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PDF MP8820 Data sheet ( Hoja de datos )
| Número de pieza | MP8820 | |
| Descripción | 8-Bit Analog-to-Digital Converter | |
| Fabricantes | Exar Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MP8820 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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FEATURES
• Precision 7–Bit Plus Sign ADC
• 8 Channel Analog Mux
• Single Reference to GND
• Input Referenced to User Supplied VMID
• DNL= ±1/2 LSB, INL=± 1 LSB
• Single Supply: 5 V
• ESD Protection: 2000 V
MP8820
8-Bit Analog-to-Digital Converter
with an 8-Channel MUX
APPLICATIONS
• Servo Control
• Low Cost Audio Control
• Voice Acquisition
GENERAL DESCRIPTION
The MP8820 is a precision 1.6 MHz sampling 7-bit plus sign
Analog-to-Digital Converter with an eight channel input mux and
µP interface. The device has internal circuitry which receives
the user supplied reference voltages VREF(+) and VREF(–), and
generates the ADC reference voltages VMID (VREF(+) –
VREF(–)). Since VREF(+) is internally buffered and VREF(–) is gen-
erally ground, this structure allows the user to easily generate an
input range biased about a user-supplied VMID from a grounded
reference source.
The internal ADC reference voltages are capable of swinging
to within 0.5 V of the supply rails, giving the MP8820 a wide
range over which the effective channel gain can be adjusted.
The MP8820 uses a two-step flash conversion technique.
The first section determines the sign and the 3 MSBs while the
second segment converts the 4 LSBs. The ADC conversion be-
gins when WR goes low and the data is valid 500 ns after the
rising edge of WR. The MP8820 operates from a single 5V sup-
ply and consumes only 175mW of power.
Specified for operation over the industrial (–40 to +85°C)
temperature range, the MP8820 is available in Surface Mount
(SOIC) and Shrunk Small Outline (SSOP) packages.
SIMPLIFIED BLOCK DIAGRAM
VDD
VMID
VREF(+)
VREF(–)
+
–
G=1
+
– G=1
+
– G=1
AIN0-AIN7
8
8:1 MUX
T/H
VRT AIN
VMID
8-Bit
ADC
VRB
Control
3
8
A0-A2
DB0-DB7
Rev. 1.00
GND
WR
1
1 page  
MP8820
THEORY OF OPERATION
The defining feature of the MP8820 is that it digitizes a bipolar
input signal centered around a given voltage, VMID. The peak to
peak swing of AIN is defined by the two input reference voltages,
VREF(+) and VREF(–).
The MP8820 takes in the center voltage and the two refer-
ence voltages and moves the resistor ladder endpoints VRT and
VRB of the ADC around VMID by (VREF(+) – VREF(–)). In this
way, a unipolar to bipolar translation can take place without hav-
ing to use both a positive and negative supply. The center volt-
age acts as a bipolar zero and signals that moves below it are
considered negative and signals that exceed it are taken to be
positive. The block diagram is shown in Figure 1.
VMID
VREF(+)
VREF(–)
VDD
+
–
G=1
+
– G=1
+
– G=1
AIN0-AIN7
8
8:1 MUX
T/H
VRT AIN
VMID
8-Bit
ADC
VRB
Control
3
8
A0-A2
DB0-DB7
GND
WR
Figure 1. MP8820 Block Diagram
Unlike a unipolar system where one end of the ADC’s resistor
ladder is modulated above an offset voltage, both ends of the
MP8820’s reference chain expand or contract around a fixed
VMID. The maximum positive full scale voltage is VRT = VMID +
(VREF(+) – VREF(–)). The maximum negative full scale voltage is
VRB = VMID – (VREF(+) – VREF(–)). This type of translation is par-
ticularly useful in single supply applications where the input is
centered about user specified VMID.
The ideal transfer characteristic of the MP8820 is shown in
Figure 2. An actual transfer characteristic with associated error
terms is shown in Figure 3.
00000000
CODE
OUT
VIN
VRT = VMID + (VREF(+) – VREF(–))
11111111
VRB = VMID = (VREF(+) – VREF(–))
Figure 2. Ideal Transfer Characteristics
Rev. 1.00
5
5 Page 
MP8820
28 LEAD SHRINK SMALL OUTLINE PACKAGE
(SSOP)
A28
D
28
1
Seating
Plane
e
15
EH
14
B A1
C
SYMBOL
A
A1
B
C
D
E
e
H
L
α
MILLIMETERS
MIN MAX
1.73 2.05
0.05 0.21
0.20 0.40
0.13 0.25
10.07 10.40
5.20 5.38
0.65 BSC
7.65 8.1
0.45 0.95
0° 8°
INCHES
MIN MAX
0.068 0.081
0.002 0.008
0.008 0.016
0.005 0.010
0.397 0.409
0.205 0.212
0.0256 BSC
0.301 0.319
0.018 0.037
0° 8°
A
α
L
Rev. 1.00
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MP8820.PDF ] | |
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