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参数资料
| 型号： | LTC3826IUH#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 32-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 585kHz |
| 占空比： | 99.4% |
| 电源电压： | 4 V ~ 36 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： | 32-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3826
APPLICATIONS INFORMATION
R SENSE Selection for Output Current
R SENSE is chosen based on the required output current.
The current comparator has a maximum threshold of
100mV/R SENSE and an input common mode range of
SGND to 10V. 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, Δ I L .
Allowing a margin for variations in the IC and external
component values yields:
Inductor Value Calculation
The operating frequency and inductor selection are inter-
related in that higher operating frequencies allow the use
of smaller inductor and capacitor values. So why would
anyone ever choose to operate at lower frequencies with
larger components? The answer is ef?ciency. A higher
frequency generally results in lower ef?ciency because
of MOSFET gate charge losses. In addition to this basic
trade-off, the effect of inductor value on ripple current and
low current operation must also be considered.
R SENSE =
80mV
I MAX
The inductor value has a direct effect on ripple current.
The inductor ripple current Δ I L decreases with higher
inductance or frequency and increases with higher V IN :
V OUT 1 – OUT
Whenusingthecontrollerinverylowdropoutconditions,
the maximum output current level will be reduced due to the
internal compensation required to meet stability criterion
I L =
1
(f)(L)
V
V IN
for buck regulators operating at greater than 50% duty
factor. A curve is provided in the Typical Performance Char-
acteristics section to estimate this reduction in peak output
current level depending upon the operating duty factor.
Operating Frequency and Synchronization
The choice of operating frequency, is a trade-off between
ef?ciency and component size. Low frequency operation
improves ef?ciency by reducing MOSFET switching losses,
both gate charge loss and transition loss. However, lower
frequency operation requires more inductance for a given
amount of ripple current.
The internal oscillator for each of the LTC3826’s controllers
runs at a nominal 390kHz frequency when the PLLLPF pin
is left ?oating and the PLLIN/MODE pin is a DC low or high.
Pulling the PLLLPF to INTV CC selects 530kHz operation;
pulling the PLLLPF to SGND selects 250kHz operation.
Alternatively, the LTC3826 will phase-lock to a clock
signal applied to the PLLIN/MODE pin with a frequency
between 140kHz and 650kHz (see Phase-Locked Loop
and Frequency Synchronization).
Accepting larger values of Δ I L allows the use of low
inductances, but results in higher output voltage ripple
and greater core losses. A reasonable starting point for
setting ripple current is Δ I L = 0.3(I MAX ). The maximum
Δ I L occurs at the maximum input voltage.
The inductor value also has secondary effects. The tran-
sition to Burst Mode operation begins when the average
inductor current required results in a peak current below
10% of the current limit determined by R SENSE . Lower
inductor values (higher Δ I L ) will cause this to occur at
lower load currents, which can cause a dip in ef?ciency in
the upper range of low current operation. In Burst Mode
operation, lower inductance values will cause the burst
frequency to decrease.
Inductor Core Selection
Once the value for L is known, the type of inductor must
be selected. High ef?ciency converters generally cannot
afford the core loss found in low cost powdered iron cores,
forcing the use of more expensive ferrite or molypermalloy
cores. Actual core loss is independent of core size for a
?xed inductor value, but it is very dependent on inductance
3826fc
16
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| LTC3827EG-1 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Sync Step Down 4V to 36V Input 28-Pin SSOP |
| LTC3827EG-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-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:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3827EG-1#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-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: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 |
| LTC3827EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-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:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
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