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DC/DC Controller. ADP1864 Datasheet |
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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.
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ADP1864
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description ......................................................................... 1
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics ............................................. 6
Theory of Operation ........................................................................ 8
Loop Start-Up ............................................................................... 8
Short-Circuit Protection.............................................................. 9
Undervoltage Lockout (UVLO) ................................................. 9
Overvoltage Lockout Protection (OVP).................................... 9
Soft Start ........................................................................................ 9
REVISION HISTORY
10/05—Revision 0: Initial Version
Application Information................................................................ 10
Duty Cycle ................................................................................... 10
Ripple Current ............................................................................ 10
Sense Resistor.............................................................................. 10
Inductor Value ............................................................................ 10
MOSFET...................................................................................... 11
Diode............................................................................................ 11
Input Capacitor........................................................................... 11
Output Capacitor........................................................................ 11
Feedback Resistors ..................................................................... 12
Layout Considerations................................................................... 13
Example Applications Circuits ..................................................... 14
Outline Dimensions ....................................................................... 15
Ordering Guide .......................................................................... 15
Rev. 0 | Page 2 of 16
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ADP1864
SPECIFICATIONS
VIN = 5 V, TA = 25°C, unless otherwise noted.
Table 1.
Parameter
POWER SUPPLY
Input Voltage
Quiescent Current
Shutdown Supply Current
Undervoltage Lockout Threshold
Symbol
VIN
IQ
ISD
VUVLO
ERROR AMPLIFIER
FB Input Current
FB Input Current
IFB
IFB
Conditions
VIN = 3.15 V to 14 V, GATE = IN
VIN = 3.15 V to 14 V, COMP = GND
VIN falling, TA = −40°C to +85°C
VIN rising, TA = −40°C to +85°C
VFB = 0.8 V
VFB = 0.8 V, TA = −40°C to +85°C
Min Typ Max Unit
3.15 14 V
235 350 μA
7 15 μA
2.75 2.90 3.01 V
2.85 3.00 3.10 V
−20 -2
−35 -2
20 nA
35 nA
Amplifier Transconductance
COMP Startup Threshold
COMP Shutdown Threshold
COMP Startup Current Source
FB Regulation Voltage
Overvoltage Protection Threshold
Overvoltage Protection Hysteresis
CURRENT SENSE
Peak Current Sense Voltage
Peak Current Sense Voltage
Current Sense Gain
OUTPUT REGULATION
Line Regulation1
Load Regulation2
OSCILLATOR
Oscillator Frequency
FB Frequency Foldback Threshold
GATE DRIVE
Gate Rise Time
Gate Fall Time
Minimum On Time
SOFT START POWER-ON TIME
VOVP
VFB = 0.8 V, ICOMP = ±5 μA
VIN = 3.15 V to 14 V , TA = −40°C to +85°
VIN = 3.15 V to 14 V , TA = −40°C to +85°
COMP = GND
VIN = 3.15 V to 14 V , TA = −40°C to +85°
Measured at FB
TA = −40°C to +85°C
VIN = 3.15 V to 14 V, TA = −40°C to +85°C
VCS to VCOMP
VIN = 3.15 V to 14 V, VFB/VIN
VFB/VCOMP
VFB = 0.8 V
VFB = 0 V
CGATE = 3 nF
CGATE = 3 nF
PGATE minimum low duration
0.55
0.15
0.25
0.790
0.87
0.24
0.67
0.3
0.6
0.8
0.885
50
0.80
0.55
0.85
0.810
0.9
mS
V
V
μA
V
V
mV
90 125
80 125
12
mV
mV
V/V
0.12 mV/V
−2 mV/V
500 580 650 kHz
190 kHz
0.35 V
50 ns
40 ns
190 ns
1.1 ms
1 Line regulation is measured with the application circuit of Figure 1. Line regulation is specified as being the change in the FB voltage resulting from a 1 V change in the
IN voltage.
2 Load regulation is measured using the application circuit from Figure 1. Load regulation is specified as the change in the FB voltage resulting from a 1 V change in
COMP voltage. The COMP voltage range is typically 0.9 V to 2.3 V for the minimum to maximum load current condition.
Rev. 0 | Page 3 of 16
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