mp8798 Exar Corporation, mp8798 Datasheet - Page 11

• Manufacturer Part Number: mp8798
• Description: Cmos Very Low Power, 1 Msps 10-bit Analog-to-digital Converter With 4-channel Mux
• Manufacturer: Exar Corporation

APPLICATION NOTES
formance of the MP8798.
1. All signals should not exceed AV
2. Any input pin which can see a value outside the absolute
3. The design of a PC board will affect the accuracy of MP8798.
4. The analog input signal (V
5. The analog input should be driven by a low impedance (less
6. Analog and digital ground planes should be substantial and
C
C
R
The following information will be useful in maximizing the per-
1
2
T
or DV
maximum ratings (AV
should be protected by diode clamps (HP5082-2835) from
input pin to the supplies. All MP8798 inputs have input pro-
tection diodes which will protect the device from short tran-
sients outside the supply ranges.
Use of wire wrap is not recommended.
properly routed and terminated. It should be shielded from
the clock and digital outputs so as to minimize cross coupling
and noise pickup.
than 50
common at one point only. The ground plane should act as a
= 4.7 or 10 F Tantalum
= 0.1 F Chip Cap or low inductance capacitor
= Clock Transmission Line Termination
Rev. 3.00
DD
+0.5 V or DGND –0.5 V.
Reference
Voltage
Source
DD
+
–
or DV
IN
) is quite sensitive and should be
1 of 4
DD
C
DD
1
+0.5 V or AGND –0.5 V)
A
+0.5 V or AGND –0.5 V
IN
C
Figure 14. Typical Circuit Connections
2
Buffer
C
1
50 to 100W
Isolation of
Resistive
C
2
Z 100W
11
C
1A,
7. DV
8. DV
9. Each power supply and reference voltage pin should be
10. The digital output should not drive long wires. The capacitive
AV
A
A
C
IN1
IN4
DD
shield for parasitics and not a return path for signals. To re-
duce noise levels, use separate low impedance ground
paths. DGND should not be shared with other digital cir-
cuitry . If separate low impedance paths cannot be provided,
DGND should be connected to AGND next to the MP8798.
avoid conversion errors caused by digital supply transients.
DV
the MP8798.
the N – doped silicon substrate. Any DC voltage difference
between DV
currents.
decoupled with a ceramic (0.1 F) and a tantalum (10 F) ca-
pacitor as close to the device as possible.
coupling and reflection will contribute noise to the conver-
sion. When driving distant loads, buffers should be used.
100 resistors in series with the digital outputs in some ap-
plications reduces the digital output disruption of A
2A
+5 V
V
1/2 R
V
V
(Substrate)
AGND
REF(+)
REF(–)
REF1(–)
DD
DD
DD
MP8798
for the MP8798 should be connected to AV
and AV
should not be shared with other digital circuitry to
DGND
DD
CLK
DD
and AV
are connected inside the MP8798 through
C
DV
1D,
R
DD
T
C
WR
A0
A1
DD
2D
will cause undesirable internal
OFW
DB9 - DB0
MP8798
DD
IN
next to
.