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参数资料
| 型号： | ADP1874-0.6-EVALZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 23/44页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR ADP1874 |
| 标准包装： | 1 |
| 系列： | * |
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Data Sheet
ADP1874/ADP1875
As soon as the forward current through the lower side MOSFET
decreases to a level where
10 mV = I Q2 × R ON(Q2)
the zero-cross comparator (or I REV comparator) emits a signal to
turn off the lower side MOSFET. From this point, the slope of the
t ON
C
SW
INFORMATION
VREG
I
V IN
as the body diode of the lower side MOSFET begins to conduct
current and continues conducting current until the remaining
energy stored in the inductor has been depleted.
R (TRIMMED)
Figure 77. Constant On-Time Time
SW
ANOTHER t ON EDGE IS
TRIGGERED WHEN V OUT
FALLS BELOW REGULATION
t ON
The constant on-time (t ON ) is not strictly constant because it
varies with V IN and V OUT . However, this variation occurs in such
a way as to keep the switching frequency virtually independent
of V IN and V OUT .
The t ON timer uses a feedforward technique, which when applied
to the constant on-time control loop makes it a pseudo-fixed
LS
I LOAD
0A
HS AND LS
IN IDLE MODE
ZERO-CROSS COMPARATOR
DETECTS 10mV OFFSET AND
TURNS OFF LS
10mV = R ON × I LOAD
frequency to a first-order approximation. Second-order effects,
such as dc losses in the external power MOSFETs (see the
Efficiency Consideration section), cause some variation in
frequency vs. load current and line voltage. These effects are
shown in Figure 23 to Figure 34. The variations in frequency
are much reduced compared with the variations generated if
the feedforward technique is not used.
The feedforward technique establishes the following relationship:
f SW =
Figure 76. 10 mV Offset to Ensure Prevention of Negative Inductor Current
The system remains in idle mode until the output voltage drops
below regulation. A PWM pulse is then produced, turning on the
upper side MOSFET to maintain system regulation. The ADP1875
does not have an internal clock, so it switches purely as a hysteretic
controller as described in this section.
TIMER OPERATION
The ADP1874 / ADP1875 employ a constant on-time architecture,
which provides a variety of benefits, including improved load
and line transient response when compared with a constant
(fixed) frequency current-mode control loop of comparable
loop design. The constant on-time timer, or t ON timer, senses
the high-side input voltage (V IN ) and the output voltage (V OUT )
using SW waveform information to produce an adjustable one-
shot PWM pulse. The pulse varies the on-time of the upper side
MOSFET in response to dynamic changes in input voltage,
1
K
where f SW is the controller switching frequency (300 kHz,
600 kHz, and 1.0 MHz).
The t ON timer senses V IN and V OUT to minimize frequency variation
as previously explained. This provides pseudo-fixed frequency
as explained in the Pseudo-Fixed Frequency section. To allow
headroom for V IN and V OUT sensing, adhere to the following
equations:
VREG ≥ V IN /8 + 1.5
VREG ≥ V OUT /4
For typical applications where VREG is 5 V, these equations are not
relevant; however, care may be required for lower VREG/VIN
inputs.
t ON = K × OUT
output voltage, and load current conditions to maintain output
regulation. The timer generates an on-time (t ON ) pulse that is
inversely proportional to V IN .
V
V IN
where K is a constant that is trimmed using an RC timer product
for the 300 kHz, 600 kHz, and 1.0 MHz frequency options.
Rev. A | Page 23 of 44
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADP1874-1.0-EVALZ | 功能描述:BOARD EVAL FOR ADP1874 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:* 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ADP1874ARQZ-0.3-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| ADP1874ARQZ-0.6-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:是 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) |
| ADP1874ARQZ-1.0-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:是 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) |
| ADP1875 | 制造商:AD 制造商全称:Analog Devices 功能描述:Synchronous Buck Controller with Constant On-Time and Valley Current Mode |
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