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PDF LT1969 Data sheet ( Hoja de datos )
| Número de pieza | LT1969 | |
| Descripción | Adjustable Current Operational Amplifier | |
| Fabricantes | Linear | |
| Logotipo |  |
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LT1969
Dual 700MHz, 200mA,
Adjustable Current Operational Amplifier
FEATURES
s 700MHz Gain Bandwidth
s ±200mA Minimum IOUT
s Adjustable Quiescent Current
s Low Distortion: –72dBc at 1MHz, 4VP-P, 25Ω, AV = 2
s Stable in AV ≥ 10, Simple Compensation for AV < 10
s ±4.3V Minimum Output Swing, VS = ±6V, RL = 25Ω
s Stable with 1000pF Load
s 6nV/√Hz Input Noise Voltage
s 2pA/√Hz Input Noise Current
s 4mV Maximum Input Offset Voltage
s 4µA Maximum Input Bias Current
s 400nA Maximum Input Offset Current
s ±4.5V Minimum Input CMR, VS = ±6V
s Specified at ±6V, ±2.5V
U
APPLICATIO S
s DSL Modems
s xDSL PCI Cards
s USB Modems
s Line Drivers
DESCRIPTIO
The LT®1969 is an adjustable current version of the
popular LT1886, a 200mA minimum output current, dual
op amp with outstanding distortion performance. The
adjustable current feature is highly desirable in applica-
tions where minimum power dissipation is required while
still being able to provide adequate line termination.
At nominal supply current, the amplifiers are gain of 10
stable and can easily be compensated for lower gains. The
LT1969 features balanced high impedance inputs with
4µA input bias current and 4mV maximum input offset
voltage. Single supply applications are easy to implement
and have lower total noise than current feedback amplifier
implementations.
The output drives a 25Ω load to ±4.3V with ±6V supplies.
On ±2.5V supplies, the output swings ±1.5V with a 100Ω
load. The amplifier is stable with a 1000pF capacitive load
making it useful in buffer and cable driver applications.
The LT1969 is manufactured on Linear Technology’s
advanced low voltage complementary bipolar process and
is available in a thermally enhanced MS10 package
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Single 12V Supply ADSL Modem Line Driver
12V
0.1µF
IN +
10k 20k
+
1/2 LT1969
–
909Ω
12.4Ω
100Ω
1:2*
*COILCRAFT X8390-A
OR EQUIVALENT
1µF 10k 20k
0.1µF
IN –
1µF 100Ω
909Ω
–
1/2 LT1969
+
12.4Ω
100Ω
CTRL1 CTRL2
67
IQ ON = 14mA
IQ LOW POWER = 2mA
IQ STANDBY = 600µA
13k 49.9k STANDBY ON
STANDBY
LOW POWER ON
LOGIC
OUTPUT
1969 TA01a
ADSL Modem Line Driver Distortion
–60
VS = 12V
AV = 10
f = 200kHz
–70 100Ω LINE
1:2 TRANSFORMER
HD2
–80
–90
HD3
–100
0 2 4 6 8 10 12 14 16
LINE VOLTAGE (VP-P)
1969 TA01b
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
13k resistor from CTRL1 to V – and a 49.9k resistor from CTRL2 to V –
Supply Current vs Temperature
20
18
16
VS = ±6V
14
12
VS = ±2.5V
10
8
6
4
2
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1969 G01
Input Bias Current
vs Temperature
3.5 IB = (IB+ – IB–)/2
3.0
2.5
2.0
1.5
VS = ±6V
1.0
VS = ±2.5V
0.5
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1969 G43
Output Saturation Voltage
vs Temperature
V+
VS = ±2.5V
–0.5 RL = 100Ω
–1.0
150mA
–1.5
200mA
1.5 200mA
1.0
150mA
RL = 100Ω
0.5
V–
