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PDF DS2501 Data sheet ( Hoja de datos )
| Número de pieza | DS2501 | |
| Descripción | 1A VERY LOW DROPOUT VOLTAGE REGULATORS | |
| Fabricantes | Advanced Monolithic Systems | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de DS2501 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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Advanced
Monolithic
Systems
AMS2501/AMS2502
1A VERY LOW DROPOUT VOLTAGE REGULATORS
FEATURES
• Adjustable or Fixed Output
1.5V, 1.8V, 2.5V, 2.85V, 3.0V, 3.3V, 3.5V and 5.0V
• Output Current of 1A
• Low Dropout, typ. 200mV at 500mA Output Current
• Fast Transient Response
• Remote Sense
APPLICATIONS
• High Efficiency Current Regulators
• Post Regulators for Switching Supplies
• Audio/Video/Modem Card Supply
• Adjustable Power Supply
• Notebook/Personal Computer Supplies
GENERAL DESCRIPTION
TThhee AMS2501/AMS2502 series of adjustable and fixed low dropout voltage regulators are designed to provide 1A output
current. The dropout voltage of the device is 100mV at light loads and rising to 200mV at 500mA output current. A second
input voltage of 1.2V or greater than the output is required to achieve this dropout. The AMS2501/AMS2502 can also be used
as a single supply device by connecting pin1 and pin 8 together. In this case the dropout voltage will be typically 1.2V.
New features have been added to the AMS2501: a remote Sense pin is brought out virtually eliminating output voltage
variations due to load changes. AMS2502 has an additional feature of an On/Off pin to keep the device in stand-by mode.
The typical load regulation, measured at the Sense pin, for a load current step of 100mA to 1A is less than 1mV.
The AMS2501/AMS2502 series has fast transient response. On the AMS2502 the reference voltage is brought out to allow
the user to add a bypass capacitor for lower noise and transient response improvement.
The AMS2501/AMS2502 series are ideal for generating supplies of 1.25V to 3V where both 5V and 3.3V supplies are
available.
The AMS2501/AMS2502 devices are offered in 8 lead SOIC package.
ORDERING INFORMATION:
PACKAGE TYPE
8 LEAD SO-8
AMS2501CS
AMS2501CS-1.5
AMS2501CS-1.8
AMS2501CS-2.5
AMS2501CS-2.85
AMS2501CS-3.0
AMS2501CS-3.3
AMS2501CS-3.5
AMS2501CS-5.0
AMS2502CS
AMS2502CS-1.5
AMS2502CS-1.8
AMS2502CS-2.5
AMS2502CS-2.85
AMS2502CS-3.0
AMS2502CS-3.3
AMS2502CS-3.5
AMS2502CS-5.0
OPERATING JUNCTION
TEMPERATURE RANGE
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
0 to 125° C
PIN CONNECTIONS
AMS2501 8L SOIC
POWER IN 1
OUTPUT 2
OUTPUT 3
SENSE 4
8 CONTROL IN
7 N/C
6 ADJ/GND
5 N/C
Top View
AMS2502 8L SOIC
POWER IN 1
OUTPUT 2
OUTPUT 3
SENSE 4
8 CONTROL IN
7 BYPASS
6 ADJ/GND
5 ON/OFF
Top View
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723
1 page  
APPLICATION HINTS
5V
3.3V
CONTROL
POWER SENSE
AMS2501
OUTPUT
ADJ
R1
R2
RP
LOAD
RP
+
VOUT
-
Figure 2. Remote Load Sensing
VOUT
FIGURE 1
VOUT
FIGURE 2
(∆IOUT)(RP)
IOUT
TIME
Figure 3. Remote Sensing Improves Load Regulation
Voltage drops due to RP 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 AMS2501/AMS2502
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 RP.
Stability
The circuit design used in the AMS2501/AMS2502 series
requires the use of an output capacitor as part of the device
frequency compensation. The addition of 150µF aluminum
electrolytic or a 22µF solid tantalum on the output will ensure
stability for all operating conditions. For best frequency response
use capacitors with an ESR of less than 1Ω.
In order to increase the transient response larger value capacitors
are needed. To limit the high frequency noise generated by the
load 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
reference voltage is brought out specifically to allow this
capability.
AMS2501/AMS2502
Some of the loads 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 (∆V=∆I)(ESR). The ESL of the output
capacitors produces a droop proportional to the rate of change of
the output current (V= L)(∆I/∆t). The output capacitance
produces a change in output voltage proportional to the time until
the regulator can respond (∆V=∆t) (∆I/C). Figure 4 illustrates
these transient effects.
ESR
EFFECTS
ESL
EFFECTS
CAPACITANCE
EFFECTS
SLOPE, V/t = ∆I/C
POINT AT WHICH REGULATOR
TAKES CONTROL
Figure 4.
Output Voltage
The AMS2501/AMS2502 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 40µA and it adds to the
current from R1. Because IADJ 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.
VCONTROL
+
VPOWER
+
CONTROL
POWER OUTPUT
AMS2501
SENSE
ADJ
IADJ
50µA
VREF
VOUT = VREF (1+ R2/R1)+IADJR2
+
R1
R2
Figure 5. Setting Output Voltage
VOUT
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet DS2501.PDF ] | |
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