ML6680
PIN DESCRIPTION
PIN# NAME
FUNCTION
PIN# NAME
FUNCTION
1, 28 XTAL1,
XTAL2
Crystal inputs. A 32.768kHz watch
crystal connected between these pins
provides timing for the fiber optic
insertion key signal. An external clock
can be used to drive XTAL1 while
grounding XTAL2. The frequency of
the external clock should be between
32.7kHz and 34.5kHz.
Positive 5V power supply.
13
RTSETTP
Twisted pair transmit level set resistor
input. A precision resistor between
RTSETTP and VCC sets the amplitude
of the TPOUTP/N output.
Positive 5V power supply.
14
15
VCC1
2
3, 4
V
CC2
EQA, EQB Equalizer network pins. An external
combination of two resistors and a
capacitor connected at EQA and EQB
sets up the on-chip twisted pair
receive equalizer.
Receive twisted pair inputs. This
differential input pair receives
differential Manchester signals from
the coupling transformer (or PECL
compatible levels).
Phantom drive/sense inputs/outputs. In
configuration 1, these pins are TTL
inputs from two external opto
isolators. They are low when phantom
power is present and high when
phantom power is removed. These
pins provide the phantom drive
current and are used to check for a
wire fault on the phantom circuits
when it is required in configuration 2.
In configuration 3, these pins are don’t
cares. In configuration 4, these pins
are low for normal operation, or any
or both of them is high to force the
ML6680 into the “Bypass State.”
Ground.
5, 6 TPINP/N
INSERTED
Insertion indicator. It is an active low,
open collector LED driver. In
configurations 1, 3 and 4 this output
goes low when the ML6680 is in the
“Insert State.” In configuration 2 this
output goes low when the ML6680 is
in the “Insert State” and no wire fault
is detected. This input is tied to ground
to disable the frequency squelch, and
to reduce the time constant of the
amplitude squelch of the optical input.
RTSETOP
A precision resistor between RTSETOP
and VCC sets the amplitude of the
OPOUT output.
Valid fiber optic input signal indicator.
It is an active low, open collector LED
driver. This output goes low when the
signal at OPINP/N meets frequency
and amplitude squelch limit for
received signals at TPINP/N.
Positive 5V power supply for fiber
optic LED driver.
Fiber optic LED driver output. The
fiber optic LED connects between this
pin and OPVCC.
Ground for the fiber optic LED driver.
Ground.
Key generation select CMOS input.
This input is low for configurations 2
and 3 of the general description, and is
high for configurations 1 and 4.
Offset correction time constant
capacitor input. An external capacitor
between this pin and QGND
determines the time constant of the
internal offset correction circuit for the
fiber optic quantizer.
Quantizer’s ground.
Receive fiber inputs. This pair of inputs
receive differential Manchester signals
from the fiber optic receiver/preamp
and present them to the on-chip fiber
optic quantizer. These inputs should
be capacitively coupled to the input
source. The input resistance is
approximately 1.3kΩ.
Quantizer’s positive 5V power supply.
16
7, 8 PHTM1/2
17
OPINOK
18
19
OPVCC
OPOUT
20
21
22
OPGND
GND1
KEYGEN
9
GND2
10, 11 TPOUTP/N Transmit twisted pair outputs. This
differential current output pair drives
differential Manchester signals into the
network coupling transformer and
transmit filter. Output edge rates are
controlled to allow use of a simpler
filter than would otherwise be
required. These outputs can be PECL
compatible with an external resistor
network.
12
TPINOK
Valid twisted pair input signal
indicator. It is an active low, open
collector LED driver. This output goes
low when the signal at TPINP/N meets
frequency and amplitude squelch
requirements. This input is tied to
ground for configurations 3 and 4 to
enable signal path switching.
23
VDC
24
QGND
26, 25 OPINP/N
27
QVCC
3
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