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1969 G45
Input Common Mode Range
vs Supply Voltage
V+
–0.1
–0.2
–0.3
1.5
1.0
0.5 TA = 25°C
V – ∆VOS > 1mV
0 2 4 6 8 10 12
TOTAL SUPPLY VOLTAGE (V)
14
1969 G02
Input Noise Spectral Density
100
TA = 25°C
AV = 101
100
10 10
en
in
11
10 100 1k 10k 100k
FREQUENCY (Hz)
1969 G04
Output Short-Circuit Current
vs Temperature
1000
900
800
SOURCE
VS = ±6V
700 SOURCE
600 VS = ±2.5V
500
400
SINK
300
200
VS = ±6V
SINK
VS = ±2.5V
100
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
1969 G46
LT1969
Input Bias Current
vs Input Common Mode Voltage
3.0 TA = 25°C
IB = (IB+ + IB–)/2
2.5
2.0
VS = ±6V
1.5
1.0 VS = ±2.5V
0.5
0
–6 –4 –2 0 2 4
INPUT COMMON MODE VOLTAGE (V)
6
1969 G03
Output Saturation Voltage
vs Temperature
V+
VS = ±6V
–0.5
RL = 100Ω
–1.0
150mA
–1.5
200mA
1.5 200mA
1.0
150mA
RL = 100Ω
0.5
V–
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1969 G44
Settling Time vs Output Step
6
VS = ±6V
4
10mV
1mV
2
0
–2
–4
–6
0
10mV
1mV
10 20 30 40 50
SETTLING TIME (ns)
60
1886 G05
5
5 Page 
LT1969
APPLICATIO S I FOR ATIO
were taken in still air on 3/32" FR-4 board with 2oz copper.
This data can be used as a rough guideline in estimating
thermal resistance. The thermal resistance for each appli-
cation will be affected by thermal interactions with other
components as well as board size and shape.
Table 1. Fused 10-Lead MSOP Package
COPPER AREA
TOPSIDE* BACKSIDE
(mm 2)
(mm 2)
BOARD AREA THERMAL RESISTANCE
(mm2) (JUNCTION-TO-AMBIENT)
540 540
2500
110°C/ W
100 100
2500
120°C/ W
100 0
2500
130°C/ W
30 0
2500
135°C/ W
00
2500
140°C/ W
*Device is mounted on topside.
Calculating Junction Temperature
The junction temperature can be calculated from the
equation:
TJ = (PD)(θJA) + TA
TJ = Junction Temperature
TA = Ambient Temperature
PD = Device Dissipation
θJA = Thermal Resistance (Junction-to-Ambient)
As an example, calculate the junction temperature for the
circuit in Figure 1 assuming an 70°C ambient temperature.
The device dissipation can be found by measuring the
supply currents, calculating the total dissipation and then
subtracting the dissipation in the load.
The dissipation for the amplifiers is:
PD = (63.5mA)(12V) – (4V/√2)2/(50) = 0.6W
The total package power dissipation is 0.6W. When a 2500
sq. mm PC board with 540 sq. mm of 2oz copper on top
and bottom is used, the thermal resistance is 110°C/W.
The junction temperature TJ is:
TJ = (0.6W)(110°C/W) + 70°C = 136°C
The maximum junction temperature for the LT1969 is
150°C so the heat sinking capability of the board is
adequate for the application.
If the copper area on the PC board is reduced to 0 sq. mm
the thermal resistance increases to 140°C/W and the
junction temperature becomes:
TJ = (0.6W)(140°C/W) + 70°C = 154°C
which is above the maximum junction temperature indi-
cating that the heat sinking capability of the board is
inadequate and should be increased.
6V
+
–
909Ω
100Ω
CTRL1
6
CTRL2
7
100Ω
13k 49.9k
–
+
1K
–6V –6V
–6V
4V
50Ω
–4V
f = 1MHz
1969 F01
Figure 1. Thermal Calculation Example
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LT1969.PDF ] | |
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