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Advanced

AMS1505V

Monolithic

5A ULTRA LOW DROPOUT VOLTAGE REGULATORS

Systems

FEATURES

APPLICATIONS

·
·

Adjustable or Fixed Output

·
·

High Speed Video/Graphic Cards

1.5V, 2.5V, 2.85V, 3.0V, 3.3V, 3.5V and 5.0V

·
·

Post Regulators for Switching Supplies

·
·

Output Current of 5A

·
·

Microprocessor Supply

·
·

Low Dropout, 350mV max. at 5A Output Current

·
·

Adjustable Power Supply

·
·

Fast Transient Response

·
·

Notebook/Personal Computer Supplies

·
·

Remote Sense

·
·

High Current Regulators

GENERAL DESCRIPTION

The

Designed specially for video applications where a very low dropout is critical, the AMS1505V series of adjustable and fixed
low dropout voltage regulators provide 5A output current to power the new generation of high speed video cards. The dropout
voltage of the device is 200mV max. at 3A loads and rising to 350mV at maximum output current. A second low current
input voltage 1V or greater then the output voltage is required to achieve this dropout.
New features have been added to the AMS1505V: a remote Sense pin is brought out virtually eliminating output voltage
variations due to load changes. The typical load regulation, measured at the Sense pin, for a load current step of 100mA to 5A
is less than 1mV. The AMS1505V series has fast transient response. To further improve the transient response the addition of
a small capacitor on the Adjust pin is recommended.
The AMS1505V series are ideal for generating supplies of 2V to 3V on boards where both 5V and 3.3V supplies are
available.

The AMS1505V devices are offered in 5 lead TO-220 and TO-263 (plastic DD) packages.

ORDERING INFORMATION:

PIN CONNECTIONS

PACKAGE TYPE

OPERATING

5 LEAD TO-263

5 LEAD TO-220

TEMPERATURE RANGE

AMS1505CMV

AMS1505CTV

0 to 125

AMS1505CMV-1.5 AMS1505CTV-1.5

0 to 125

AMS1505CMV-2.5 AMS1505CTV-2.5

0 to 125

AMS1505CMV-2.85 AMS1505CTV-2.85

0 to 125

AMS1505CMV-3.0 AMS1505CTV-3.0

0 to 125

AMS1505CMV-3.3 AMS1505CTV-3.3

0 to 125

AMS1505CMV-3.5 AMS1505CTV-3.5

0 to 125

AMS1505CMV-5.0 AMS1505CTV-5.0

0 to 125

5
4
3
2
1

Vpower
Vcontrol
OUTPUT

ADJUST/GND
SENSE

FRONT VIEW

5 LEAD TO-263

5
4
3
2
1

POWER

CONTROL

OUTPUT

ADJUST/GND

SENSE

FRONT VIEW

5 LEAD TO-220

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AMS1505V

ABSOLUTE MAXIMUM RATINGS

(Note 1)

POWER

Input Voltage

Soldering information

CONTROL

Input Voltage

13V

Lead Temperature (10 sec)

300

Operating Junction Temperature Range

Thermal Resistance

Control Section

C to 125

TO-220 package

= 50

C/W

Power Transistor

C to 150

TO-263 package

= 30

C/W*

Storage temperature

- 65

C to +150

* With package soldering to 0.5in

copper area over backside ground

plane or internal power plane

can vary from 20

C/W to

C/W

depending on mounting technique.

ELECTRICAL CHARACTERISTICS

Electrical Characteristics at I

LOAD

= 0 mA, and T

= +25°C unless otherwise specified.

