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LT1994
In general, the die temperature can be estimated from
the ambient temperature TA, and the device power dis-
sipation PD:
TJ = TA+ + PD θJA
The power dissipation in the IC is a function of the supply
voltage, the output voltage, and the load resistance. For
fully differential output ampliers at a given supply voltage
(±VCC), and a given differential load (RLOAD), the worst-
case power dissipation PD(MAX) occurs at the worst-case
quiescent current (IQ(MAX) = 20.5mA) and when the load
current is given by the expression:
I
V
R
LOAD
CC
LOAD
=
The worst-case power dissipation in the LT1994 at
I
V
R
LOAD
CC
LOAD
=
is:
PV
I
R
V
R
VI
DMAX
CC
LOAD
Q MAX
LOAD
CC
LOAD
CC
QMAX
()
=+
()
=+
2
–
Example: A LT1994 is mounted on a circuit board in a
MSOP-8 package (
θJA = 140°C/W), and is running off of
±5V supplies driving an equivalent load (external load plus
feedback network) of 75
Ω. The worst-case power that
would be dissipated in the device occurs when:
P
V
R
VI
V
DMAX
CC
LOAD
CC
QMAX
()
=+
2
5
75
25
Ω
.
17 5
0 54
MA
W
=
The maximum ambient temperature the 8-lead MSOP is
allowed to operate under these conditions is:
TA = TJMAX – PD θJA = 150°C – (0.54W)
(140°C/W) = 75°C
To operate the device at higher ambient temperature,
connect more copper to the V– pin to reduce the thermal
resistance of the package as indicated in Table 1.
Table 1. LT1994 MSOP Package Thermal Resistivity
COPPER AREA
TOPSIDE (mm2)
COPPER AREA
BACKSIDE (mm2)
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
00
140
30
0
135
100
0
130
100
120
540
110
Layout Considerations
Because the LT1994 is a high speed amplier, it is sensitive
to both stray capacitance and stray inductance. Compo-
nents connected to the LT1994 should be connected with
as short and direct connections as possible. A low noise,
low impedance ground plane is critical for the highest
performance. In single-supply applications, high quality
surface mount 1μF and 0.1μF ceramic bypass capacitors
with minimum PCB trace should be used directly across
the power supplies V+ to V–. In split supply applications,
high quality surface mount 1μF and 0.1μF ceramic bypass
capacitors should be placed across the power supplies
V+ to V–, and individual high quality surface mount 0.1μF
bypass capacitors should be used from each supply to
ground with direct (short) connections.
Any stray parasitic capacitance to ground at the summing
junctions, IN+ and IN– should be kept to an absolute mini-
mum even if it means stripping back the ground plane
away from any trace attached to this node. This becomes
especially true when the feedback resistor network uses
resistor values >500
Ω in circuits with RF = RI. Excessive
peaking in the frequency response can be mitigated by
adding small amounts of feedback capacitance around RF
(2pF to 5pF). Always keep in mind the differential nature of
the LT1994, and that it is critical that the output impedances
seen by both outputs (stray or intended) should be as bal-
anced and symmetric as possible. This will help preserve
the natural balance of the LT1994, which minimizes the
generation of even order harmonics, and preserves the
rejection of common mode signals and noise.
It is highly recommended that the VOCM pin be either hard
tied to a low impedance ground plane (in split supply
applications) or bypassed to ground with a high quality
APPLICATIONS INFORMATION
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT1994HDD#PBF | 功能描述:IC DIFF AMP/DRIVER LN-LD 8-DFN RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:50 系列:- 放大器類型:通用 電路數(shù):2 輸出類型:滿擺幅 轉(zhuǎn)換速率:1.8 V/µs 增益帶寬積:6.5MHz -3db帶寬:4.5MHz 電流 - 輸入偏壓:5nA 電壓 - 輸入偏移:100µV 電流 - 電源:65µA 電流 - 輸出 / 通道:35mA 電壓 - 電源，單路/雙路(±):1.8 V ~ 5.25 V，±0.9 V ~ 2.625 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬） 供應商設備封裝:10-MSOP 包裝:管件 |
| LT1994HDD#TR | 制造商:Linear Technology 功能描述:DIFF-AMPLIFIER, 70MHZ, 65V/US, DFN-8, No. of Amplifiers:1, Input Offset Voltage:2mV, Bandwidth:70MHz, Amplifier Case Style:DFN, No. of Pins:8, Supply Voltage Range:2.375V to 12.6V, Slew Rate:65V/s, Supply Current:14.8mA, MSL:- , RoHS Compliant: No |
| LT1994HDD#TRPBF | 功能描述:IC DIFF AMP/DRIVER LN-LD 8-DFN RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:50 系列:- 放大器類型:通用 電路數(shù):2 輸出類型:滿擺幅 轉(zhuǎn)換速率:1.8 V/µs 增益帶寬積:6.5MHz -3db帶寬:4.5MHz 電流 - 輸入偏壓:5nA 電壓 - 輸入偏移:100µV 電流 - 電源:65µA 電流 - 輸出 / 通道:35mA 電壓 - 電源，單路/雙路(±):1.8 V ~ 5.25 V，±0.9 V ~ 2.625 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬） 供應商設備封裝:10-MSOP 包裝:管件 |
| LT1994IDD | 制造商:Linear Technology 功能描述:SP Amp DIFF AMP Single R-R O/P ±6.3V/12.6V 8-Pin DFN EP |
| LT1994IDD#PBF | 功能描述:IC DIFF AMP/DRIVER LN 8-DFN RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 產(chǎn)品培訓模塊:Differential Circuit Design Techniques for Communication Applications 標準包裝:1 系列:- 放大器類型:RF/IF 差分 電路數(shù):1 輸出類型:差分 轉(zhuǎn)換速率:9800 V/µs 增益帶寬積:- -3db帶寬:2.9GHz 電流 - 輸入偏壓:3µA 電壓 - 輸入偏移:- 電流 - 電源:40mA 電流 - 輸出 / 通道:- 電壓 - 電源，單路/雙路(±):3 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:16-VQFN 裸露焊盤，CSP 供應商設備封裝:16-LFCSP-VQ 包裝:剪切帶 (CT) 產(chǎn)品目錄頁面:551 (CN2011-ZH PDF) 其它名稱:ADL5561ACPZ-R7CT |
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