LT1187CS8 Linear Technology, LT1187CS8 Datasheet - Page 10

• Manufacturer Part Number: LT1187CS8
• Description: IC AMP VIDEO DIFFRNC ADJ 8-SOIC
• Manufacturer: Linear Technology

Specifications of LT1187CS8

• Applications: Differential
• Number Of Circuits: 1
• -3db Bandwidth: 50MHz
• Slew Rate: 165 V/µs
• Current - Supply: 13mA
• Current - Output / Channel: 20mA
• Voltage - Supply, Single/dual (±): 4.75 V ~ 16 V, ±2.38 V ~ 8 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS INFORMATION
LT1187
Using the Shutdown Feature
The LT1187 has a unique feature that allows the amplifi er
to be shutdown for conserving power, or for multiplexing
several amplifi ers onto a common cable. The amplifi er
will shut down by taking Pin 5 to V
amplifi er dissipates 15mW while maintaining a true high
impedance output state of 20k in parallel with the feedback
resistors. For MUX applications, the amplifi ers may be
confi gured inverting, noninverting or differential. When
the output is loaded with as little 1k from the amplifi er’s
feedback resistors, the amplifi er 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
10
(A) STANDARD INPUTS, PINS 2 TO 3, V
(B) EXTENDED INPUTS, PINS 2 TO 2, V
(C) EXTENDED INPUTS, PINS 1 TO 2, V
A
1MHz Sine Wave Gated Off with Shutdown Pin
V
= 2, R
FB
= R
G
= 1k
LT1187 in Unity Gain
IN
IN
IN
= 1.0V
= 2.0V
= 1.0V
P-P
P-P
P-P
–
. In shutdown, the
LT1187 • AI06
LT1187 • AI07
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.
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 amplifi er.
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 amplifi er’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 R
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 760mV
1.5MHz Square Wave Input and Unequalized Response
Through 1000 Feet of Twisted-Pair
P-P
.
G
. At Transmit 2, another
LT1187 • AI08
1187fa