VP215 MITEL [Mitel Networks Corporation], VP215 Datasheet - Page 6

• Manufacturer Part Number: VP215
• Description: Dual 90MHz 6-Bit Analog to Digital Converter
• Manufacturer: MITEL [Mitel Networks Corporation]

Application Circuit
The supply connections are made using separate low noise
digital and analog power supplies and VCCD is further
isolated from VCCO using a 1.2 H inductor.
reduce any ripple at low frequencies which may distort the
ADC driver amplifier output, (see Fig.2.) The decoupling
capacitor value is determined by the required low frequency
performance of the system and can be obtained from the
following equation.
VP215
6
Layout And Grounding
consideration must be given to the PCB layout. High
performance can be obtained from the VP215 by tying all
grounds to a solid low impedance ground plane. Separate
analog and digital ground planes with a single common link
under the device can also be used to help reduce the
amount of digital noise fed back into the analog section of the
converter.
100nF ceramic capacitors close to the package pins to avoid
lead inductance effects and the decoupling on supply lines
CLKIN
VCCA
VINA
VINB
Fig.5 shows a typical applications circuit for the VP215.
As with all high speed A to D converters, careful
The VP215 should be decoupled with low impedance
The COMPA and COMPB pins must be decoupled to
47
C
Comp
50R
100n
=
F
1.2 H
50R
50R
in
75x10
C
x V
C
c
c
Ripple
- 6
C
C
100n
comp
100n
comp
100n
100n
Fig.5 Applications diagram
100n
1
2
3
4
5
6
7
8
9
10
11
12
13
14
VP215
system performance, e.g. If the analog input frequency F
10KHz a value of 0.75 F is required for C
frequencies, the coupling capacitors on pins 6 and 11 can be
calculated from the high pass filter corner frequency
equation,
should further be improved by using a 47 F tantalum
capacitor in parallel with a 100nF ceramic capacitor. If VCCA
is derived from VCCD, a small inductor should be used to
reduce digital noise on the analog power supply. Jitter and
noise on clock input pins must be minimised. Long clock
lines should therefore be avoided and all clock lines correctly
terminated. Cross talk of digital signals to the analog inputs
must also be prevented as sampling cross talk produces DC
offsets on the sampled data, for this reason analog inputs
should not be run next to clock or data lines. Device
connections to the ground plane should be as short as
possible.
A ripple voltage
To ensure effective A.C. coupling at low input
where
F
(R = Input Resistance, 25K typ. - 20K min)
c
= Lower -3dB corner frequency
28
27
26
25
24
23
22
21
20
19
18
17
16
15
F
c
100n
=
10mV is recommended for good
2 x
A Channel
B Channel
1
x RC
Data
Data
47
Comp
Analog Ground
Digital Ground
.
100n
VCCD
in
=