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PDF LM3460 Data sheet ( Hoja de datos )
| Número de pieza | LM3460 | |
| Descripción | Precision Controller for GTLp and GTL Bus Termination | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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May 1999
LM3460-1.2, -1.5
Precision Controller for GTLp and GTL Bus Termination
General Description
The LM3460 is a monolithic integrated circuit designed for
precision control of GTLplus and GTL Bus termination. This
controller is available in a tiny SOT23-5 package, and in-
cludes an internally compensated op amp, a bandgap refer-
ence, an NPN output transistor, and voltage setting resistors.
A trimmed precision bandgap voltage reference utilizes tem-
perature drift curvature correction for excellent voltage stabil-
ity over the operating range. The precision output control en-
ables the termination voltage to maintain tight regulation,
despite fast switching requirements on the bus.
The LM3460 controller is designed to be used with a high
current (> 7A) NPN pass transistor to provide the high cur-
rent needed for the bus termination. The wide bandwidth of
the feedback loop provides excellent transient response,
and greatly reduces the output capacitance required, thus
reducing cost and board space requirements.
Features
n Precision output (1%)
n Output voltage can be adjusted
n Extremely fast transient response in GTLp and GTL bus
termination
n Tiny SOT23-5 package
n Output voltage capability for GTL or GTLp
n Low temperature coefficient
Applications
n GTL bus termination (1.2V output 7A)
n GTLp bus termination (1.5V output 7A)
n Adjustable high-current linear regulator
Connection Diagram and Package Information
5-Lead Outline Package (M5)
Actual Size
DS012603-2
DS012603-1
*This resistor is not used on the LM3460-1.2.
LM3460 Functional Diagram
DS012603-3
*No internal connection, but should be soldered to PC board for best heat
transfer.
Top View
See NS package Number MA05B
Ordering Information
Voltage
1.5
1.5
1.2
1.2
Order Number
LM3460M5-1.5
LM3460M5X-1.5
LM3460M5-1.2
LM3460M5X-1.5
Package Marking
D06A
D06A
D09A
D09A
Supplied As
250 Unit Increments on Tape and Reel
3k Unit Increments on Tape and Reel
250 Unit Increments on Tape and Reel
3k Unit Increments on Tape and Reel
MARKING CODE: The first letter ″D″ identifies the part as a Driver, and the next two numbers define the voltage for the part. The fourth letter indicates the
grade, with ″A″ designating the prime grade of product.
AVAILABILITY: The SOT23-5 package is only available in quantity of 250 on tape and reel (designated by the letters ″M5″ in the part number), or in quantity
of 3000 on tape and reel (indicated by the letters ″M5X″ in the part number).
© 1999 National Semiconductor Corporation DS012603
www.national.com
1 page  
Product Description
The LM3460 is a shunt regulator designed for use as a pre-
cision control element in a feedback loop. The regulated out-
put voltage is sensed between the IN pin and GROUND pin
of the LM3460.
The output of the LM3460 sources current whenever the
voltage at the IN pin reaches the regulated voltage.
This current is used to cut off the drive to the external pass
trnasistor, which provides the negative feedback to force the
output voltage to be the same value as VREG.
If the voltage on the IN pin is forced above the VREG voltage,
the maximum voltage applied to the IN pin should not ex-
ceed 20V. In addition, an external resistor may be required
on the OUT pin to limit the maximum current to 20 mA.
Compensation
The inverting input of the error amplifier is brought out to sim-
plify closed-loop compensation. Typically, compensation is
provided by a single capacitor connected from the COM-
PENSATION pin to the OUT pin of the LM3460.
Applying a load pulse to the output of the regulator circuit
and observing the output voltage response is a good method
of verifying the stability of the control loop.
If excessive ringing on the output waveform is observed, this
usually indicates marginal stability resulting from insufficient
phase margin.
Test Circuit
The test circuit shown in Figure 3 can be used to measure
various LM3460 parameters. Test conditions are set by forc-
ing the appropriate voltage at the VOUT Set test point and se-
lecting the appropriate RL or IOUT as specified in the Electri-
cal Characteristics section. Use a DVM at the ″measure″ test
points to read the data.
VOUT Set Note: 0V to 500 mV for LM3460-1.5
0V to 200 mV for LM3460-1.2
FIGURE 3. Test Circuit
Setting the Output Voltage
If a regulated voltage is desired which is not available as a
standard voltage, the output voltage may be adjusted by us-
ing an external resistive divider (see Figure 4):
5
DS012603-9
www.national.com
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LM3460.PDF ] | |
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