Parameter

Device

Conditions

Min Typ Max

Units

Reference Voltage

AMS1505V

CONTROL

= 2.75V, V

POWER

=2V, I

LOAD

= 10mA

CONTROL

= 2.7V to 12V, V

POWER

=3.3V to 5.5V,

LOAD

= 10mA to 5A

1.238

1.250

1.262

Output Voltage

AMS1505V-1.5

CONTROL

= 4V, V

POWER

=2.V, I

LOAD

= 0mA

CONTROL

= 3V, V

POWER

=2.3V, I

LOAD

= 0mA to 5A

1.485

1.500

1.515

AMS1505V-2.5

CONTROL

= 5V, V

POWER

=3.3V, I

LOAD

= 0mA

CONTROL

= 4V, V

POWER

=3.3V, I

LOAD

= 0mA to 5A

2.475

2.500

2.525

AMS1505V-2.85

CONTROL

= 5.35V, V

POWER

=3.35V, I

LOAD

= 0mA

CONTROL

= 4.4V, V

POWER

=3.7V, I

LOAD

= 0mA to 5A

2.833

2.850

2.867

AMS1505V-3.0

CONTROL

= 5.5V, V

POWER

=3.5V, I

LOAD

= 0mA

CONTROL

= 4.5V, V

POWER

=3.8V, I

LOAD

= 0mA to 5A

2.970

3.000

3.030

AMS1505V-3.3

CONTROL

= 5.8V, V

POWER

=3.8V, I

LOAD

= 0mA

CONTROL

= 4.8V, V

POWER

=4.1V, I

LOAD

= 0mA to 5A

3.235

3.300

3.333

AMS1505V-3.5

CONTROL

= 6V, V

POWER

=4V, I

LOAD

= 0mA

CONTROL

= 5V, V

POWER

=4.3V, I

LOAD

= 0mA to 5A

3.430

3.500

3.535

AMS1505V-5.0

CONTROL

= 7.5V, V

POWER

=5.5V, I

LOAD

= 0mA

CONTROL

= 6.5V, V

POWER

=5.8V, I

LOAD

= 0mA to 5A

4.950

5.000

5.030

Line Regulation

AMS1505V/-1.5/-2.5/

-2.85/-3.0/-3.3/-3.5/-5.0

LOAD

= 10 mA , 1.5V

CONTROL

- V

OUT

)

12V

0.8V

POWER

- V

OUT

)

5.5V

Load Regulation

AMS1505V/-1.5/-2.5/

-2.85/-3.0/-3.3/-3.5/-5.0

CONTROL

= V

OUT

+ 2.5V, V

POWER

OUT

+ 0.8V,

LOAD

= 10mA to 5A

Minimum Load
Current

AMS1505V

CONTROL

= 5V, V

POWER

=3.3V, V

ADJ

= 0V (Note 3)

Control Pin Current

(Note 4)

AMS1505V/-1.5/-2.5/

-2.85/-3.0/-3.3/-3.5/-5.0

CONTROL

= V

OUT

+ 2.5V, V

POWER

OUT

+ 0.8V,

LOAD

= 10mA to 5A

Ground Pin Current

(Note 4)

AMS1505V/-1.5/-2.5/

-2.85/-3.0/-3.3/-3.5/-5.0

CONTROL

= V

OUT

+ 2.5V, V

POWER

OUT

+ 0.8V,

LOAD

= 10mA to 5A

Adjust Pin Current

AMS1505V

CONTROL

= 2.75V, V

POWER

= 2.05V, I

LOAD

= 10mA

120

Ripple Rejection

AMS1505V/-1.5/-2.5/

-2.85/-3.0/-3.3/-3.5/-5.0

CONTROL

= V

POWER

= V

OUT

+ 2.5V, V

RIPPLE

= 1V

P-P

LOAD

= 2A

Thermal Regulation

AMS1505V

= 25°C, 30ms pulse

0.002

0.020

Thermal Resistance
Junction-to-Case

T Package: Control Circuitry/ Power Transistor

M Package: Control Circuitry/ Power Transistor

0.65/2.70

°C/W

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AMS1505V

ELECTRICAL CHARACTERISTICS

Electrical Characteristics at I

OUT

= 0 mA, and T

= +25°C unless otherwise specified.

Parameter

Device

Conditions

Min Typ Max

Units

Dropout Voltage

Note 2

Control Dropout
(V

CONTROL

- V

OUT

)

AMS1505V/-1.5/-2.5/

-2.85/-3.0/-3.3/-3.5/-5.0

POWER

OUT

+ 0.8V, I

LOAD

= 10mA

POWER

OUT

+ 0.8V, I

LOAD

= 5A

1.00

1.15

1.20

1.30

Power Dropout
(V

POWER

- V

OUT

)

AMS1505V/-1.5/-2.5/

-2.85/-3.0/-3.3/-3.5/-5.0

CONTROL

OUT

+ 2.5V, I

LOAD

= 3A

CONTROL

OUT

+ 2.5V, I

LOAD

= 5A

175

300

200

350

Parameters identified with boldface type apply over the full operating temperature range.

Note 1:

Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. For guaranteed specifications and test conditions, see the

Electrical Characteristics

The guaranteed specifications apply only for the test conditions listed.

