LM2413 National Semiconductor Corporation, LM2413 Datasheet - Page 5

• Manufacturer Part Number: LM2413
• Description: LM2413 - Monolithic Triple 4 NS CRT Driver, Package: to 220, Pin Nb=11
• Manufacturer: National Semiconductor Corporation

Application Hints
OPTIMIZING TRANSIENT RESPONSE
Referring to Figure 9 , there are three components (R1, R2
and L1) that can be adjusted to optimize the transient re-
sponse of the application circuit. Increasing the values of R1
and R2 will slow the circuit down while decreasing over-
shoot. Increasing the value of L1 will speed up the circuit as
well as increase overshoot. It is very important to use induc-
tors with very high self-resonant frequencies, preferably
above 300 MHz. The values shown in Figure 9 can be used
as a good starting point for the evaluation of the LM2413.
Effect of Load Capacitance
The output rise and fall times as well as overshoot will vary
as the load capacitance varies. The values of the output cir-
cuit (R1, R2 and L1 in Figure 9 ) should be chosen based on
the nominal load capacitance. Once this is done the perfor-
mance of the design can be checked by varying the load
based on what the expected variation will be during produc-
tion.
Effect of Offset
Figure 5 shows the variation in rise and fall times when the
output offset of the device is varied from 35 to 55 VDC. The
rise and fall times show about the same overall variation.
The slightly faster rise and fall times are fastest near the cen-
ter point of 45V, making this the optimum operating point. At
the low and high output offset range, the characteristic of
rise/fall time is slower due to the saturation of Q3 and Q4.
The recovery time of the output transistors takes longer com-
ing out of saturation thus slows down the rise and fall times.
THERMAL CONSIDERATIONS
Figure 4 shows the performance of the LM2413 in the test
circuit shown in Figure 2 as a function of case temperature.
Figure 4 shows that both the rise and fall times of the
LM2413 become slightly longer as the case temperature in-
creases from 40˚C to 100˚C. Please note that the LM2413 is
never to be operated over a case temperature of 100˚C.
In addition to exceeding the safe operating temperature, the
rise and fall times will typically exceed 3.7/4.4 ns.
Figure 6 shows that total power dissipation of the LM2413
vs. Frequency when all three channels of the device are driv-
ing an 8 pF load. Typically the active time is about 72% of the
total time for one frame. Worst-case power dissipation is
when a one on, one off pixel is displayed over the active time
of the video input. This is the condition used to measure the
total power dissipation of the LM2413 at different input fre-
quencies. Figure 6 gives all the information a monitor de-
signed normally needs for worst case power dissipation.
FIGURE 9. One Channel of the LM2413 with the Recommended Arc Protection Circuit
(Continued)
5
However, if the designer wants to calculate the power dissi-
pation for an active time different from 72%, this can be done
using the information in Figure 14 . The recommended input
black level voltage is 1.9V. From Figure 14 , if a 1.9V input is
used for the black level, then power dissipation during the in-
active video time is 1.95W. This includes both the 80V and
12V supplies.
If the monitor designer chooses to calculate the power dissi-
pation for the LM2413 using an active video time different
from 72%, then he needs to use the following steps when us-
ing a 1.9V input black level:
1. Multiply the black level power dissipation, 1.95W, by
2. Choose the maximum frequency to be used. A typical
3. Subtract the 0.6W from the power dissipation from Fig-
4. Divide the result from step 3 by 0.72. For 90 MHz, the re-
5. Multiply the result in 4 by the new active time percent-
6. Multiply 1.95W by the new inactive time.
7. Add together the results of steps 5 and 6. This is the ex-
The LM2413 case temperature must be maintained below
100˚C. If the maximum expected ambient temperature is
70˚C and the maximum power dissipation is 12.2W ( Figure
6 ) then a maximum heat sink thermal resistance can be cal-
culated:
This example assumes a capacitive load of 8 pF and no re-
sistive load.
TYPICAL APPLICATION
A typical application of the LM2413 is shown in Figure 10 .
Used in conjunction with an LM1283, a complete video chan-
nel from monitor input to CRT cathode can be achieved. Per-
formance is excellent for resolutions up to 1600 x 1200 and
pixel clock frequencies at 180 MHz. Figure 10 is the sche-
matic for the NSC demonstration board that can be used to
evaluate the LM1283/2413 combination in a monitor.
0.28, the result is 0.6W.
application would use 90 MHz, or a 180 MHz pixel clock.
The power dissipation is 12.4W.
ure 6 . For 100 MHz this would be 12.4 − 0.6 = 11.8W.
sult is 16.4W
age.
pected power dissipation for the LM2413 in the design-
er’s application.
DS101275-10
DS101275-11
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