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KH561AK/AM 参数 Datasheet PDF下载

KH561AK/AM图片预览
型号: KH561AK/AM
PDF下载: 下载PDF文件 查看货源
内容描述: 宽带,低失真驱动器放大器 [Wideband, Low Distortion Driver Amplifier]
分类和应用: 驱动器放大器
文件页数/大小: 13 页 / 338 K
品牌: CADEKA [ CADEKA MICROCIRCUITS LLC. ]
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DATA SHEET  
KH561  
Case Temperature  
4572).  
Tc  
As an example of calculating the maximum internal junc-  
tion temperatures, consider the circuit of Figure 1 driving  
±2.5V, 50% duty cycle, square wave into a 50load.  
Case to Ambient  
θ
ca  
20°C/W  
200°C/W  
Termal Impedance  
Tj(t)  
Pt  
Tj(q)  
TA  
Pq  
Pcircuit  
4105  
Ambient  
Temperature  
Req = 50Ω  
= 45.6Ω  
5 1  
Figure 10: Thermal Model  
I = V / R total output current  
I = 2.5V / 45.6Ω = 54.9mA  
(
)
o
o
o
eq  
2
2
1
IT =  
54.9mA + 54.9mA + .06  
= 68.1mA  
(
)
(
)
2
R A  
f
L
withR = R  
total load  
eq  
L
P = 68.1mA 15 2.5 0.7 15.368.1mA = 733mW  
A 1  
[
]
T
L
total power in both sides of the output stage  
2
2
1
I =  
I +  
I + .06  
o
(
)
t
o
P = 0.2 68.1mA 15 1.4 17.368.1mA = 169mW  
2
[
]
q
total power in both sides of hottest junctions  
prior to output stage  
total internal output stage current  
P = I 1.4 17.3I output stage power  
V
(
)
t
t
CC  
t
Pcircuit = 1.3 15 2 68.1mA 54.9mA +19.2mA  
(
)
[
]
733mW 169mW = 1.058W  
power in the remainder of circuit  
P = 0.2 I  
V
V 0.7 15.3I  
(
)
q
t
CC  
o t  
power in hottest internal junction  
prior to output stage  
With these powers and TA = 25°C and θca = 35°C / W  
T = 25°C + .733 +.169 +1.058 35 = 94°C  
(
)
P
= 1.3 V  
2 I I +19.2mA P P  
q
c
(
)
circuit  
CC  
t
o
t
case temperature  
power in remainder of circuit [note V = | V |]  
CC  
CC  
From this, the hottest internal junctions may be found as  
Note that the P and P equations are written for positive  
t
q
T t = 94°C + 1 .733 20 = 101°C output stage  
V . Absolute values of -V , V , and I , should be used  
j( )  
(
)
o
CC  
o
o
2
for a negative going V . since we are only interested in  
o
T q = 94°C + 1 .169 200 = 111°C  
j( )  
delta V’s. For bipolar swings, the two powers for each  
output polarity are developed as shown above then  
ratioed by the duty cycle. Having the total internal power,  
as well as its component parts, the maximum junction  
temperature may be computed as follows.  
(
)
2
hottest internal junction  
Note that 1/2 of the total P and P powers were used  
T
a
here since the 50% duty cycle output splits the power  
evenly between the two halves of the circuit whereas the  
total powers were used to get case temperature.  
T = T + (P + P + P  
) θ Case Temperature  
ca  
c
A
q
T
circult  
θ
= 35°C/W for the KH561 with no heatsink in still air  
ca  
Even with the output current internally limited to 250mA,  
the KH561’s short circuiting capability is principally a  
thermal issue. Generally, the KH561 can survive short  
duration shorts to ground without any special effort. For  
protection against shorts to the ±15 volt supply voltages,  
it is very useful to reduce some of the voltage across the  
output stage transistors by using some external output  
T
= T + P 20°C/W  
c t  
j(t)  
output transistor junction temperature  
= T + P 200°C/W  
T
j(q)  
c
q
hottest internal junction temperature  
The Limiting Factor for Output Power is Maximum  
Junction Temperature  
Reducing  
θ
through either heatsinking and/or  
resistance, R , as shown in Figure 9.  
ca  
x
airflow can greatly reduce the junction temperatures.  
One effective means of heatsinking the KH561 is to use  
a thermally conductive pad under the part from the pack-  
age bottom to a top surface ground plane on the compo-  
Evaluation Board  
An evaluation board (part number 730019) for the KH561  
is available.  
nent side. Tests have shown a θ of 24°C in still air  
ca  
using a “Sil Pad” available from Bergquist (800-347-  
12  
REV. 1A January 2004