參數(shù)資料
型號: SC250WLTRT
廠商: Semtech Corporation
元件分類: DC/DC變換器
英文描述: Step-Down DC-DC Converter with Bias LDO for RF Power Amplifi ers
中文描述: 降壓的DC - DC轉(zhuǎn)換器偏置穩(wěn)壓器射頻功率擴增再培訓(xùn)計劃
文件頁數(shù): 1/18頁
文件大?。?/td> 851K
代理商: SC250WLTRT
1
www.semtech.com
SC250
Step-Down DC-DC Converter with
Bias LDO for RF Power Ampli
fi
ers
POWER MANAGEMENT
Description
August 28, 2006
Typical Application Circuit
Applications
CDMA and WCDMA Phones
Handheld Radios
RF PC Cards
Battery Powered RF Devices
The SC250 is a synchronous step-down converter
designed speci
fi
cally for use as an adaptive voltage
supply for CDMA and WCDMA RF Power Ampli
fi
ers (PAs).
The output voltage can be adjusted dynamically between
0.3V and (Vin - 0.4)V through a linear analog control input.
For high power operation, a maximum control input signal
level forces the device into bypass mode where the input
is connected directly to the output via an internal P-
Channel pass transistor. Bypass mode also occurs when
the output load demands duty cycles in excess of the
maximum rated duty cycle.
The SC250 also provides an LDO regulator which can be
used to supply a 2.85V bias to the PA. The internal clock
runs at 1MHz to maximize ef
fi
ciency while still allowing
the use of small surface mount inductors and capacitors
can be used.
The peak current rating of the internal PMOS switch allows
a DC output current of 600mA. The bypass PMOS current
rating allows a minimum of 1A DC output current in the
bypass mode. Shutdown turns off all the control circuitry
to achieve a typical shutdown current of 0.1
μ
A.
Adjustable output voltage range — 0.3 to 3.6V
Linearly proportional V
DAC
to V
OUT
relationship for
increased PA ef
fi
ciency
Pass-through mode automatic and on demand
Input voltage range — 2.7V to 5V
Typical settling time — 40
μ
s
Output current capability — 600mA
Maximum output current in bypass mode — 1A
Up to 96% ef
fi
ciency
Constant frequency operation — 1MHz
Less than 1
μ
A shutdown current
Internal 75m
Ω
PMOS bypass transistor
PA bias voltage supply — 2.85V, 20mA, 1.5%
MLPD-W8, 2.3 x 2.3mm package
L1
4.7
μ
H
C
IN
10
μ
F
VIN
VOUT
VREF
GND
LX
VDAC
PGND
C
REF
1
μ
F
EN
C
OUT
4.7
μ
F
V
IN
3
6
1
4
2
7
5
8
PA
RF Output
RF Input
Vcc
GND
BIAS
ENABLE
VDAC
SC250
Features
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