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參數(shù)資料
| 型號(hào)： | MAX2745 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Single-Chip Global Positioning System Receiver Front-End |
| 中文描述： | 單芯片、全球定位系統(tǒng)前端下變頻器 |
| 文件頁數(shù)： | 7/9頁 |
| 文件大?。?/td> | 410K |
| 代理商： | MAX2745 |
M
Single-Chip Global Positioning System
Receiver Front-End
_______________________________________________________________________________________
7
Temperature Sensor
The MAX2745 features an on-chip temperature sensor to
facilitate system temperature compensations in conjunc-
tion with the trimmed capacitor. This circuit generates an
output voltage at TEMPOUT, which is used to approxi-
mate the temperature by the following equation:
T = T
O
+ (V
OUT
- V
OUT,TO
)/SG
where SG is the sensor gain, T
O
is factory-trimmed tem-
perature, which can be any value (normally +27
°
C), and
V
OUT
is the temperature output voltage at T
O
. The coeffi-
cient SG in the above equation is targeted to be between
6mV/
°
C and 8mV/
°
C, depending on the temperature.
Voltage Booster
The MAX2745 integrates an internal voltage booster to
allow proper operation with supply voltages as low as
1.6V. The circuit includes two 6nF floating external
capacitors connected to VB_CS
±
(pins 22 and 23) and
a 1μF capacitance to V
OUT
(boosted voltage output,
pin 24). To reduce the output voltage ripple, use an
external LC lowpass filter, which can be built with two
inductors and one capacitor.
Applications Information
Operation with Voltage Booster
Under normal operating conditions, the recommended
power-supply voltage ranges from 2.4V to 3.6V. But
with the integrated voltage booster on-chip, the
MAX2745 can be powered from power-supply voltages
as low as 1.6V, and only requires a minimal number of
external components. This is not the most efficient
operating mode, since the power efficiency will be low-
ered to less than 50%.
As described in the
Detailed Description
section, to use
the voltage booster, connect 6nF floating capacitors to
VB_CS
±
, pins 22 and 23, and 1μF bypass capacitor to
V
OUT
, pin 24. Connect V
OUT
(pin 24) to all the power-
supply (V
DD
) pins and pull BST_CTRL, pin 17, high to
activate the booster. Then the MAX2745 can be pow-
ered from supply voltages ranging from 1.6V to 2.3V at
VDD_VB, pin 19, and the voltage booster output can
source up to 25mA current. It is recommended that the
voltage booster be used as a backup supply. To do
this, additional circuits including a voltage monitor and
a switch are needed. These components are inexpen-
sive and can be found in the Maxim product family.
Layout Issues
A properly designed PC board is an essential part of
any RF/microwave circuit. Use the MAX2745 EV kit as a
guide. Use controlled-impedance lines on all frequency
inputs and outputs. Use low inductance connections to
ground on all ground pins and wherever the compo-
nents are connected to ground. Place decoupling
capacitors close to all V
CC
connections. For proper
operation, connect the metal exposed paddle at the
back of the IC to the PC board ground plane with multi-
ple vias.
Chip Information
TRANSISTOR COUNT: 9205
PROCESS: CMOS
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| MAX2745ECM+T | 制造商:Maxim Integrated Products 功能描述:RCVR FRONT-END 48TQFP EP - Tape and Reel |
| MAX2745ECM+TD | 功能描述:上下轉(zhuǎn)換器 GPS Front End Downconverter RoHS:否 制造商:Texas Instruments 產(chǎn)品:Down Converters 射頻:52 MHz to 78 MHz 中頻:300 MHz LO頻率: 功率增益: P1dB: 工作電源電壓:1.8 V, 3.3 V 工作電源電流:120 mA 最大功率耗散:1 W 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFP-128 |
| MAX2745EVKIT | 功能描述:射頻開發(fā)工具 RoHS:否 制造商:Taiyo Yuden 產(chǎn)品:Wireless Modules 類型:Wireless Audio 工具用于評(píng)估:WYSAAVDX7 頻率: 工作電源電壓:3.4 V to 5.5 V |
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