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參數(shù)資料
| 型號： | MAX8512 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Ultra-Low-Noise.High PSRR.Low-Dropout.120mA Linear Regulators in SC70 |
| 中文描述： | 超低噪聲、高PSRR、低壓差、120mA線性穩(wěn)壓器 |
| 文件頁數(shù)： | 10/14頁 |
| 文件大?。?/td> | 296K |
| 代理商： | MAX8512 |
M
PWM Buc k Converters with Bypass FET
for N-CDMA/W-CDMA Handsets
10
______________________________________________________________________________________
High-Power Bypass Mode (MAX 8504)
A high-power bypass mode is available on the
MAX8504 for use when a PA transmits at high power.
This mode connects OUT to BATT through the bypass
PFET. Additionally, the PWM buck converter is forced
into 100% duty cycle to further reduce dropout.
S hutdown Mode
Driving
SHDN
to GND places the MAX8500
–
MAX8504 in
shutdown mode. In shutdown, the reference, control cir-
cuitry, internal switching MOSFET, and synchronous rec-
tifier turn off and the output becomes high impedance.
Input current falls to 0.1μA (typ) during shutdown mode.
Drive
SHDN
high for normal operation.
Current-S ense Comparators
The MAX8500
–
MAX8504 use several internal current-
sense comparators. In PWM operation, the PWM com-
parator terminates the cycle-by-cycle on-time and
provides improved load and line response. A second
current-sense comparator used across the P-channel
switch controls entry into skip mode. A third current-
sense comparator monitors current through the internal
N-channel MOSFET to prevent excessive reverse cur-
rents and determine when to turn off the synchronous
rectifier. A fourth comparator used at the P-channel
MOSFET detects overcurrent. A fifth comparator used
at the bypass/LDO P-channel MOSFET detects over-
current in the HP mode or at dropout. This protects the
system, external components, and internal MOSFETs
under overload conditions.
Applic ations Information
S etting the Output V oltage
Using a DAC (MAX8500–MAX8503)
The MAX8500
–
MAX8503 are optimized for highest sys-
tem efficiency when applying power to a linear PA in
CDMA handsets. When transmitting at less than full
power, the supply voltage to the PA is lowered from
V
BATT
to as low as 0.4V to greatly reduce battery cur-
rent. Figure 3 shows the typical CDMA PA load profile.
The use of DC-to-DC converters such as the MAX8500
–
MAX8503 dramatically extends talk time in these appli-
cations.
The MAX8500
–
MAX8503s
’
output voltage is dynamically
adjustable from 0.4V to V
BATT
by the use of the REFIN
input. The gain from V
REFIN
to V
OUT
is internally set to
1.76X (MAX8500 and MAX8502) or 2X (MAX8501 and
MAX8503). V
OUT
can be adjusted during operation by
driving REFIN with an external DAC. The MAX8500
–
MAX8503 output responds to full-scale change in voltage
and current in <30μs.
Using External Divider (MAX8504)
The MAX8504 is intended for two-step V
CC
control
applications where high efficiency is a priority. Select
an output voltage between 1.25V and V
BATT
by con-
necting FB to a resistive divider between the output
and GND (Figure 4). Select feedback resistor R2 in the
5k
to 50k
range. R1 is then given by:
where V
FB
= 1.25V.
R
-1
1
2
=
×
R
V
V
OUT
FB
30
0
600
W-CDMA PA SUPPLY CURRENT (mA)
300
0.4
0
1.0
3.0
3.4
W
Figure 3. Typical W-CDMA Power Amplifier Load Profile
R1
R2
50k
MAX8504
LX
FB
Figure 4. Setting the Adjustable Output Voltage
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX8515EVKIT | Evaluation Kit for the MAX8515/MAX8515A |
| MAX8523 | High-Speed. Dual-Phase Gate Driver for Multiphase. Step-Down Converters |
| MAX8529 | 1.5MHz Dual 180°. Out-of-Phase PWM Step-Down Controller with POR |
| MAX8529EVKIT | Evaluation Kit for the MAX8529 |
| MAX8555AEVKIT | Evaluation Kit for the MAX8555A |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8512ETA+T | 功能描述:低壓差穩(wěn)壓器 - LDO 120mA 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(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 |
| MAX8512EXK | 制造商:Maxim Integrated Products 功能描述:ULTRA-LOW NOISE, HIGH PSRR, LOW-DROPOUT, 120M - Cut Tape Product |
| MAX8512EXK+ | 制造商:Maxim Integrated Products 功能描述:REG LDO LIN ADJ POS 1.5V TO 4.5V 0.12A 5PIN SC-70 - Bulk |
| MAX8512EXK+T | 功能描述:低壓差穩(wěn)壓器 - LDO 120mA 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(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 |
| MAX8512EXK-T | 功能描述:低壓差穩(wěn)壓器 - LDO 120mA 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(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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