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MPC100

APPLICATIONS INFORMATION

The MPC100 operates from

±5V power supplies (±6V

maximum). Do not attempt to operate with larger power

supply voltages or permanent damage may occur. The buffer

outputs are not current-limited or protected. If the output is

shorted to ground, currents up to 18mA could flow. Momen-

tary shorts to ground (a few seconds) should be avoided, but

are unlikely to cause permanent damage.

INPUT PROTECTION

All pins on the MPC100 are internally protected from ESD

by means of a pair of back-to-back reverse-biased diodes to

either power supply as shown in Figure 1. These diodes will

begin to conduct when the input voltage exceeds either

power supply by about 0.7V. This situation can occur with

loss of the amplifier’s power supplies while a signal source

is still present. The diodes can typically withstand a continu-

ous current of 30mA without destruction. To insure long

term reliability, however, diode current should be externally

limited to 10mA or less whenever possible.

The internal protection diodes are designed to withstand

2.5kV (using Human Body Model) and will provide ad-

equate ESD protection for most normal handling proce-

dures. However, static damage can cause subtle changes in

amplifier input characteristics without necessarily destroy-

ing the device. In precision buffer amplifiers, this may cause

a noticeable degradation of offset voltage and drift. There-

fore, static protection is strongly recommended when han-

dling the MPC100.

Static damage has been well recognized for MOSFET de-

vices, but any semiconductor device deserves protection

from this potentially damaging source. The MPC100 incor-

porates on-chip ESD protection diodes as shown in Figure 1.

This eliminates the need for the user to add external protec-

tion diodes, performance.

DISCUSSION

OF PERFORMANCE

The MPC100 video multiplexer allows the user to connect

of the component and to switch between channels within

less than 0.5

µs. It consists of four identical unity-gain buffer

amplifiers, which are connected together internally at the

output. The open loop buffers consisting of complementary

–V

CC

+V

CC

ESD Protection diodes

internally connected to all pins.

Internal Circuitry

External Pin

FIGURE 1. Internal ESD Protection.

emitter followers applies no feedback, so their low fre-

quency gain is slightly less than unity and somewhat depen-

dent on loading. Unlike devices using MOS bilateral switch-

ing elements, the bipolar complementary buffers form an

unidirectional transmission path and thus provide high out-

put-to-input isolation. Switching stages compatible to TTL

level digital signals are provided for each buffer to select the

input channel. When no channel is selected, the output of the

device is high-impedance and allows the user to wire more

MPC100s together to form switch multi-channel matrices.

If one channel is selected with a digital “1” at the corre-

sponding SEL-input, the MPC100 acts as a buffer amplifier

with high input impedance and low output impedance. The

truth table on the front page describes the relationship

output.

The 2-4 address decoder and chip select logic is not

integrated. The selected design increases the flexibility of

address decoding in complex distribution fields, eases

BUS-controlled channel selection, simplifies channel se-

lection monitoring for the user, and lowers transient peaks.

All of these characteristics make the multiplexer, in effect,

a quad switchable high-speed buffer. It requires DC cou-

pling and termination resistors when directly driven from

a low impedance cable. High-current output amplifiers are

recommended when driving low-impedance transmission

lines or inputs.

An advanced complementary bipolar process, consisting of

pn-junction isolated high-frequency NPN and PNP transis-

tors, provides wide bandwidth while maintaining low

crosstalk and harmonic distortion. The single chip band-

width of over 250MHz at an output voltage of 1.4Vp-p

allows the design of large crosspoint or distribution fields

in HDTV-quality with an overall system bandwidth of

36MHz. The buffer amplifiers also offer low differential

gain (0.05%) and phase (0.01

°) errors. These parameters

are essential for video applications and demonstrate how

well the signal path maintains a constant small-signal gain

and phase for the low-level color subcarrier at 4.43MHz

(PAL) or 3.58MHz (NSTC) as the brightness (luminance)

signal is ramped through its specified range. The bipolar

construction also ensures that the input impedance remains

high and constant between ON and OFF states. The ON/

OFF input capacitance ratio is near unity, and does not vary

with power supply voltage variations. The low output

capacitance of 1.5pF when no channel is selected is a very

important parameter for large distribution fields. Each par-

allel output capacitance is an additional load and reduces

the overall system bandwidth.

Bipolar video crosspoint switches are virtually glitch-free

when compared to signal switches using CMOS or DMOS

devices. The MPC100 operates with a fast make-before-

break switching action to keep the output switching tran-

sients small and short. Switching from one channel to

another causes the signal to mix at the output for a short

time, but it interferes only minimally with the input signals.