .
When the voltage applied to EXTV CC rises above 4.7V, the
V IN LDO is turned off and the EXTV CC LDO is enabled. The
EXTV CC LDO remains on as long as the voltage applied to
EXTV CC remains above 4.5V. The EXTV CC LDO attempts
to regulate the INTV CC voltage to 5.1V, so while EXTV CC
is less than 5.1V, the LDO is in dropout and the INTV CC
voltage is approximately equal to EXTV CC . When EXTV CC
is greater than 5.1V, up to an absolute maximum of 14V,
INTV CC is regulated to 5.1V.
Using the EXTV CC LDO allows the MOSFET driver and control
power to be derived from one of the LTC3891’s switching
regulator outputs (4.7V ≤ V OUT ≤ 14V) during normal
operation and from the V IN LDO when the output is out of
regulation (e.g., start-up, short-circuit). If more current
is required through the EXTV CC LDO than is specified, an
external Schottky diode can be added between the EXTV CC
and INTV CC pins. In this case, do not apply more than 6V
to the EXTV CC pin and make sure that EXTV CC ≤ V IN .
Significant efficiency and thermal gains can be realized by
powering INTV CC from the output, since the V IN current
resulting from the driver and control currents will be scaled
by a factor of (Duty Cycle)/(Switcher Efficiency).
For 5V to 14V regulator outputs, this means connecting
the EXTV CC pin directly to V OUT . Tying the EXTV CC pin to
an 8.5V supply reduces the junction temperature in the
previous example from 125°C to:
T J = 70°C + (32mA)(8.5V)(43°C/W) = 82°C
However, for 3.3V and other low voltage outputs, addi-
tional circuitry is required to derive INTV CC power from
the output.
The following list summarizes the four possible connec-
tions for EXTV CC :
1. EXTV CC Grounded. This will cause INTV CC to be powered
from the internal 5.1V regulator resulting in an efficiency
penalty of up to 10% at high input voltages.
2. EXTV CC Connected Directly to V OUT . This is the normal
connection for a 5V to 14V regulator and provides the
highest efficiency.
3. EXTV CC Connected to an External Supply. If an external
supply is available in the 5V to 14V range, it may be
used to power EXTV CC providing it is compatible with
the MOSFET gate drive requirements. Ensure that
EXTV CC < V IN .
3891fa
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| LTC3891EUDC#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3891EUDC#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 900kHz QFN20 |
| LTC3891EUDC#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 20-QFN 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: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) |
| LTC3891HFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP 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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