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XR-2277 Datasheet Preview

XR-2277 Datasheet

Dot and Bar Graph Display Generators

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XR·2277/2278
Dot and Bar Graph Display Generators
GENERAL DESCRIPTION
FUNCTIONAL BLOCK DIAGRAM
The XR-2277 and XR-2278 are 12 point level detector
circuits designed for direct interfacing to light emitting
diode (LED) moving-dot or bar-graph displays. Each of
the circuits is comprised of an input buffer amplifier
and 12 comparators, biased from a resistor string at
logarithmic intervals. Accuracy is enhanced by an in-
ternal reference. Each comparator provides a high im-
pedance current source output which are all very
closely matched and simultaneously adjustable with a
single external resistor. A control signal applied to the
mode select pin determines whether the display is driv-
en in a moving-dot or bar-graph format.
FEATURES
High Impedance Buffered Input
Direct LED Interface
Constant Current Outputs
External Dot/Bar Mode Select
ORDERING INFORMATION
Part Number
XR-2277P
XR-2278P
Package
Plastic
Plastic
Operating Temperature
o·e to + 70·e
o·e to + 70·e
APPLICATIONS
Bar-Graph Display Generator/Driver
Moving-dot Display Driver
Sequential Display Indicator
Audio Level Indicator
ABSOLUTE MAXIMUM RATINGS
Power Supply
Power Dissipation
Derate Above 25·e
Operating Temperature Range
Storage Temperature Range
15V
625 mW
5 mW/·e
o·e to + 70·e
-65·e to + 150·e
SYSTEM DESCRIPTION
The XR-2277 and XR-2278 are 12 point logarithmic lev-
el detectors and LED drivers. LED driving current is
provided by on board adjustable current sinks; no se-
ries limiting resistors are required. All LEOs receive
matched currents, ensuring equal brightness. The driv-
ers can be programmed to source up to 22 mA.
The LED current is set by a resistor from Pin 2 to
Ground. The zero dB reference is set by varying the bi-
as on Pin 3. The output may be either moving dot (one
segment only) or bar mode (all segments up to the mea-
sured value illuminated). This is determined by Pin 18.
The XR-2277 provides 12 discrete outputs for an input
level range of - 30 dB to + 6 dB, referenced to an inter-
nally set zero dB level which is typically 0.2 VRMS. The
XR-2278 has similar electrical charcteristics, providing
a - 20 dB to + 8 dB input dynamic range referenced to
0.13 VRMS. Both parts operate from a nominal 12V
supply.
1-246




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XR-2277 Datasheet Preview

XR-2277 Datasheet

Dot and Bar Graph Display Generators

No Preview Available !

XR·2277/2278
ELECTRICAL CHARACTERISTICS vcc = 12 Volts, TA = 25°C, unless otherwise specified. (See Test Circuit of Figure 2.)
XR-2277
XR-2278
PARAMETERS
MIN TYP MAX MIN TYP MAX UNITS CONDITIONS
Supply Voltage
Supply Current
10 12 14 10 12 14 VDC VF(LED) = 2 V
5 10
5 10 mA VIN = 0 V
LED Current
22 22 mA R2 Varied
See Figure 4
LED Current
12 15 18 12 15 18 mA R2 = 27 KIl
ILED Matching between Outputs -1.5
+1.5 -1.5
+1.5 mA R2 = 27 KIl
Input Voltage for 0 dB Output
0.10 0.20 0.25 0.09 0.13 0.18 VRMS o dB Output Threshold
Input Current
50 50 nA
Outputs
Output 1 (pin 17)
Output 2 (pin 16)
Output 3 (pin 15)
Output 4 (pin 14)
Output 5 (pin 13)
Output 6 (pin 12)
Output 7 (pin 11)
Output 8 (pin 10)
Output 9 (pin 8)
Output 10 (pin 7)
Output 11 (pin 6)
Output 12 (pin 5)
-31.5 -30.0 -28.5
20.0
dB See Note 1
-27.0
-16.5 -15.0 -13.5 dB See Note 2
-25.0 -24.0 -23.0 -11.5 -10.0 -8.5 dB
-21.5 -20.0 -18.5 -8.0 -7.0 -6.0 dB
-18.5 -17.0 -15.5 -6.0 -5.0 -4.0 dB
-15.5 -14.0 -12.5 -4.0 -3.0 -2.0 dB
-11.0 -10.0 -9.0 -1.5 -1.0 -0.5 dB
-8.0 -7.0 -6.0
0
dB
-5.0 -4.0 -3.0 +0.5 +1.0 +1.5 dB
0 +2.0 +3.0 +4.0 dB
+2.0 +3.0 +4.0 +4.0 +5.0 +6.0 dB
+4.5 +6.0 +7.5 +6.5 +8.0 +9.5 dB
NOTES:
1. Calibration adjustment for XR-2277: An input voltage, VIN, is applied at -27 dB level, referenced to zero dB
setting, and R1 is adjusted until Output 2 (Pin 16) turns on.
2. Calibration adjustment for XR-2278: An input voltage, VIN, is applied at -20 dB level, referenced to zero dB
setting, and Rl is adjusted until Output 1 (Pin 17) turns on.
Vcc
RL -------------- RL
OUTPUT 0 - - ~ ILED
I
~~ 17 16 15 14 13 12
XR-2277/XR-2278
2 3 4S6 7
~I
11
8
10
9
Cl
o--ti +
GND
R3 liiN RL ------- RL
R4
Rl
r
R2 RS
l C2
Figure 2. Generalized Test Circuit
1-247
R1 = soon
R2 = 27KH
R3 = 330KH
R4 = 10KH
Rs = 10Kn
C 1 = 2.2/LF
C2 = 10Jl.F
RL = 200H


Part Number XR-2277
Description Dot and Bar Graph Display Generators
Maker Exar
Total Page 5 Pages
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