Note 2:

Unless otherwise specified V

OUT

= V

SENSE

. For the adjustable device V

ADJ

= 0V.

Note 3:

The dropout voltage for the AMS1505V is caused by either minimum control voltage or minimum power voltage. The specifications represent the

minimum input/output voltage required to maintain within 1% regulation.

Note 4:

For the adjustable device the minimum load current is the minimum current required to maintain regulation. Normally the current in the resistor divider

used to set the output voltage is selected to meet the minimum load current requirement.

Note 5:

The control pin current is the drive current required for the output transistor. This current will track output current with a ratio of about 1:100. The

minimum value is equal to the quiescent current of the device.

PIN FUNCTIONS

Sense (Pin 1): This pin is the positive side of the
reference voltage for the device. With this pin it is
possible to Kelvin sense the output voltage at the load.

Adjust/Ground (Pin 2): This pin is the negative side of
the reference voltage for the device. Adding a small
bypass capacitor from the Adjust pin to ground improves
the transient response.

Output (Pin 3): This is the power output of the device.

CONTROL

(Pin 4): This pin is the supply pin for the

control circuitry of the device. The current flow into
this pin will be about 1% of the output current. The
voltage at this pin must be 1.3V or greater than the
output voltage for the device to regulate.

V

POWER

(Pin 5): This pin is the collector to the power

device of the AMS1505V. The output load current is
supplied through this pin. The voltage at this pin must
be between 0.1V and 0.35V greater than the output
voltage for the device to regulate.

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AMS1505V

APPLICATION HINTS

The AMS1505V series of adjustable and fixed regulators are
designed to power the new generation of microprocessors. The
AMS1505V is designed to make use of multiple power supplies,
existing in most systems, to reduce the dropout voltage. One of
the advantages of the two supply approach is maximizing the
efficiency.
The second supply is at least 0.35V greater than output voltage
and is providing the power for the control circuitry and supplies
the drive current to the NPN output transistor. This allows the
NPN to be driven into saturation; thereby reducing the dropout
voltage by a VBE compared to conventional designs. For the
control voltage the current requirement is small equal to about
1% of the output current or approximately 50mA for a 5A load.
Most of this current is drive current for the NPN output transistor.
This drive current becomes part of the output current. The
maximum voltage on the Control pin is 13V. The maximum
voltage at the Power pin is 7V. Ground pin current for fixed
voltage devices is typical 6mA and is constant as a function of
load. Adjust pin current for adjustable devices is 60

A at 25

and varies proportional to absolute temperature.
The improved frequency compensation of AMS1505V permits the
use of capacitors with very low ESR. This is critical in addressing
the needs of modern, low voltage high sped microprocessors. The
new generation of microprocessors cycle load current from several
hundred mA to several A in tens of nanoseconds. Output voltage
tolerances are tighter and include transient response as part of the
specification. Designed to meet the fast current load step
requirements of the video-processors, the AMS1505V also saves
total cost by needing less output capacitance to maintain
regulation.
Careful design of the AMS1505V has eliminated any supply
sequencing issues associated with a dual supply system. The
output voltage will not turn on until both supplies are operating.
If the control voltage comes up first, the output current will be
limited to a few milliamperes until the power input voltage comes
up. If power input comes up first the output will not turn on at all
until the control voltage comes up. The output can never come up
unregulated.
The new features of the AMS1505V require additional pins over
the traditional 3-terminal regulator. Both the fixed and adjustable
versions have remote sense pins, permitting very accurate
regulation of output voltage at the load, rather than at the
regulator. As a result, over an output current range of 100mA to
5A with a 2.5V output, the typical load regulation is less than
1mV. Optimum transient response is provided using a capacitor
in the range of 0.1

F to 1

F for bypassing the Adjust pin. The

value chosen will depend on the amount of output capacitance in
the system.
In addition to the enhancements mentioned, the reference
accuracy has been improved by a factor of two with a guaranteed
initial tolerance of

1% at 25

C. This device can hold 1%

accuracy over the full temperature range and load current range,
guaranteed, when combined with ratiometrically accurate internal
divider resistors and operating with an input/output differential of
well under 1V.

Typical applications for the AMS1505V include 3.3V to 2.9V
conversion with a 5V control supply, 5V to 4.7V conversion with
a 12V control supply or 5V to 3.6V conversion with a 12V
control supply. Capable of 5A of output current with a maximum
dropout of 350mV the AMS1505V also has a fast transient
response that allows it to handle large current changes associated
with the new generation of video-processors. The device is fully
protected against overcurrent and overtemperature conditions.

