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參數(shù)資料
| 型號(hào)： | ADP1875ARQZ-0.3-R7 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 300 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | ROHS COMPLIANT, MO-137AB, QSOP-16 |
| 文件頁數(shù)： | 16/44頁 |
| 文件大小： | 2475K |
| 代理商： | ADP1875ARQZ-0.3-R7 |
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ADP1874/ADP1875
Rev. 0 | Page 23 of 44
As soon as the forward current through the lower-side MOSFET
decreases to a level where
10 mV = IQ2 × RON(Q2)
the zero-cross comparator (or IREV comparator) emits a signal to
turn off the lower-side MOSFET. From this point, the slope of the
inductor current ramping down becomes steeper (see Figure 76)
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.
HS AND LS
IN IDLE MODE
10mV = RON × ILOAD
ZERO-CROSS COMPARATOR
DETECTS 10mV OFFSET AND
TURNS OFF LS
SW
LS
0A
ILOAD
tON
ANOTHER
tON EDGE IS
TRIGGERED WHEN VOUT
FALLS BELOW REGULATION
09
34
7-
07
4
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 tON timer, senses
the high-side input voltage (VIN) and the output voltage (VOUT)
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,
output voltage, and load current conditions to maintain output
regulation. The timer generates an on-time (tON) pulse that is
inversely proportional to VIN.
IN
OUT
ON
V
K
t
×
=
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.
C
R (TRIMMED)
VREG
tON
VIN
I
SW
INFORMATION
09
34
7-
0
75
Figure 77. Constant On-Time Time
The constant on-time (tON) is not strictly constant because it
varies with VIN and VOUT. However, this variation occurs in such
a way as to keep the switching frequency virtually independent
of VIN and VOUT.
The tON timer uses a feedforward technique, which when applied
to the constant on-time control loop makes it a pseudo-fixed
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:
K
f
SW
1
=
where fSW is the controller switching frequency (300 kHz,
600 kHz, and 1.0 MHz).
The tON timer senses VIN and VOUT to minimize frequency variation
as previously explained. This provides pseudo-fixed frequency
as explained in the Pseudo-Fixed Frequency section. To allow
headroom for VIN and VOUT sensing, adhere to the following
equations:
VREG ≥ VIN/8 + 1.5
VREG ≥ VOUT/4
For typical applications where VREG is 5 V, these equations are not
relevant; however, care may be required for lower VREG/VIN
inputs.
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| ADP1875ARQZ-1.0-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| ADP1876 | 制造商:AD 制造商全稱:Analog Devices 功能描述:600 kHz Dual Output Synchronous Buck |
| ADP1876ACPZ-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 32LFCSP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| ADP1876-EVALZ | 功能描述:BOARD EVAL FOR ADP1876 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評(píng)估板 - DC/DC 與 AC/DC（離線）SMPS 系列:* 標(biāo)準(zhǔn)包裝:1 系列:- 主要目的:DC/DC，步降 輸出及類型:1，非隔離 功率 - 輸出:- 輸出電壓:3.3V 電流 - 輸出:3A 輸入電壓:4.5 V ~ 28 V 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):降壓 頻率 - 開關(guān):250kHz 板類型:完全填充 已供物品:板 已用 IC / 零件:L7981 其它名稱:497-12113STEVAL-ISA094V1-ND |
| ADP1877 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Dual Output Synchronous Buck PWM Controller With Tracking |
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