参数资料
| 型号： | ADP1621ARMZ-R7 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 18/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 10-MSOP |
| 标准包装： | 1 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1.5MHz |
| 占空比： | 97% |
| 电源电压： | 2.9 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 倍增器： | 是 |
| 除法器： | 是 |
| Cuk： | 是 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 标准包装 |
| 产品目录页面： | 791 (CN2011-ZH PDF) |
| 配用： | ADP1621-EVALZ-ND - BOARD EVALUATION FOR ADP1621 |
| 其它名称： | ADP1621ARMZ-R7DKR |
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R CS × ( V OUT + V D ? V IN ) × ( 1 ? t OFF , MIN × f SW )
? V COMP , CLAMP ? V COMP , ZCT I SC , PK × R S × D ?
? n 1 ? t OFF , MIN × f SW V IN × D ?
2 × f SW × L ?
?
?
?
?
?
V COMP , CLAMP ? V COMP , ZCT I SC , PK × R S × D
n 1 ? t OFF , MIN × f SW
I L , PK =
V IN × D × ( 1 ? D )
I LOAD < (37)
ADP1621
R DSON , of the external power MOSFET. Otherwise, R CS
represents the external current-sense resistor.
Solving for R S gives the slope-compensation criterion:
R S > (34)
2 × I SC , PK × f SW × L
Keep in mind that the above inequality is a function of both
ADP1621 parameters and off-chip components, the values of
which vary from part to part and with temperature. Select R S to
ensure current-loop stability for all possible variations.
After accounting for parameter variations, use values of R S that
are as close to the calculated limit as possible because excessive
slope compensation reduces the benefits of current-mode control
and increases the “softness” of the current limit, as discussed in the
current of 70 μA, R S should not exceed 1.6 k? because the voltage
at the CS pin is typically clamped at 116 mV. It is also recom-
mended that R S be greater than 20 ?. If the calculated R S is greater
than 1.6 k?, the parameters in Equation 34, such as R CS , f SW , and L,
can be adjusted such that R S is less than 1.6 k?.
In conclusion, the value of R S should be 20 ? ≤ R S ≤ 1.6 k?.
CURRENT LIMIT
The current limit in the ADP1621 limits the peak inductor
current and is achieved by the COMP voltage clamp. The peak
inductor current, I L,PK , is given by
?
(35)
R CS
where V COMP,CLAMP is the COMP clamp voltage (typically 2.0 V),
V COMP,ZCT is the COMP zero-current threshold (typically 1.0 V),
n is the current-sense amplifier gain (typically 9.5), I SC,PK is the
peak slope-compensation current (typically 70 μA), R S is the
slope-compensation resistor, D is the duty cycle, f SW is the
switching frequency, t OFF,MIN is the minimum off time (typically
190 ns), and R CS is the current-sense resistor. In the case of
lossless current sensing, R CS is equal to the on resistance, R DSON ,
of the external power MOSFET. Otherwise, R CS represents the
external current-sense resistor.
The current limit in the ADP1621 is a “soft” current limit.
When the inductor current reaches the I L,PK limit given in
Equation 35, the duty cycle decreases, and the output voltage
drops below the desired voltage. The I L,PK limit in Equation 35
then increases in response to the smaller duty cycle, D. The
larger the slope-compensation resistor, R S , the larger the effect
on I L,PK for an incremental decrease in D. This behavior results
in a “soft” current limit for the ADP1621. Use values of R S that are
as close as possible to the calculated limit derived from
Equation 34. If high-precision current limiting is required,
consider inserting a fuse in series with the inductor.
Also, keep in mind that the current limit is a function of both
ADP1621 parameters and off-chip components, the values of
Data Sheet
which vary from part to part and with temperature. If lossless
current sensing is used, consider that the on resistance of a
MOSFET typically increases with increasing junction temperature.
The peak inductor current limit also limits the maximum load
current at a given output voltage. The maximum load current,
assuming CCM operation, is given by
I LOAD , MAX = ( 1 ? D ) ×
? ? ?