Grounding and Output Sensing

The AMS1505V allows true Kelvin sensing for both the high and
low side of the load. As a result the voltage regulation at he load
can be easily optimized. Voltage drops due to parasitic
resistances between the regulator and the load can be placed
inside the regulation loop of the AMS1505V. The advantages of
remote sensing are illustrated in figures 1 through 3.
Figure 1 shows the device connected as a conventional 3 terminal
regulator with the Sense lead connected directly to the output of
the device. R

is the parasitic resistance of the connections

between the device and the load. Typically the load is a
microprocessor and R

is made up of the PC traces and /or

connector resistances (in the case of a modular regulator)
between the regulator and the processor. Trace A of figure 3
illustrates the effect of RP. Very small resistances cause
significant load regulation steps.
Figure 2 shows the device connected to take advantage of the
remote sense feature. The Sense pin and the top of the resistor
divider are connected to the top of the load; the bottom of the
resistor divider is connected to the bottom of the load. R

is now

connected inside the regulation loop of the AMS1505V and for
reasonable values of R

the load regulation at the load will be

negligible. The effect on output regulation can be seen in trace B
of figure 3.

CONTROL

POWER
SENSE

AMS1505V

OUTPUT

ADJ

LOAD

OUT

3.3V

Figure 1. Conventional Load Sensing

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AMS1505V

APPLICATION HINTS

CONTROL

POWER
SENSE

AMS1505V

OUTPUT

ADJ

LOAD

OUT

3.3V

Figure 2. Remote Load Sensing

(

OUT

)(R

)

TIME

OUT

FIGURE 1

OUT

FIGURE 2

OUT

Figure 3. Remote Sensing Improves Load Regulation

Voltage drops due to R

are not eliminated; they will add to the

dropout voltage of the regulator regardless of whether they are
inside or outside the regulation loop. The AMS1505V can control
the voltage at the load as long as the input-output voltage is
greater than the total of the dropout voltage of the device plus the
voltage drop across R

Stability

The circuit design used in the AMS1505V series requires the use
of an output capacitor as part of the device frequency
compensation. The addition of

150

F aluminum electrolytic or a

F solid tantalum on the output will ensure stability for all

operating conditions. For best frequency response use capacitors
with an ESR of less than 1

In order to meet the transient requirements of the processor larger
value capacitors are needed. Tight voltage tolerances are required
in the power supply. To limit the high frequency noise generated
by the processor high quality bypass capacitors must be used. In
order to limit parasitic inductance (ESL) and resistance (ESR) in
the capacitors to acceptable limits, multiple small ceramic
capacitors in addition to high quality solid tantalum capacitors are
required.
When the adjustment terminal is bypassed to improve the ripple
rejection, the requirement for an output capacitor increases. The
Adjust pin is brought out on the fixed voltage device specifically

to allow this capability. To ensure good transient response with
heavy load current changes capacitor values on the order of
100

F are used in the output of many regulators. To further

improve stability and transient response of these devices larger
values of output capacitor can be used.
The modern processors generate large high frequency current
transients. The load current step contains higher order frequency
components than the output coupling network must handle until
the regulator throttles to the load current level. Because they
contain parasitic resistance and inductance, capacitors are not
ideal elements. These parasitic elements dominate the change in
output voltage at the beginning of a transient load step change.
The ESR of the output capacitors produces an instantaneous step
in output voltage (

I)(ESR). The ESL of the output

capacitors produces a droop proportional to the rate of change of
the output current (V= L)(

t). The output capacitance

produces a change in output voltage proportional to the time until
the regulator can respond (

t) (

I/C). Figure 4 illustrates

these transient effects.

CAPACITANCE
EFFECTS

ESR
EFFECTS

ESL
EFFECTS

POINT AT WHICH REGULATOR

TAKES CONTROL

SLOPE, V/t =

I/C

Figure 4.

Output Voltage

The AMS1505V series develops a 1.25V reference voltage
between the Sense pin and the Adjust pin (Figure5). Placing a
resistor between these two terminals causes a constant current to
flow through R1 and down through R2 to set the overall output
voltage. In general R1 is chosen so that this current is the
specified minimum load current of 10mA.The current out of the
Adjust pin is small, typically 50

A and it adds to the current

from R1. Because I

ADJ

is very small it needs to be considered

only when very precise output voltage setting is required. For
best regulation the top of the resistor divider should be connected
directly to the Sense pin.

