參數(shù)資料
型號: MAX8533
廠商: Maxim Integrated Products, Inc.
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: Smallest. Most Reliable. 12V. Infiniband-Compliant Hot-Swap Controller
中文描述: 更小、更可靠的12V、InfiniBand兼容熱插拔控制器
文件頁數(shù): 10/14頁
文件大?。?/td> 296K
代理商: MAX8533
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
MAX8533EVKIT Evaluation Kit for the MAX8533
MAX8535EVKIT Evaluation Kit for the MAX8535
MAX8536 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies
MAX8536EVKIT Evaluation Kit for the MAX8536
MAX853CSA DC-to-DC Voltage Converter
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參數(shù)描述
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