MAX108 Maxim, MAX108 Datasheet - Page 25

• Manufacturer Part Number: MAX108
• Description: 5V / 1.5Gsps / 8-Bit ADC with On-Chip 2.2GHz Track/Hold Amplifier
• Manufacturer: Maxim

Table 7. Thermal Performance for
MAX108 With or Without Heatsink
The MAX108 has been modeled to determine the ther-
mal resistance from junction to ambient. Table 7 lists
the ADC’s thermal performance parameters:
Ambient Temperature:
Heatsink Dimensions:
PC Board Size and Layout:
Aavid Engineering and IERC provide open-tooled, low-
profile heatsinks, fitting the 25mm x 25mm ESBGA
package.
Aavid Engineering, Inc.
Phone: [phone]
Heatsink Catalog No.: 335224B00032
Heatsink Dimensions: 25mm x 25mm x 10mm
International Electronic Research Corporation (IERC)
Phone: [phone]
Heatsink Catalog No.: BDN09-3CB/A01
Heatsink Dimensions: 23.1mm x 23.1mm x 9mm
Grounding and power-supply decoupling strongly influ-
ence the MAX108’s performance. At a 1.5GHz clock
frequency and 8-bit resolution, unwanted digital
crosstalk may couple through the input, reference,
power-supply, and ground connections and adversely
influence the dynamic performance of the ADC.
Therefore, closely follow the grounding and power-sup-
ply decoupling guidelines (Figure 22).
(linear ft/min)
AIRFLOW
200
400
800
0
Bypassing/Layout/Power Supply
______________________________________________________________________________________
HEATSINK
WITHOUT
16.5
14.3
12.5
13
On-Chip 2.2GHz Track/Hold Amplifier
MAX108
Heatsink Manufacturers
T
25mm x 25mm x 10mm
4 in. x 4 in.
2 Signal Layers
2 Power Layers
A
Thermal Performance
= +70°C
JA
WITH HEATSINK
(°C/W)
12.5
9.4
8.3
7.4
±5V, 1.5Gsps, 8-Bit ADC with
Maxim strongly recommends using a multilayer printed
circuit board (PCB) with separate ground and power-
supply planes. Since the MAX108 has separate analog
and digital ground connections (GNDA, GNDI, GNDR,
and GNDD, respectively), the PCB should feature sep-
arate analog and digital ground sections connected at
only one point (star ground at the power supply). Digital
signals should run above the digital ground plane, and
analog signals should run above the analog ground
plane. Keep digital signals far away from the sensitive
analog inputs, reference inputs, and clock inputs. High-
speed signals, including clocks, analog inputs, and
digital outputs, should be routed on 50Ω microstrip
lines, such as those employed on the MAX108 evalua-
tion kit.
The MAX108 has separate analog and digital power-
supply inputs: V
and V
bution, bandgap reference, and reference amplifier;
V
V
based circuit sections; and V
logic circuits of the data converter.
The MAX108 V
open while the part is being powered up. To avoid this
condition, add a high-speed Schottky diode (such as a
Motorola 1N5817) between V
prevents the device substrate from forward biasing,
which could cause latchup.
Figure 21. MAX108 Thermal Performance
CC
CC
O (+3V to V
A (+5V) to supply the ADC’s comparator array;
CC
I (+5V) to power the T/H amplifier, clock distri-
18
16
14
12
10
8
6
0
THERMAL RESISTANCE vs. AIRFLOW
EE
100
CC
EE
D) to establish power for all PECL-
supply contacts must not be left
(-5V analog and substrate supply)
200
AIRFLOW (linear ft./min.)
300 400 500 600 700 800
WITH HEATSINK
EE
CC
and GNDI. This diode
D (+5V) to supply all
WITHOUT
HEATSINK
25