CONTROL

POWER
OUTPUT

AMS1505V

SENSE

ADJ

OUT

REF

POWER

ADJ

CONTROL

OUT

= V

REF

(

1+ R2/R1)+I

ADJ

Figure 5. Setting Output Voltage

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AMS1505V

APPLICATION HINTS

Protection Diodes

Unlike older regulators, the AMS1505V family does not need any
protection diodes between the adjustment pin and the output and
from the output to the input to prevent die over-stress. Internal
resistors are limiting the internal current paths on the AMS1505V
adjustment pin, therefore even with bypass capacitors on the
adjust pin no protection diode is needed to ensure device safety
under short-circuit conditions. The Adjust pin can be driven on a
transient basis

7V with respect to the output without any device

degradation.
Diodes between the Output pin and V

POWER

pin are not usually

needed. Microsecond surge currents of 50A to 100A can be
handled by the internal diode between the Output pin and V

POWER

pin of the device. In normal operations it is difficult to get those
values of surge currents even with the use of large output
capacitances. If high value output capacitors are used, such as
1000

F to 5000

F and the V

POWER

pin is instantaneously shorted

to ground, damage can occur. A diode from output to input is
recommended, when a crowbar circuit at the input of the
AMS1505V is used (Figure 6). Normal power supply cycling or
even plugging and unplugging in the system will not generate
current large enough to do any damage.

CONTROL

POWER
OUTPUT

AMS1505V

SENSE

ADJ

OUT

POWER

D2*

D1*

CONTROL

Figure 6. Optional Clamp Diodes Protect Against

Input Crowbar Circuits

If the AMS1505V is connected as a single supply device with the
control and power input pins shorted together the internal diode
between the output and the power input pin will protect the
control input pin. As with any IC regulator, none the protection
circuitry will be functional and the internal transistors will break
down if the maximum input to output voltage differential is
exceeded.

Thermal Considerations

The AMS1505V series have internal power and thermal limiting
circuitry designed to protect the device under overload conditions.
However maximum junction temperature ratings should not be
exceeded under continuous normal load conditions. Careful
consideration must be given to all sources of thermal resistance
from junction to ambient, including junction-to-case, case-to-heat
sink interface and heat sink resistance itself.

Thermal resistance specification for both the Control Section and
the Power Transistor are given in the electrical characteristics.
The thermal resistance of the Control section is given as
0.65

C/W and junction temperature of the Control section can

run up to 125

C. The thermal resistance of the Power section is

given as 2.7

C/W and junction temperature of the Power section

can run up to 150

C. Due to the thermal gradients between the

power transistor and the control circuitry there is a significant
difference in thermal resistance between the Control and Power
sections.
Virtually all the power dissipated by the device is dissipated in
the power transistor. The temperature rise in the power transistor
will be greater than the temperature rise in the Control section
making the thermal resistance lower in the Control section. At
power levels below 12W the temperature gradient will be less
than 25

C and the maximum ambient temperature will be

determined by the junction temperature of the Control section.
This is due to the lower maximum junction temperature in the
Control section. At power levels above 12W the temperature
gradient will be greater than 25

C and the maximum ambient

temperature will be determined by the Power section. In both
cases the junction temperature is determined by the total power
dissipated in the device. For most low dropout applications the
power dissipation will be less than 12W.
The power in the device is made up of two components: the
power in the output transistor and the power in the drive circuit.
The power in the control circuit is negligible.
The power in the drive circuit is equal to:

DRIVE

= (V

CONTROL

- V

OUT

)(I

CONTROL

)

where I

CONTROL

is equal to between I

OUT

/100(typ) and

OUT

/58(max).

The power in the output transistor is equal to:

OUTPUT

= (V

POWER

-V

OUT

)(I

OUT

)

The total power is equal to:

TOTAL

= P

DRIVE

+ P

OUTPUT

Junction-to-case thermal resistance is specified from the IC
junction to the bottom of the case directly below the die. This is
the lowest resistance path for the heat flow. In order to ensure the
best possible thermal flow from this area of the package to the
heat sink proper mounting is required. Thermal compound at the
case-to-heat sink interface is recommended. A thermally
conductive spacer can be used, if the case of the device must be
electrically isolated, but its added contribution to thermal
resistance has to be considered.

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ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: AMS1505V-2.85