MAX445 Maxim, MAX445 Datasheet - Page 6

• Manufacturer Part Number: MAX445
• Description: Low-Cost / High-Resolution / 200MHz Video CRT Driver
• Manufacturer: Maxim

Table 1. Peaking Networks
(R
Inductors L1, L2, and L3 should be air or ferrite-core
coils with self-resonant frequencies higher than
500MHz.
The MAX445 can dissipate a large amount of power
depending on speed and load-driving requirements. The
power-tab package provides a low thermal resistance
path from the chip to an external heatsink. Be sure the
board design provides sufficient heatsinking capacity for
the intended operating range. When mounting to a chas-
sis, it should be noted that the device tab is attached to
V
ground through a thermally conductive insulator.
It is highly recommended that the external heatsink be
connected to ground, since an arc or electrostatic dis-
charge entering the heatsink may break down or
bypass the tab insulator and damage the device. Also,
the grounded heatsink to package tab capacitance will
help to bypass the V
be to bypass the heatsink to ground with a 0.01µF
capacitor with no tab insulator. Inadvertently shorting
the package tab to ground for less than 10 seconds will
Low-Cost, High-Resolution, 200MHz
Video CRT Driver
Figure 2. Typical Rise/Fall Time vs. Loading, with Peaking Network Optimized for Load Capacitance
6
C
EE
L
L
10
12
_______________________________________________________________________________________
2
4
6
8
(pF)
(-10.5V). This tab should be electrically isolated from
= 200Ω, R
L3 (nH)
100
200
175
150
125
100
20
50
75
0
0
2
S
L1 (nH)
= 100Ω)
100
120
4
EE
20
40
60
80
LOAD CAPACITANCE (pF)
supply. Another option would
6
Thermal Environment
L2 (nH)
120
180
240
300
360
60
8
C
10
B
0.4
0.8
1.1
1.5
2.0
2.2
(pF)
12
t
R
1.7
1.9
2.1
2.3
2.7
3.0
(ns)
not cause component damage. Junction-to-case ther-
mal resistance is rated at 6°C/W for the power-tab DIP
package. Table 2 shows the relationship of output volt-
age and duty cycle to total power.
Table 2. Power Dissipation at V
and Load Resistor = 200Ω
Due to the extremely high-speed performance of the
MAX445, layout design precautions are required to
realize the display driver’s full high-speed capability.
The precautions are as follows:
1) A printed circuit board with a good, unbroken, low-
2) Place a decoupling capacitor (0.01µF ceramic) as
3) Pay close attention to the decoupling capacitors’
4) On the inputs and outputs, keep lead lengths short
5) Solder the MAX445 directly to the printed circuit
Output Level
Relative to
Black (V)
inductance ground plane is required.
close to V
resonant frequency and keep leads short.
to avoid unwanted parasitic feedback around the
display driver.
board. Do not use sockets.
35
35
50
0
3.0
2.5
2.0
1.5
1.0
2
CC
Duty Cycle
as possible.
4
LOAD CAPACITANCE (pF)
Circuit Layout and Bypassing
(%)
100
80
80
0
6
IC Power
8
(W)
1.6
7.8
6.5
5.6
10
Load Power
12
10.0
(W)
6.1
4.9
AA
0
= 70V
Total
13.9
11.4
15.6
(W)
1.6