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參數(shù)資料
| 型號： | MAX8868EUKxy-T |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Low-Noise, Low-Dropout, 150mA Linear Regulators in SOT23 |
| 中文描述： | 低噪聲，低壓差，150mA的線性穩(wěn)壓器采用SOT23 |
| 文件頁數(shù)： | 13/20頁 |
| 文件大?。?/td> | 257K |
| 代理商： | MAX8868EUKXY-T |
M
Wireless and S atellite Handset
Power-Management ICs
______________________________________________________________________________________
13
The serial interface programs V
OUT0
from 2.625V to
3.75V in 75mV steps for the MAX886 (Tables 1 and 2),
or from 1.527V to 3.027V in 100mV steps for the
MAX888 (Tables 1 and 3).
Regulator 0 operates in one of four preset frequencies,
from 375kHz to 925kHz, programmable through the
serial interface (Table 4).
For the device to power up properly, V
IN0
must be high
enough for REG0 to get into regulation. For the MAX886,
Regulator 0’s default voltage is 3.75V. Since the rest of
the regulators do not power up until Regulator 0 is
ready, V
IN0
must be greater than approximately 4V for
the device to power up properly. The Regulator 0 default
voltage for the MAX888 is 2.027V, so the minimum V
IN0
required to start up is limited by the minimum operating
voltage range (2.7V). After power-up, the device oper-
ates until V
BATT
drops below V
UVLOF
(undervoltage
lockout falling threshold).
Sync Mode
The SYNC input allows the MAX886/MAX888 to syn-
chronize with an external clock applied to SYNC, ensur-
ing that switching harmonics are kept away from
sensitive IF bands. The SYNC detector triggers on
SYNC’s falling edge.
PWM Mode
Regulator 0 is in PWM mode when SYNC is connected to
CVL or driven to a logic-high voltage. Two internal switch-
es operate at a preset frequency even when there is no
load. The P-channel MOSFET turns on to charge the
inductor until the error comparator or current-limit com-
parator turns it off. The N-channel MOSFET then turns on
to discharge the inductor. To prevent the output from
soaring with no load in PWM mode, the N-channel switch
stays on long enough to allow the inductor current to go
negative. Once the N-channel switch turns off, the voltage
at LX rises (rings) until the next cycle when the P-channel
switch turns on again. As the load increases and the
inductor enters continuous conduction, ringing is no
longer present and the LX waveform looks like a square
wave whose duty cycle depends on the input and output
voltages. As the input voltage approaches the same level
as the output voltage, the P-channel switch stays on
100% of the time, providing the lowest possible dropout.
PFM Mode
Regulator 0 operates in PFM mode when SYNC is dri-
ven to a logic low voltage or connected to GND. When
V
OUT0
drops below the regulation threshold, the P-
channel switch turns on to charge the inductor until the
error comparator or current-limit comparator turns it off.
At light loads, the N-channel then turns on to discharge
the inductor until the current in the inductor reaches
zero. In PFM mode, the inductor current does not go
negative to discharge the output. At no-load there is a
long period between pulses of inductor current. As the
load current increases, the period between pulses
becomes shorter until the pulses become continuous. At
load currents above this point, Regulator 0 automatically
switches to PWM mode, and the V
LX
waveform looks like
a square wave whose duty cycle depends on the input
and output voltages. As the input voltage approaches
the same level as the output voltage, the P-channel
switch stays on 100% of the time, providing the lowest
possible dropout. It is typically more efficient to use the
PFM mode when the load current is less than 100mA.
100mA LDO Regulator 1
Regulator 1, a low-dropout linear regulator, sources a
minimum of 100mA and operates from voltages at IN1
of up to 12V. The serial interface programs V
OUT1
from
2.7V to 4.95V in 75mV steps for the MAX886 (Tables 1
and 2), or from 1.25V to 3.50V in 150mV steps for the
MAX888 (Tables 1 and 3). IN1 may be powered from
the battery, OUT0, or any other voltage source.
200mA LDO Regulator 2
Regulator 2, a low-dropout linear regulator, sources a
minimum of 200mA. The serial interface programs V
OUT2
from 2.175V to 3.3V in 75mV steps for the MAX886 (Tables
1 and 2), or from 1.527V to 3.027V in 100mV steps for the
MAX888 (Tables 1 and 3). IN2 may be powered from the
battery, OUT0, or any other voltage source less than 5.5V.
20mA LDO Regulator 3
Regulator 3, a low-dropout linear regulator, sources a
minimum of 20mA. The serial interface programs V
OUT3
to one of four different output voltages: 0V, 2.85V, 4.65V,
or V
OUT2
(Tables 1 and 5). Although this is a general-
purpose output, OUT3 is intended for the SIM supply. IN3
may be powered from OUT4 or from any regulated 5V
supply.
When programmed to 0V or V
OUT2
, OUT3 is either actively
discharged to GND (for 0V mode) or connected to OUT2
(for V
OUT2
), and Regulator 3 is disabled to conserve
power.
100mA Charge-Pump Regulator 4
Regulator 4, a regulated charge pump, generates 5.25V
and delivers up to 100mA. An oscillator synchronized to the
PWM clock regulates OUT4 to minimize noise. It operates
at one-half the frequency of the PWM oscillator to ensure
50% duty-cycle outputs. IN4 may be powered from the bat-
tery, OUT0, or any other voltage source less than 5.5V.
To save space and cost, use a small ceramic flying
capacitor. See Table 6 for recommended flying capaci-
tor values.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8868EZK25 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX8868EZK25-T | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX8868EZK28+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 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| MAX8868EZK29+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 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| MAX8869EUA25 | 制造商:Maxim Integrated Products 功能描述: |
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