MAX4158ESA Просмотр технического описания (PDF) - Maxim Integrated
Номер в каталоге
Компоненты Описание
Список матч
MAX4158ESA Datasheet PDF : 16 Pages
| |||
350MHz/250MHz, 2-Channel
Video Multiplexer-Amplifiers
_______________Detailed Description
The MAX4158/MAX4159 are optimized for closed-loop
gains (AVCL) of 1V/V (0dB) or greater; the MAX4258/
MAX4259 are optimized for closed-loop gains of 2V/V
(6dB) or greater. These low-power, high-speed, cur-
rent-mode feedback amplifiers operate from ±5V sup-
plies. They drive video loads (including 50Ω and 75Ω
cables) with excellent distortion characteristics.
Differential gain and phase errors are 0.01%/0.01° for
MAX4158/MAX4159 and 0.01%/0.02° for MAX4258/
MAX4259, respectively.
The input multiplexers feature very short switching
times and small switching transients. They also have
high input resistance and constant input capacitance,
so overall input impedance can be set by external input
terminating resistors. Each video input is isolated by an
AC-ground pin, which reduces channel-to-channel
capacitance and minimizes crosstalk.
The MAX4159/MAX4259 have address latching and an
output enable function that places the output in a high-
impedance state. These functions allow multiple
mux/amps to be paralleled together to form larger
switching arrays.
________________________Truth Tables
Input Control Logic
LOGIC
INPUTS
LE A0
AMPLIFIER
INPUT
FUNCTION
0
0
0
1
1
X
X = Don’t Care
IN0
IN1
[LAST]
Channel 0 selected
Channel 1 selected
Channel addresses latched;
retains last input address.
MAX4159/MAX4259
Output Control Logic
LOGIC
INPUT
( EN )
AMPLIFIER
OUTPUT
FUNCTION
0
On
Output on
1
Off
Output off; high impedance
All logic levels (EN, LE, and A0) default low (0) if left open circuit.
Output disable is completely independent of input address and
latch.
__________Applications Information
Theory of Operation
Since the MAX4158/MAX4159/MAX4258/MAX4259 are
current-mode feedback amplifiers, their open-loop
transfer function is expressed as a transimpedance,
∆VOUT/∆IFB, or ZT. The frequency behavior of this
open-loop transimpedance is similar to the open-loop
gain of a voltage-mode feedback amplifier. That is, it
has a large DC value and decreases at approximately
6dB per octave at high frequency.
Analyzing the current-mode feedback amplifier in a
gain configuration (Figure 1) yields the following trans-
fer function:
VOUT / VIN = G x ZT(S) / (ZT(S) + G x RIN(FB) + RF)
where G = AVCL = 1 + RF / RG.
At low gains, G x RIN(FB) << RF. Therefore, unlike tradi-
tional voltage-mode feedback amplifiers, the closed-
loop bandwidth is essentially independent of
closed-loop gain. Note also that at low frequencies,
ZT >> [G x RIN(FB) + RF] so:
VOUT / VIN = G = 1 + RF / RG
Layout and Power-Supply Bypassing
The MAX4158/MAX4159/MAX4258/MAX4259 have
extremely high bandwidth, and consequently require
careful board layout, including the possible use of con-
stant-impedance microstrip or stripline techniques.
RG
FB
IN0
VIN
IN1
RF
RIN(FB)
ZT
OUT
+1
+1
MAX4158
MAX4159
MAX4258
MAX4259
Figure 1. Current-Mode Feedback Amplifier
10 ______________________________________________________________________________________
Share Link: 