MAX108 Datasheet, PDF (25/32 Pages) Maxim Integrated Products – ±5V, 1.5Gsps, 8-Bit ADC with On-Chip 2.2GHz Track/Hold Amplifier

±5V, 1.5Gsps, 8-Bit ADC with
On-Chip 2.2GHz Track/Hold Amplifier
Table 7. Thermal Performance for
MAX108 With or Without Heatsink
AIRFLOW
(linear ft/min)
MAX108 θ_JA (°C/W)
WITHOUT
HEATSINK
WITH HEATSINK
0
16.5
12.5
200
14.3
9.4
400
13
8.3
800
12.5
7.4
Thermal Performance
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:
T_A = +70°C
Heatsink Dimensions:
25mm x 25mm x 10mm
PC Board Size and Layout: 4 in. x 4 in.
2 Signal Layers
2 Power Layers
Heatsink Manufacturers
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
Bypassing/Layout/Power Supply
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).
THERMAL RESISTANCE vs. AIRFLOW
18
16
14
WITHOUT
HEATSINK
12
10
WITH HEATSINK
8
6
0 100 200 300 400 500 600 700 800
AIRFLOW (linear ft./min.)
Figure 21. MAX108 Thermal Performance
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_EE (-5V analog and substrate supply)
and V_CCI (+5V) to power the T/H amplifier, clock distri-
bution, bandgap reference, and reference amplifier;
V_CCA (+5V) to supply the ADC’s comparator array;
V_CCO (+3V to V_CCD) to establish power for all PECL-
based circuit sections; and V_CCD (+5V) to supply all
logic circuits of the data converter.
The MAX108 V_EE supply contacts must not be left
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_EE and GNDI. This diode
prevents the device substrate from forward biasing,
which could cause latchup.
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