?
R CS
? ?
(36)
If the load current exceeds I LOAD,MAX , the output voltage drops
below the desired voltage.
LIGHT LOAD OPERATION
Discontinuous Conduction Mode
With light loads, the average inductor current is small, and,
depending on the converter design, the instantaneous inductor
current may reach 0 during the time when the MOSFET is off.
This mode of operation is termed discontinuous conduction
mode. The condition for entering discontinuous conduction
mode in a boost converter is
2 × L × f SW
When the instantaneous inductor current reaches 0 during the
cycle, the inductor ceases to be a current source, and ringing
can be observed in the waveforms of the MOSFET drain voltage
and the inductor current. The frequency of the ringing is the
resonant frequency of the inductor and the total capacitance
from the SW node to GND, which includes the capacitances of
the MOSFET and diode, and any parasitic capacitances from
the PCB. While adding a resistive element, such as a snubber, to
the system further dampens the resonance, it also decreases the
efficiency of the regulator.
Pulse-Skipping Modulation
The ADP1621 features circuitry that improves the converter
efficiency and minimizes power consumption with no load or
very light loads. When the COMP voltage drops below V COMP,ZCT
(typically 1.0 V), which can occur at sufficiently light loads, the
MOSFET is powered off until the FB voltage drops below 1.215 V.
Then, the error amplifier drives the COMP voltage higher, and
the converter resumes switching when the COMP voltage rises
above the V COMP,ZCT voltage. While the MOSFET is powered off,
the output capacitor supplies current to the load.
With light loads, the COMP voltage hovers around 1.0 V, and
short periods of switching are followed by long periods of the
MOSFET being powered off. This pulse-skipping modulation
operation improves converter efficiency by reducing the number of
switching cycles and therefore reducing the gate drive current and
the switching transition power loss.
Rev. B | Page 18 of 32
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADP1621-BL2-EVZ | 制造商:Analog Devices 功能描述:BLANK ADISIMPOWER EVAL ADP1621 - Boxed Product (Development Kits) |
| ADP1621-BL4-EVZ | 功能描述:BOARD EVALUATION FOR ADP1621 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 标准包装:1 系列:- 主要目的:DC/DC，步降 输出及类型:1，非隔离 功率 - 输出:- 输出电压:3.3V 电流 - 输出:3A 输入电压:4.5 V ~ 28 V 稳压器拓扑结构:降压 频率 - 开关:250kHz 板类型:完全填充 已供物品:板 已用 IC / 零件:L7981 其它名称:497-12113STEVAL-ISA094V1-ND |
| ADP1621-EVAL | 制造商:AD 制造商全称:Analog Devices 功能描述:Constant-Frequency, Current-Mode Step-Up DC/DC Controller |
| ADP1621-EVALZ | 功能描述:BOARD EVALUATION FOR ADP1621 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 标准包装:1 系列:- 主要目的:DC/DC，步降 输出及类型:1，非隔离 功率 - 输出:- 输出电压:3.3V 电流 - 输出:3A 输入电压:4.5 V ~ 28 V 稳压器拓扑结构:降压 频率 - 开关:250kHz 板类型:完全填充 已供物品:板 已用 IC / 零件:L7981 其它名称:497-12113STEVAL-ISA094V1-ND |
| ADP162ACBZ-1.2-R7 | 功能描述:IC REG LDO 1.2V .15A 4WLCSP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 系列:- 其它有关文件:LD39015JXX12 View All Specifications 标准包装:1 系列:- 稳压器拓扑结构:正，固定式 输出电压:1.2V 输入电压:1.5 V ~ 5.5 V 电压 - 压降（标准）:- 稳压器数量:1 电流 - 输出:150mA 电流 - 限制（最小）:- 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:4-WFBGA，FCBGA 供应商设备封装:4-覆晶（1.07x1.07） 包装:Digi-Reel® 其它名称:497-11958-6 |
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