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参数资料
| 型号： | LTC1436ACGN-PLL#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 21/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-SSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 138kHz |
| 占空比： | 99% |
| 电源电压： | 3.5 V ~ 30 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： | 0°C ~ 70°C |
| 封装/外壳： | 24-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
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LTC1436A
LTC1436A-PLL/LTC1437A
APPLICATIO N S I N FOR M ATIO N
Efficiency. For example, in a 20V to 5V application,
INDUCTOR
L
1435A F08
Figure 13. Allowable Inductor/R SENSE Layout Orientations
Efficiency Considerations
The 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. Efficiency can be expressed as:
Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percentage
of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of the
losses in LTC1436A/LTC1437A circuits: LTC1436A/
LTC1437A V IN current, INTV CC current, I 2 R losses and
topside MOSFET transition losses.
1. The V IN current is the DC supply current given in the
Electrical Characteristics table which excludes MOSFET
driver and control currents. V IN current results in a
small (< 1%) loss which increases with V IN .
2. INTV CC current is the sum of the MOSFET driver and
control currents. The MOSFET driver current results
from switching the gate capacitance of the power
MOSFETs. Each time a MOSFET gate is switched from
low to high to low again, a packet of charge dQ moves
from INTV CC to ground. The resulting dQ/dt is a current
out of INTV CC that is typically much larger than the
control circuit current. In continuous mode, I GATECHG =
f(Q T + Q B ), where Q T and Q B are the gate charges of the
topside and bottom side MOSFETs. It is for this reason
that the Adaptive Power output stage switches to a low
Q T MOSFET during low current operation.
By powering EXTV CC from an output-derived source,
the additional V IN current resulting from the driver and
control currents will be scaled by a factor of Duty Cycle/
10mA of INTV CC current results in approximately 3mA
of V IN current. This reduces the midcurrent loss from
10% or more (if the driver was powered directly from
V IN ) to only a few percent.
3. I 2 R losses are predicted from the DC resistances of the
MOSFET, inductor and current shunt. In continuous
mode the average output current flows through L and
R SENSE , but is “chopped” between the topside main
MOSFET and the synchronous MOSFET. 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 R SENSE to obtain I 2 R
losses. For example, if each R DS(ON) = 0.05 ? ,
R L = 0.15 ? and R SENSE = 0.05 ? , then the total resis-
tance is 0.25 ? . This results in losses ranging from 3%
to 10% as the output current increases from 0.5A to 2A.
I 2 R losses cause the efficiency to drop at high output
currents.
4. Transition losses apply only to the topside MOSFET(s),
and only when operating at high input voltages (typi-
cally 20V or greater). Transition losses can be esti-
mated from:
Transition Loss = 2.5(V IN ) 1.85 (I MAX )(C RSS )(f)
Other losses including C IN and C OUT ESR dissipative
losses, Schottky conduction losses during dead-time and
inductor core losses, generally account for less than 2%
total additional loss.
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 DC (resistive) 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 discharge C OUT which generates a feedback
error signal. The regulator loop then acts to return V OUT to
its steady-state value. During this recovery time V OUT can
be monitored for overshoot or ringing, which would
indicate a stability problem. The I TH external components
shown in the Figure 1 circuit will provide adequate com-
pensation for most applications.
14367afb
21
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| LTC1436AEGN#PBF | 功能描述:IC REG CTRLR BUCK 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:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1436AEGN#TRPBF | 功能描述:IC REG CTRLR BUCK 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:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1436AIGN | 功能描述:IC REG CTRLR BUCK PWM CM 24-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 |
| LTC1436AIGN#PBF | 功能描述:IC REG CTRLR BUCK 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 |
| LTC1436AIGN#TR | 功能描述:IC REG CTRLR BUCK PWM CM 24-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 |
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