LT1187M 查看數據表（PDF） - Linear Technology

零件编号

产品描述 (功能)

生产厂家

LT1187M

Low Power Video Difference Amplifi er

Linear Technology 

LT1187

APPLICATIONS INFORMATION

LT1187 in Unity Gain

Performance Characteristics section. At very high elevated

temperature it is important to hold the shutdown pin close

to the negative supply to keep the supply current from

increasing.

(A) STANDARD INPUTS, PINS 2 TO 3, VIN = 1.0VP-P

(B) EXTENDED INPUTS, PINS 2 TO 2, VIN = 1.0VP-P

(C) EXTENDED INPUTS, PINS 1 TO 2, VIN = 2.0VP-P

LT1187 • AI06

Using the Shutdown Feature

The LT1187 has a unique feature that allows the amplifier

to be shutdown for conserving power, or for multiplexing

several amplifiers onto a common cable. The amplifier

will shut down by taking Pin 5 to V–. In shutdown, the

amplifier dissipates 15mW while maintaining a true high

impedance output state of 20k in parallel with the feedback

resistors. For MUX applications, the amplifiers may be

configured inverting, noninverting or differential. When

the output is loaded with as little 1k from the amplifier’s

feedback resistors, the amplifier shuts off in 600ns. This

shutoff can be under the control of HC CMOS operating

between 0V and –5V.

The ability to maintain shutoff is shown on the curve

Shutdown Supply Current vs Temperature in the Typical

1MHz Sine Wave Gated Off with Shutdown Pin

Send Color Video Over Twisted-Pair

With an LT1187 it is possible to send and receive color

composite video signals more than 1000 feet on a low cost

twisted-pair. A bi-directional “video bus” consists of the

LT1195 op amp and the LT1187 video difference amplifier.

A pair of LT1195s at Transmit 1 is used to generate dif-

ferential signals to drive the line which is back-terminated

in its characteristic impedance. The LT1187 twisted-pair

receiver converts signals from differential to single-ended.

Topology of the LT1187 provides for cable compensation

at the amplifier’s feedback node as shown. In this case,

1000 feet of twisted-pair is compensated with 1000pF

and 50Ω to boost the 3dB bandwidth of the system from

750kHz to 4MHz. This bandwidth is adequate to pass a

3.58MHz chroma subcarrier and the 4.5MHz sound sub-

carrier. Attenuation in the cable can be compensated by

lowering the gain set resistor RG. At Transmit 2, another

pair of LT1195s serve the dual function to provide cable

termination via low output impedance, and generate dif-

ferential signals for Transmit 2. Cable termination is made

up of a 15Ω and 33Ω attenuator to reduce the differential

input signal to the LT1187. Maximum input signal for the

LT1187 is 760mVP-P.

1.5MHz Square Wave Input and Unequalized Response

Through 1000 Feet of Twisted-Pair

AV = 2, RFB = RG = 1k

10

LT1187 • AI07

LT1187 • AI08

1187fa

Share Link: