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参数资料
| 型号： | LTC3812EFE-5 |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, PDSO16 |
| 封装： | 4.40 MM, PLASTIC, TSSOP-16 |
| 文件页数： | 14/32页 |
| 文件大小： | 425K |
| 代理商： | LTC3812EFE-5 |
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LTC3812-5
21
38125fb
to boost this voltage above 4.7V. In this mode, EXTVCC is
grounded and the NMOS is chosen to handle the worst-
case power dissipation:
PMOSFET = (VIN(MAX))[(f)(QG(TOP) + QG(BOTTOM) + 3mA]
To operate properly, the fault timeout operation must be
disabled by choosing
RNDRV > (VIN(MAX) – 5.5V – VT)/270μA
If the required RNDRV value results in an unacceptable
value for VIN(MIN) (see Equation 1), fault timeout operation
can also be disabled by connecting a 500k to 1M resistor
from RUN/SS to INTVCC.
Using Trickle Charge Mode
Trickle charge mode is selected by shorting NDRV and
INTVCCandconnectingEXTVCCtoVOUT.Tricklechargemode
has the advantage of not requiring an external MOSFET but
takes longer to start up due to slow charge up of CINTVCC
through RPULLUP (tDELAY = 0.77 RPULLUP CINTVCC) and
usually requires a larger INTVCC capacitor value to hold
up the supply voltage during start-up. Once the INTVCC
voltage reaches the trickle charge UV threshold of 9V, the
drivers will turn on and start discharging CINTVCC at a rate
determined by the driver current IG. In order to ensure
proper start-up, CINTVCC must be chosen large enough so
that the EXTVCC voltage reaches the switchover threshold
of 4.7V before CINTVCC discharges below the falling UV
threshold of 4V. This is ensured if:
CINTVCC >IG Larger of
COUT
IMAX
or
5.5 10
5 C
SS
VOUT(REG)
where IGisthegatedrivecurrent=(f)(QG(TOP)+QG(BOTTOM))
and IMAX is the maximum inductor current selected by
VRNG.
For RPULLUP, the value should fall in the following range
to ensure proper start-up:
Min RPULLUP > (VIN(MAX) – 14V)/ICCSR
Max RPULLUP < (VIN(MIN) – 9V)/IQ,SHUTDOWN
Using an External Supply Connected to the INTVCC
If an external supply is available between 4.2V and 14V,
the supply can be connected directly to the INTVCC pins.
In this mode, INTVCC, EXTVCC and NDRV must be shorted
together.
INTVCC Supply and the EXTVCC Connection
The LTC3812-5 contains an internal low dropout regula-
tor to produce the 5.5V INTVCC supply from the EXTVCC
pin voltage. This regulator turns on when the EXTVCC pin
is above 4.7V and remains on until EXTVCC drops below
4.45V. This allows the IC/MOSFET power to be derived
from the output or an output derived boost network during
normal operation and from the external NMOS from VIN
during start-up or short-circuit. Using the EXTVCC pin in
this way results in signicant efciency gains compared
to what would be possible when deriving this power
continuously from the typically much higher VIN voltage.
The EXTVCC connection also allows the power supply to
be congured in trickle charge mode in which it starts up
with a high-valued “bleed” resistor connected from VIN
to INTVCC to charge up the INTVCC capacitor. As soon as
the output rises above 4.7V the internal EXTVCC regulator
takes over before the INTVCC capacitor discharges below
the UV threshold. When the EXTVCC regulator is active,
the EXTVCC pin can supply up to 50mA RMS. Do not ap-
ply more than 15V to the EXTVCC pin. The following list
summarizes the possible connections for EXTVCC:
1. EXTVCC grounded. This connection will require INTVCC
to be powered continuously from an external NMOS
from VIN resulting in an efciency penalty as high as
10% at high input voltages.
2. EXTVCC connected directly to VOUT. This is the normal
connection for 4.7V < VOUT < 15V and provides the
highest efciency. The power supply will start up using
an external NMOS or a bleed resistor until the output
supply is available.
3. EXTVCC connected to an output-derived boost network.
If VOUT < 4.7V. The low voltage output can be boosted
using a charge pump or yback winding to greater than
4.7V.
4. EXTVCC connected to INTVCC. This is the required
connection for EXTVCC if INTVCC is connected to an
external supply where the external supply is 4.2V <
VEXT < 14V.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3812EFE5#PBF | 制造商:Linear Technology 功能描述: |
| LTC3812EFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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 |
| LTC3812EFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
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