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參數(shù)資料
| 型號： | MAX8884YEREKE+T |
| 廠商： | Maxim Integrated |
| 文件頁數(shù)： | 10/17頁 |
| 文件大?。?/td> | 579K |
| 描述： | IC REG TRPL BCK/LINEAR 16UCSP |
| 產(chǎn)品培訓(xùn)模塊： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 標(biāo)準(zhǔn)包裝： | 2,500 |
| 拓?fù)洌?/td> | 降壓（降壓）同步（1），線性（LDO）（2） |
| 功能： | 任何功能 |
| 輸出數(shù)： | 3 |
| 頻率 - 開關(guān)： | 2MHz |
| 電壓/電流 - 輸出 1： | 1.2 V/1.8 V，700mA |
| 電壓/電流 - 輸出 2： | 1.2 V/1.8 V，300mA |
| 電壓/電流 - 輸出 3： | 1.2 V/1.8 V，300mA |
| 帶 LED 驅(qū)動(dòng)器： | 無 |
| 帶監(jiān)控器： | 無 |
| 帶序列發(fā)生器： | 無 |
| 電源電壓： | 2.7 V ~ 5.5 V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 16-WFBGA，CSPBGA |
| 供應(yīng)商設(shè)備封裝： | 16-UCSP（4x4） |
| 包裝： | 帶卷 (TR) |
700mA DC-DC Step-Down Converters
with Dual 300mA LDO in 2mm x 2mm CSP
10 ______________________________________________________________________________________
the off period, the low-side synchronous rectifier turns
on and remains on until the high-side switch turns on
again. The internal synchronous rectifier eliminates the
need for an external Schottky diode.
Hysteretic control is sometimes referred to as ripple con-
trol, since voltage ripple is used to control when the high-
side and low-side switches are turned on and off. To
ensure stability with low ESR ceramic output capacitors,
the MAX8884Y/MAX8884Z combine ripple from the out-
put with the ramp signal generated by the switching
node (LX). This is seen in Figure 2 with resistor R1 and
capacitor C1 providing the combined ripple signal.
Injecting ramp from the switch node also improves line
regulation, since the slope of the ramp adjusts with
changes in input voltage.
Hysteretic control has a significant advantage over fixed
frequency control schemes: fast transient response.
Hysteretic control uses an error comparator, instead of
an error amplifier with compensation, and there is no
fixed frequency clock. Therefore, a hysteretic converter
reacts virtually immediately to any load transient on the
output, without having to wait for a new clock pulse, or
for the output of the error amplifier to move, as with a
fixed-frequency converter.
With a fixed-frequency step-down converter, the magni-
tude of output voltage ripple is a function of the switching
frequency, inductor value, output capacitor and ESR,
and input and output voltage. Since the inductance value
and switching frequency are fixed, the output ripple
varies with changes in line voltage. With a hysteretic
step-down converter, since the ripple voltage is essen-
tially fixed, the switching frequency varies with changes
in line voltage. Some variation with load current is also
seen, however, this is part of what gives the hysteretic
converter its great transient response.
See the Typical Operating Characteristics section for
more information on how switching frequency can
change with load and line changes.
At inductor currents below 40mA (60mA), the MAX8884Y
(MAX8884Z) automatically switches to pulse-skipping
mode to improve light-load efficiency. Output voltage
ripple remains low at all loads, while the skip-mode
switching frequency remains ultrasonic down to 1mA
(typ) loads.
Voltage Positioning Load Regulation
The MAX8884Y/MAX8884Z step-down converters utilize
a unique feedback network. By taking a DC feedback
from the LX node through R1 in the Block Diagram, the
usual phase lag due to the output capacitor is
removed, making the loop exceedingly stable and
allowing the use of very small ceramic output capaci-
tors. To improve the load regulation, resistor R3 is
included in the feedback (see the Block Diagram). This
configuration yields load regulation equal to half the
inductors series resistance multiplied by the load cur-
rent. This voltage positioning load regulation greatly
reduces overshoot during load transients.
SEL Output Voltage Selection
SEL is used to determine the output voltage of the buck
converter and LDO1. See Table 1.
Shutdown Mode
Drive BUCK_EN to logic-low to place the MAX8884Y/
MAX8884Z step-down converter in shutdown mode. In
shutdown, the control circuitry, internal switching
MOSFET, and synchronous rectifier turn off and LX
becomes high impedance.
The LDOs are individually enabled. Connect LDO1_EN
and LDO2_EN to GND or logic-low to place LDO1 and
LDO2 in shutdown mode. In shutdown, the outputs of
the LDOs are pulled to ground through an internal
100&resistor.
When the step-down converter and all LDOs are in shut-
down, the MAX8884Y/MAX8884Z enter a very low-power
state, where the input current drops to 0.1礎(chǔ) (typ).
Step-Down Converter Soft-Start
The MAX8884Y/MAX8884Z step-down converter uses
internal soft-start circuitry to limit inrush current at startup,
reducing transients on the input source. Soft-start is partic-
ularly useful for supplies with high output impedance such
as Li+ and alkaline cells. See the soft-start waveforms in
the Typical Operating Characteristics.
V
V
I R
I loadcu
BUCK BUCK NO LOAD
LOAD DCR
LOAD
=
?/DIV>
=
_ _
2
rrrent
R DCimpedanceofinductor
V
DCR
BUCK NO LO
=
_ _ AAD
Vor VdependingonSEL
=12 18
. .
SEL
BUCK CONVERTER
OUTPUT VOLTAGE
(V)
LDO1
OUTPUT VOLTAGE
(V)
AGND
1.2
1.8
IN1_
1.8
2.8
Table 1. SEL Output Voltage Selection
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8884ZEREKE+T | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 700mA Step-Down DC/DC Converters RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX8885EUK25 | 制造商:Maxim Integrated Products 功能描述:LOW-DROPOUT LINEAR REGULATORS WITH - Rail/Tube |
| MAX8885EUK25+ | 制造商:Maxim Integrated Products 功能描述: |
| MAX8885EUK25+T | 功能描述:低壓差穩(wěn)壓器 - LDO 150mA Linear Regulator RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| MAX8885EUK25-T | 功能描述:低壓差穩(wěn)壓器 - LDO 150mA Linear Regulator RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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