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ADP1864 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADP1864
Beschreibung Constant Frequency Current-Mode Step-Down DC/DC Controller
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 16 Seiten
ADP1864 Datasheet, Funktion
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Constant Frequency Current-Mode
Step-Down DC/DC Controller in TSOT
ADP1864
FEATURES
Wide input voltage range: 3.15 V to 14 V
Wide output voltage range: 0.8 V to input voltage
Pin-to-pin compatible with LTC1772, LTC3801
Up to 94% efficiency
0.8 V ±1.25% reference accuracy over temperature
Internal soft start
100% duty cycle for low dropout voltage
Current-mode operation for good line and load transient
response
7 μA shutdown current
235 μA quiescent supply current
Short-circuit and overvoltage protection
Small 6-lead TSOT package
APPLICATIONS
Wireless devices
1- to 3-cell Li-Ion battery-powered applications
Set-top boxes
Processor core power supplies
Hard disk drives
GENERAL DESCRIPTION
The ADP1864 is a compact, inexpensive, constant-frequency
current-mode step-down DC-to-DC controller. The ADP1864
drives a P-channel MOSFET that regulates an output voltage as
low as 0.8 V with ±2% accuracy, for up to 5 A load currents,
from input voltages as high as 14 V.
The ADP1864 provides system flexibility by allowing accurate
setting of the current limit with an external resistor, while the
output voltage is easily adjustable using two external resistors.
The ADP1864 includes an internal soft start to allow quick
power-up while preventing input inrush current. Additional
safety features include short-circuit protection, output over-
voltage protection, and input under voltage protection.
Current-mode control provides fast and stable load transient
performance, while the 580 kHz operating frequency allows a
small inductor to be used in the system. To further the life of a
battery source, the controller turns on the external P-channel
MOSFET 100% of the duty cycle in dropout.
The ADP1864 operates over the −40°C to +85°C temperature
range and is available in a small, low profile, 6-lead TSOT
package.
470pF
ADP1864
15kΩ
1 COMP
IN 5
2 GND
CS 4
80.6kΩ
3 FB
PGATE 6
174kΩ
0.03Ω
VIN = 3.3V to 10V
10μF
5μH 2.5V, 2.0A
47μF
Figure 1. Typical Applications Diagram
MOSFET = FDC638P
100
VOUT = 2.5V
95
90
85
3.3V
80
75
4.2V
70
65 5.0V
60
0.01
0.1 1.0
EFFICIENCY vs. LOAD CURRENT FOR APPLICATION
10.0
Figure 2. Efficiency vs. Load Current
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no 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. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2005 Analog Devices, Inc. All rights reserved.






ADP1864 Datasheet, Funktion
ADP1864
TYPICAL PERFORMANCE CHARACTERISTICS
0.81
VIN = 5V
0.805
0.80
0.795
0.79
–40 –20
0
20 40 60 80 100 120
TEMPERATURE (°C)
Figure 4. Reference Voltage vs. Temperature
600
VIN = 5V
590
580
570
560
550
–40 –20
0
20 40 60 80 100 120
TEMPERATURE (°C)
Figure 5. Normalized Oscillator Frequency vs. Temperature
3.1
3.05
3.0
2.95
UVLO RISE
2.9
2.85
UVLO FALL
2.8
2.75
2.7
–40 –20
0
20 40 60 80 100 120
TEMPERATURE (°C)
Figure 6. UVLO Voltage vs. Temperature (VIN Rising and VIN Falling)
0.8
0.7 COMP RISING
0.6
0.5
0.4
0.3 COMP FALLING
0.2
0.1
0
–40 –20
0
20 40 60 80 100 120
TEMPERATURE (°C)
Figure 7. COMP Shutdown Threshold vs. Temperature
2.52
2.50
2.48
2.46
2.44
2.42
2.40
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5
LOAD (A)
Figure 8. Typical Load Regulation (VIN = 5 V; See Figure 1)
2.52
2.515
2.51
2.505
2.50
3 5 7 9 11 13
VIN (V)
Figure 9. Typical Line Regulation vs. VIN (ILOAD = 1 A; See Figure 19)
Rev. 0 | Page 6 of 16

6 Page









ADP1864 pdf, datenblatt
ADP1864
FEEDBACK RESISTORS
The feedback resistor ratio sets the output voltage of the system.
ADP1864
3 FB
R2
R1
VOUT
Figure 15. Two Feedback Resistors Used to Set Output Voltage
0.8 V
= VOUT
×
R2
R1 + R2
( )R1 = R2 × VOUT 0.8
0.8
Choose 80.6 kΩ for R2. Using higher values for R2 results in
reduced output voltage accuracy while lower values cause
increased voltage divider current, increasing quiescent current
consumption.
Rev. 0 | Page 12 of 16

12 Page





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