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参数资料
| 型号： | LTC3778EF#TR |
| 厂商： | Linear Technology |
| 文件页数： | 14/24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 |
| 电源电压： | 4 V ~ 36 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 ~ 85°C |
| 封装/外壳： | 20-TSSOP（0.173"，4.40mm 宽） |
| 包装： | 带卷 (TR) |
| 其它名称： | LTC3778EFTR |
LTC3778
APPLICATIO S I FOR ATIO
V IN
+
V IN
C IN
1N4148
To further limit current in the event of a short circuit to
ground, the LTC3778 includes foldback current limiting. If
the output falls by more than 50%, then the maximum
OPTIONAL
EXTV CC
CONNECTION
5V < V OUT2 < 7V
R4
LTC3778
EXTV CC
FCB
TG
SW
T1
1:N
? +
+
V OUT2
C SEC
1 μ F
V OUT1
C OUT
sense voltage is progressively lowered to about one sixth
of its full value.
Minimum Off-time and Dropout Operation
R3
BG
The minimum off-time t OFF(MIN) is the smallest amount of
SGND
PGND
3778 F04
time that the LTC3778 is capable of turning on the bottom
MOSFET, tripping the current comparator and turning the
Figure 4. Secondary Output Loop and EXTV CC Connection
Fault Conditions: Current Limit and Foldback
The maximum inductor current is inherently limited in a
current mode controller by the maximum sense voltage. In
MOSFET back off. This time is generally about 250ns. The
minimum off-time limit imposes a maximum duty cycle of
t ON /(t ON + t OFF(MIN) ). If the maximum duty cycle is reached,
due to a dropping input voltage for example, then the
output will drop out of regulation. The minimum input
voltage to avoid dropout is:
the LTC3778, the maximum sense voltage is controlled by
the voltage on the V RNG pin. With valley current control,
the maximum sense voltage and the sense resistance
determine the maximum allowed inductor valley current.
V IN ( MIN ) = V OUT
t ON + t OFF (MIN)
t ON
I LIMIT =
+ ? I L
The corresponding output current limit is:
V SNS ( MAX ) 1
( R DS ( ON ) ρ T )* 2
The current limit value should be checked to ensure that
I LIMIT(MIN) > I OUT(MAX) . The minimum value of current limit
generally occurs with the lowest V IN at the highest ambient
temperature. Note that it is important to check for self-
consistency between the assumed MOSFET junction tem-
perature and the resulting value of I LIMIT which heats the
MOSFET switches.
Caution should be used when setting the current limit
based upon the R DS(ON) of the MOSFETs. The maximum
current limit is determined by the minimum MOSFET on-
resistance. Data sheets typically specify nominal and
maximum values for R DS(ON) , but not a minimum. A
reasonable assumption is that the minimum R DS(ON) lies
the same amount below the typical value as the maximum
lies above it. Consult the MOSFET manufacturer for further
guidelines.
*Use R SENSE value here if a sense resistor is connected between SENSE + and SENSE –
.
14
INTV CC Regulator
An internal P-channel low dropout regulator produces the
5V supply that powers the drivers and internal circuitry
within the LTC3778. The INTV CC pin can supply up to
50mA RMS and must be bypassed to ground with a
minimum of 4.7 μ F tantalum or other low ESR capacitor.
Good bypassing is necessary to supply the high transient
currents required by the MOSFET gate drivers. Applica-
tions using large MOSFETs with a high input voltage and
high frequency of operation may cause the LTC3778 to
exceed its maximum junction temperature rating or RMS
current rating. Most of the supply current drives the
MOSFET gates unless an external EXTV CC source is used.
In continuous mode operation, this current is I GATECHG =
f(Q g(TOP) + Q g(BOT) ). The junction temperature can be
estimated from the equations given in Note 2 of the
Electrical Characteristics. For example, the LTC3778EF is
limited to less than 15mA from a 30V supply:
T J = 70 ° C + (15mA)(30V)(110 ° C/W) = 120 ° C
For larger currents, consider using an external supply with
the DRV CC pin.
3778f
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相关代理商/技术参数 |
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| LTC3780EG | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP |
| LTC3780EG#PBF | 功能描述:IC REG CTRLR BST PWM CM 24-SSOP 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 |
| LTC3780EG#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP T/R |
| LTC3780EG#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 24-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 |
| LTC3780EGPBF | 制造商:Linear Technology 功能描述:4-Switch Buck-Boost Controller SSOP24 |
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