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| 型号： | LTC3714EG#TR |
| 厂商： | Linear Technology |
| 文件页数： | 20/28页 |
| 文件大小： | 0K |
| 描述： | IC STP-DWN CNTRLR W/OPAMP 28SSOP |
| 标准包装： | 2,000 |
| 应用： | 控制器，Intel Pentium? |
| 输入电压： | 4 V ~ 36 V |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 1.75 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 28-SSOP |
| 包装： | 带卷 (TR) |
| 其它名称： | LTC3714EGTR |
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LTC3714
APPLICATIONS INFORMATION
R ON =
= 330k
L =
? 1 ?
? = 0.6μH
Δ I L =
? 1 –
? = 5.4A
EfficiencyConsiderations
The percent efficiency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
what is limiting the efficiency and which change would
produce the most improvement. Although all dissipative
elements in the circuit produce losses, four main sources
account for most of the losses in LTC3714 circuits:
1. DC I 2 R losses. These arise from the resistances of
the MOSFETs, inductor and PC board traces and
cause the efficiency to drop at high output currents.
In continuous mode the average output current flows
through L, but is chopped between the top and bottom
MOSFETs. If the two MOSFETs have approximately the
same R DS(ON) , then the resistance of one MOSFET can
simply be summed with the resistances of L and the
board traces to obtain the DC I 2 R loss. For example, if
R DS(ON) = 0.01Ω and R L = 0.005Ω, the loss will range
from 15mW up to 1.5W as the output current varies
from 1A to 10A for a 1.5V output.
2. Transition loss. This loss arises from the brief amount
of time the top MOSFET spends in the saturated region
during switch node transitions. It depends upon the
input voltage, load current, driver strength and MOSFET
capacitance, among other factors. The loss is significant
at input voltages above 20V and can be estimated from:
Transition Loss ? (1.7A –1 ) V IN2 I OUT C RSS f
3. INTV CC current. This is the sum of the MOSFET driver
and control currents. This loss can be reduced by sup-
plying INTV CC current through the EXTV CC pin from a
high efficiency source, such as an output derived boost
network or alternate supply if available.
4. C IN loss. The input capacitor has the difficult job of
filtering the large RMS input current to the regulator. It
must have a very low ESR to minimize the AC I 2 R loss
and sufficient capacitance to prevent the RMS current
from causing additional upstream losses in fuses or
batteries.
Other losses, including C OUT ESR loss, Schottky diode
D1 conduction loss during dead time and inductor core
loss generally account for less than 2% additional loss.
When making any adjustments to improve efficiency, the
final arbiter is the total input current for the regulator at
your operating point. If you make a change and the input
current decreases, then you improved the efficiency. If
there is no change in input current, then there is no change
in efficiency.
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, V OUT immediately shifts by an amount
equal to ?I LOAD ? (ESR), where ESR is the effective series
resistance of C OUT . ?I LOAD also begins to charge or dis-
charge C OUT generating a feedback error signal used by the
regulator to return V OUT to its steady-state value. During
this recovery time, V OUT can be monitored for overshoot
or ringing that would indicate a stability problem. The I TH
pin external components shown in Figure 8 will provide
adequate compensation for most applications. For a
detailed explanation of switching control loop theory see
Linear Technology Application Note 76.
Design Example
As a design example, take a supply with the follow-
ing specifications: V IN = 7V to 24V (15V nominal),
V OUT = 1.15V ±100mV, I OUT(MAX) = 15A, f = 300kHz. First,
calculate the timing resistor with V ON = V OUT :
1
( 300kHz ) ( 10pF )
and choose the inductor for about 40% ripple current at
the maximum V IN :
1.15V ? 1.15V ?
( 300kHz ) ( 0.4 ) ( 15A ) ? 24V ?
Choosing a standard value of 0.68μH results in a maximum
ripple current of:
1.15V ? 1.15V ?
( 300kHz ) ( 0.68μH ) ? 24V ?
3714f
20
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| LTC3716EG | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 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) |
| LTC3716EG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-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: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) |
| LTC3716EG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 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 |
| LTC3716EG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-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: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) |
| LTC3717-1#PBF | 制造商:LINEAR 功能描述: 制造商:Linear Technology 功能描述: |
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