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参数资料
| 型号： | LTC1735CGN-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 335kHz |
| 占空比： | 99.4% |
| 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 ~ 85°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
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LTC1735-1
APPLICATIO S I FOR ATIO
Table 1
and control currents. V IN current results in a small
PGOOD PIN
DC Voltage: 0V to 0.7V
Resistor Pull-Up to
INT VCC (or Other DC
Voltage Less Than INTV CC )
Resistor to Ext Clock:
(0V to 1.5V)
CONDITION
No Power Good Indication
Burst Mode Operation Disabled/Forced
Continuous Current Reversal Enabled
Power Good Indication
Burst Mode, No Current Reversal
When Power is Good
No Power Good Indication
Burst Mode Operation Disabled
(< 0.1%) loss that 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
No Current Reversal
The circuit shown in Figure 7 provides a power good
output and forces continuous operation. Transistor Q1
keeps the voltage at the PGOOD pin below 0.8V thus
disabling Burst Mode operation. When the window com-
parator indicates the output voltage is not within its 7.5%
window, the base of Q1 is pulled to ground and the power
good output appearing at the collector of Q2 goes low.
INTV CC
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.
By powering EXTV CC from an output-derived source (or
other high efficiency source), the additional V IN current
resulting from the driver and control currents will be
scaled by a factor of (Duty Cycle)/(Efficiency). For
example, in a 15V to 1.8V application, 10mA of INTV CC
current results in approximately 1.2mA of V IN current.
470k
100k
10k
This reduces the midcurrent loss from 10% or more (if
PGOOD
PIN 4
Q1
Q2
POWER
GOOD
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
1735-1 F07
Figure 7. Forced Continuous Operation with Power Good Indication
Efficiency Considerations
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. Percent efficiency can be
expressed as:
%Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc., are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of the
losses in LTC1735-1 circuits: 1) LTC1735-1 V IN current,
2) INTV CC current, 3) I 2 R losses, 4) Topside MOSFET
transition losses.
1. The V IN current is the DC supply current given in the
electrical characteristics which excludes MOSFET driver
MOSFETs, 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) = 0.02 ? , R L =
0.03 ? , and R SENSE = 0.01 ? , then the total resistance is
0.06 ? . This results in losses ranging from 3% to 17%
as the output current increases from 1A to 5A for a 1.8V
output, or 4% to 20% for a 1.5V output. Efficiency
varies as the inverse square of V OUT for the same
external components and power level. 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 become significant when operating at high
input voltages (typically 12V or greater). Transition
losses can be estimated from:
Transition Loss = (1.7) V IN2 I O(MAX) C RSS f
19
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| LTC1735CGNPBF | 制造商:Linear Technology 功能描述:Regulator Synch Step Down LTC1735CGN |
| LTC1735CS | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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) |
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| LTC1735CS#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC 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) |
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