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参数资料
| 型号： | LTC3736EUF-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 825kHz |
| 占空比： | 100% |
| 电源电压： | 2.75 V ~ 9.8 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： | 24-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3736-1
APPLICATIO S I FOR ATIO
Operating Frequency
When spread spectrum operation is enabled (SSDIS =
GND), the frequency of the LTC3736-1 is randomly varied
over the range of frequencies between 450kHz and 580kHz.
In this case, a capacitor (1nF to 4.7nF) should be connected
Inductor Value Calculation
Given the desired input and output voltages, the inductor
value and operating frequency f OSC directly determine the
inductor’s peak-to-peak ripple current:
V IN ? f OSC ? L ?
betweentheFREQpinandSGND(orV IN )tosmoothoutthe
changes in frequency. This not only provides a smoother
frequency spectrum but also ensures that the switching
I RIPPLE =
V OUT ? V IN – V OUT ?
? ?
regulator remains stable by preventing abrupt changes
in frequency. A value of 2200pF is suitable in most
applications.
When the spread spectrum operation is disabled (SSDIS =
V IN ), the LTC3736-1’s frequency may be selected from
among three discrete, constant frequencies using the FREQ
pin. Floating the FREQ pin selects 550kHz operation; tying
this pin to V IN selects 750kHz, while tying this pin to GND
selects 300kHz. Table 2 summarizes the different states in
which the FREQ pin can be used.
Table 2
Lower ripple current reduces core losses in the inductor,
ESR losses in the output capacitors, and output voltage
ripple. Thus, highest efficiency operation is obtained at
low frequency with a small ripple current. Achieving this,
however, requires a large inductor.
A reasonable starting point is to choose a ripple current
that is about 40% of I OUT(MAX) . Note that the largest ripple
current occurs at the highest input voltage. To guarantee
that ripple current does not exceed a specified maximum,
the inductor should be chosen according to:
? OUT
FREQ PIN
0V
SSDIS PIN
V IN
FREQUENCY
300kHz
L ≥
V IN – V OUT
f OSC ? I RIPPLE
V
V IN
Floating
V IN
550kHz
V IN
Capacitor to GND
or V IN
V IN
GND
750kHz
Spread Spectrum (450kHz to 580kHz)
Inductor Core Selection
Once the inductance value is determined, the type of
inductor must be selected. High efficiency converters
Note that when spread spectrum operation is disabled, the
LTC3736-1 operates like the standard, constant frequency
LTC3736, except that at light loads, the LTC3736-1 oper-
ates in pulse skipping mode. This mode is not available on
the LTC3736 unless the device is synchronized to an ex-
ternal clock signal using its phase-locked loop (PLL). Thus,
if an LTC3736 with pulse skipping function is needed, then
the LTC3736-1 with spread spectrum disabled is the appro-
priate solution. Table 3 summarizes the key differences in
the available features on the LTC3736 and LTC3736-1.
generally cannot afford the core loss found in low cost
powdered iron cores, forcing the use of ferrite, molyper-
malloy or Kool M μ ? cores. Actual core loss is independent
of core size for a fixed inductor value, but it is very
dependent on inductance selected. As inductance in-
creases, core losses go down. Unfortunately, increased
inductance requires more turns of wire and therefore
copper losses will increase.
Ferrite designs have very low core loss and are preferred
at high switching frequencies, so design goals can
Burst Mode
Table 3
AVAILABLE FEATURES/OPTIONS
Selectable Constant Frequency
Spread Spectrum
Synchronizable (PLL)
?
Forced Continuous Mode
Pulse Skipping Mode
LTC3736
Yes
No
Yes
Yes
Yes
When Synchronized
LTC3736-1
Yes
Yes
No
No
No
Yes
concentrate on copper loss and preventing saturation.
Ferrite core material saturates “hard,” which means that
inductance collapses abruptly when the peak design cur-
rent is exceeded. This results in an abrupt increase in
inductor ripple current and consequent output voltage
ripple. Do not allow the core to saturate!
Burst Mode is a registered trademark of Linear Technology Corporation.
Kool M μ is a registered trademark of Magnetics, Inc.
37361f
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3736EUF-2 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Sync Step Down 2.75V to 9.8V Input 24-Pin QFN EP |
| LTC3736EUF-2#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 24-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 |
| LTC3736EUF-2#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 24-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 |
| LTC3737EGN | 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:PolyPhase® 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) |
| LTC3737EGN#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:PolyPhase® 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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