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参数资料
| 型号： | LTC3829EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/40页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 850kHz |
| 占空比： | 94% |
| 电源电压： | 4.5 V ~ 38 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： | 38-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3829
APPLICATIONS INFORMATION
R SENSE =
I MAX +
TheTypicalApplicationonthefirstpageofthisdatasheet
is a basic LTC3829 application circuit. The LTC3829 can be
configured to use either DCR (inductor resistance) sens-
ing or low value resistor sensing. The choice between the
two current sensing schemes is largely a design trade-off
between cost, power consumption and accuracy. DCR
sensing is becoming popular because it saves expensive
current sensing resistors and is more power efficient,
especially in high current applications. However, current
sensing resistors provide the most accurate current limits
for the controller. Other external component selection is
driven by the load requirement, and begins with the se-
lection of R SENSE (if R SENSE is used) and inductor value.
Next, the power MOSFETs are selected. Finally, input and
output capacitors are selected.
Current Limit Programming
The I LIM pin is a tri-level logic input which sets the maxi-
mum current limit of the controller. When I LIM is either
grounded, floated or tied to INTV CC , the typical value for
the maximum current sense threshold will be 30mV, 50mV
or 75mV, respectively.
Which setting should be used? For the best current limit
accuracy, use the 75mV setting. The 30mV setting will allow
for the use of very low DCR inductors or sense resistors,
but at the expense of current limit accuracy. The 50mV
setting is a good balance between the two.
SENSE + and SENSE – Pins
The SENSE + and SENSE – pins are the inputs to the current
comparators. The common mode input voltage range of
the current comparators is 0V to 5V. All SENSE + pins are
high impedance inputs with small currents of less than
1μA. The high impedance inputs to the current compara-
tors allow accurate DCR sensing. All SENSE – pins and
DIFFP should be connected to V OUT directly when DCR
sensing is used. Care must be taken not to float these
pins during normal operation. Filter components mutual
to the sense lines should be placed close to the LTC3829,
and the sense lines should run close together to a Kelvin
connection underneath the current sense element (shown
in Figure 1). Sensing current elsewhere can effectively add
parasitic inductance and capacitance to the current sense
element, degrading the information at the sense terminals
and making the programmed current limit unpredictable.
If DCR sensing is used (Figure 2b), sense resistor R1
should be placed close to the switching node, to prevent
noise from coupling into sensitive small-signal nodes. The
capacitor C1 should be placed close to the IC pins.
TO SENSE FILTER,
NEXT TO THE CONTROLLER
C OUT
3829 F01
R SENSE
Figure 1. Sense Lines Placement with Sense Resistor
Low Value Resistors Current Sensing
A typical sensing circuit using a discrete resistor is shown
in Figure 2a. R SENSE is chosen based on the required
output current. The current comparator has a maximum
threshold V SENSE(MAX) determined by the I LIM setting. The
input common mode range of the current comparator is
0V to 5V. The current comparator threshold sets the peak
of the inductor current, yielding a maximum average
output current I MAX equal to the peak value less half the
peak-to-peak ripple current, ? I L . To calculate the sense
resistor value, use the equation:
V SENSE(MAX)
? I L
2
Because of possible PCB noise in the current sensing
loop, the AC current sensing ripple of ? V SENSE = ? I L ?
R SENSE also needs to be checked in the design to get a
good signal-to-noise ratio. In general, for a reasonably
good PCB layout, a 10mV ? V SENSE voltage is recom-
mended as a conservative number to start with, either
for R SENSE or DCR sensing applications. For previous
generation current mode controllers, the maximum sense
voltage was high enough (e.g., 75mV for the LTC1628/
LTC3728 family) that the voltage drop across the parasitic
inductance of the sense resistor represented a relatively
small error. For today’s highest current density solutions,
however, the value of the sense resistor can be less than
3829fa
14
For more information www.linear.com/LTC3829
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| LTC3829IFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3829IFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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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| LTC3829IUHF#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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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