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ADM7171 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADM7171
Beschreibung Fast Transient Response CMOS LDO
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 23 Seiten
ADM7171 Datasheet, Funktion
Data Sheet
6.5 V, 1 A, Ultralow Noise, High PSRR,
Fast Transient Response CMOS LDO
ADM7171
FEATURES
Input voltage range: 2.3 V to 6.5 V
Maximum load current: 1 A
Low noise: 5 μV rms independent of output voltage at
100 Hz to 100 kHz
Fast transient response: 1.5 μs for 1 mA to 500 mA load step
60 dB PSRR at 100 kHz
Low dropout voltage: 42 mV at 500 mA load, VOUT = 3 V
Initial accuracy: −0.5% (minimum), +1% (maximum)
Accuracy over line, load, and temperature: ±1.5%
Quiescent current, IGND = 0.7 mA with no load
Low shutdown current: 0.25 μA at VIN = 5 V
Stable with small 4.7 μF ceramic output capacitor
Adjustable and fixed output voltage options: 1.2 V to 5.0 V
Adjustable output from 1.2 V to VIN − VDO
Precision enable
Adjustable soft start
8-lead, 3 mm × 3 mm LFCSP package
Supported by ADIsimPower tool
APPLICATIONS
Regulation to noise sensitive applications: ADC and DAC
circuits, precision amplifiers, PLLs/VCOs, and clocking ICs
Communications and infrastructure
Medical and healthcare
Industrial and instrumentation
GENERAL DESCRIPTION
The ADM7171 is a CMOS, low dropout linear regulator (LDO)
that operates from 2.3 V to 6.5 V and provides up to 1 A of output
current. This high output current LDO is ideal for regulation of
high performance analog and mixed signal circuits operating
from 6 V down to 1.2 V rails. Using an advanced proprietary
architecture, the device provides high power supply rejection and
low noise, and achieves excellent line and load transient response
with just a small 4.7 μF ceramic output capacitor. Load transient
response is typically 1.5 μs for a 1 mA to 500 mA load step.
The ADM7171 is available in 17 fixed output voltage options.
The following voltages are available from stock: 1.3 V, 1.8 V,
2.5 V, 3.0 V, 3.3 V, 4.2 V, and 5.0 V. Additional voltages that are
available by special order are: 1.5 V, 1.85 V, 2.0 V, 2.2 V, 2.7 V,
2.75 V, 2.8 V, 2.85 V, 3.8 V, and 4.6 V. An adjustable version is
also available that allows output voltages that range from 1.2 V
to VIN − VDO with an external feedback divider.
Inrush current can be controlled by adjusting the start-up time
via the soft start pin. The typical start-up time with a 1 nF soft
start capacitor is 1.0 ms.
Rev. A
Document Feedback
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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
TYPICAL APPLICATION CIRCUIT
VIN = 5V
CIN
4.7µF
ON
OFF
ADM7171
VIN VOUT
VIN VOUT
SENSE
EN SS
GND
VOUT = 3.3V
COUT
4.7µF
CSS
1nF
Figure 1. ADM7171 with Fixed Output Voltage, 3.3 V
The ADM7171 regulator output noise is 5 μV rms independent
of the output voltage. The ADM7171 is available in an 8-lead,
3 mm × 3 mm LFCSP, making it not only a very compact solution,
but also providing excellent thermal performance for applications
requiring up to 1 A of output current in a small, low profile
footprint.
Figure 2. Transient Response (Trace 2), 1 mA to 500 mA Load Step in 400 ns (Trace 1)
Table 1. Related Devices
Device Input Voltage
ADM7170 2.3 V to 6.5 V
ADM7172 2.3 V to 6.5 V
Output Current
500 mA
2A
Package
8-lead LFCSP
8-lead LFCSP
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
©2014 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com






ADM7171 Datasheet, Funktion
ADM7171
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
VOUT 1
8 VIN
VOUT 2
SENSE 3
SS 4
ADM7171
TOP VIEW
(Not to Scale)
7 VIN
6 GND
5 EN
NOTES
1. THE EXPOSED PAD ENHANCES THERMAL PERFORMANCE
AND IS ELECTRICALLY CONNECTED TO GND INSIDE THE
PACKAGE. CONNECT THE EXPOSED PAD TO THE GROUND
PLANE ON THE BOARD TO ENSURE PROPER OPERATION.
Figure 3. Pin Configuration
Table 6. Pin Function Descriptions
Pin No.
Mnemonic
Description
1
VOUT
Regulated Output Voltage. Bypass this pin to GND with a 4.7 µF or greater capacitor.
2
VOUT
Regulated Output Voltage. This pin is internally connected to Pin 1.
3
SENSE
Sense Input. Connect this pin as close as possible to the load for best load regulation. Use an external
resistor divider to set the output voltage higher than the fixed output voltage.
4 SS Soft Start. A 1 nF external capacitor connected to SS results in a 1.0 ms start-up time.
5 EN Regulator Enable. Drive EN high to turn on the regulator; drive EN low to turn off the regulator. For
automatic startup, connect EN to VIN (Pin 7 or Pin 8).
6 GND Ground.
7 VIN Regulator Input Supply. Bypass this pin to GND with a 4.7 µF or greater capacitor.
8 VIN Regulator Input Supply. This pin is internally connected to Pin 7.
9 EP Exposed Pad. The exposed pad is on the bottom of the package. The exposed pad enhances thermal
performance and is electrically connected to GND inside the package. Connect the exposed pad to the
ground plane on the board to ensure proper operation.
Rev. A | Page 6 of 23

6 Page









ADM7171 pdf, datenblatt
ADM7171
0
ILOAD = 100mA
ILOAD = 200mA
ILOAD = 500mA
–20 ILOAD = 1A
–40
–60
–80
–100
1
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
Figure 34. Power Supply Rejection Ratio (PSRR) vs. Frequency, 300 mV
Headroom, VOUT = 3 V
0
–20
–40
–60
–80
–100
1
800mV
700mV
600mV
500mV
400mV
300mV
200mV
150mV
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
Figure 35. Power Supply Rejection Ratio (PSRR) vs. Frequency, VOUT = 5 V,
1 A Load Current, Various Headroom Voltages
0
–20
–40
–60
–80
–100
0
10Hz
100Hz
1kHz
10kHz
100kHz
1MHz
10MHz
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
HEADROOM (V)
Figure 36. Power Supply Rejection Ratio (PSRR) vs. Headroom, VOUT = 5 V,
1 A Load Current, Different Frequencies
Data Sheet
0
ILOAD = 100mA
ILOAD = 200mA
ILOAD = 500mA
–20 ILOAD = 1A
–40
–60
–80
–100
1
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
Figure 37. Power Supply Rejection Ratio (PSRR) vs. Frequency, 800 mV
Headroom, VOUT = 5 V
0
ILOAD = 100mA
ILOAD = 200mA
ILOAD = 500mA
–20 ILOAD = 1A
–40
–60
–80
–100
1
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
Figure 38. Power Supply Rejection Ratio (PSRR) vs. Frequency, 400 mV
Headroom, VOUT = 5 V
0
ILOAD = 100mA
ILOAD = 200mA
ILOAD = 500mA
–20 ILOAD = 1A
–40
–60
–80
–100
1
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
Figure 39. Power Supply Rejection Ratio (PSRR) vs. Frequency, 300 mV
Headroom, VOUT = 5 V
Rev. A | Page 12 of 23

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