ANALOG DEVICES ADP1864 Service Manual

Constant Frequency Current-Mode

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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 supply 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

Step-Down DC-to-DC Controller in TSOT

ADP1864

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 ±1.25% 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, and 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 overvoltage
protection, and input undervoltage 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 during dropout.

The ADP1864 operates over the −40°C to +125°C temperature
range and is available in a small, low profile, 6-lead TSOT package.

TYPICAL APPLICATIONS DIAGRAM

25kΩ

470pF

68pF

80.6kΩ

174kΩ

1

2

3

COMP

ADP1864

GND

FB

PGATE

CS

6

5

IN

4

Figure 1.

0.03Ω

= 3.15V TO 14V

V

IN

10µF

5µH

2.5V, 2.0A

47µF

05562-001

Rev. B

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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
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Tel: [phone] www.analog.com
Fax: [phone] ©2005–2008 Analog Devices, Inc. All rights reserved.

ADP1864

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TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1

General Description ......................................................................... 1

Typical Applications Diagram ........................................................ 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

Absolute Maximum Ratings ............................................................ 4

ESD Caution .................................................................................. 4

Pin Configuration and Function Descriptions ............................. 5

Typical Performance Characteristics ............................................. 6

Theory of Operation ........................................................................ 8

Loop Startup .................................................................................. 8

Short-Circuit Protection .............................................................. 9

Undervoltage Lockout (UVLO) ................................................. 9

Overvoltage Lockout Protection (OVP).................................... 9

Soft Start .........................................................................................9

Applications 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 ..................................................................... 11

Layout Considerations ................................................................... 12

Example Applications Circuits ..................................................... 13

Outline Dimensions ....................................................................... 14

Ordering Guide .......................................................................... 14

REVISION HISTORY

4/08—Rev. A to Rev. B

Change General Description Section ............................................. 1

Deleted Figure 2 ................................................................................ 1

Change to FB Regulation Voltage Parameter ................................ 3

Change to MOSFET Section ......................................................... 11

Changes to Ordering Guide .......................................................... 14

2/07—Rev 0. to Rev. A

Updated Format .................................................................. Universal

Changes to Figure 1 .......................................................................... 1

Changes to General Description .................................................... 2

Changes to Specifications ................................................................ 3

Change to Figure 13 ......................................................................... 8

Replaced Layout Considerations Section .................................... 12

Replaced Example Applications Circuits Section ...................... 13

10/05—Revision 0: Initial Version

Rev. B | Page 2 of 16

ADP1864

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SPECIFICATIONS

VIN = 5 V, TJ = 25°C, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

POWER SUPPLY

Input Voltage VIN 3.15 14 V

Quiescent Current IQ V

Shutdown Supply Current ISD V

Undervoltage Lockout Threshold V

V

UVLO

V
ERROR AMPLIFIER

FB Input Current IFB V

V

Amplifier Transconductance VFB = 0.8 V, I

COMP Startup Threshold VIN = 3.15 V to 14 V, TJ = −40°C to +125°C 0.55 0.67 0.80 V

COMP Shutdown Threshold VIN = 3.15 V to 14 V, TJ = −40°C to +125°C 0.15 0.3 0.55 V

COMP Start-Up Current Source COMP = GND 0.25 0.6 0.95 μA

FB Regulation Voltage VIN = 3.15 V to 14 V, TJ = −40°C to +125°C 0.790 0.8 0.810 V

Overvoltage Protection Threshold V

Measured at FB, TJ = −40°C to +125°C 0.87 0.885 0.9 V

OVP

Overvoltage Protection Hysteresis 50 mV

CURRENT SENSE

Peak Current Sense Voltage TJ = −40°C to +125°C 90 125 mV

V

Current Sense Gain VCS to V

OUTPUT REGULATION

Line Regulation

Load Regulation

1

V

2

V

OSCILLATOR

Oscillator Frequency VFB = 0.8 V, TJ = −40°C to +125°C 500 580 650 kHz

V

FB Frequency Foldback Threshold 0.35 V

GATE DRIVE

Gate Rise Time C

Gate Fall Time C

Minimum On Time PGATE minimum low duration 190 ns

SOFT START POWER-ON TIME 1.1 ms

1

Line regulation is measured using the application circuit in . Line regulation is specified as 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 in . Load regulation is specified as the change in the FB voltage resulting from a 1 V change in the

COMP voltage. The COMP voltage range is typically 0.9 V to 2.3 V for the minimum to maximum load current condition.

= 3.15 V to 14 V, PGATE = IN 235 360 μA

IN

= 3.15 V to 14 V, COMP = GND 7 15 μA

IN

falling, TJ = −40°C to +125°C 2.75 2.90 3.01 V

IN

rising, TJ = −40°C to +125°C 2.85 3.00 3.15 V

IN

= 0.8 V, TJ = 25°C −20 −2 +20 nA

FB

= 0.8 V, TJ = −40°C to +125°C −40 −2 +40 nA

FB

= ±5 μA 0.24 mmho

COMP

= 3.15 V to 14 V, TJ = −40°C to +125°C 70 125 mV

IN

12 V/V

COMP

= 3.15 V to 14 V, VFB/VIN 0.12 mV/V

IN

−2 mV/V

FB/VCOMP

= 0 V 190 kHz

FB

= 3 nF 50 ns

GATE

= 3 nF 40 ns

GATE

Figure 1

Figure 1

Rev. B | Page 3 of 16

ADP1864

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ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

IN to GND −0.3 V to +16 V
CS, PGATE to GND −0.3 V to (VIN + 0.3 V)
FB, COMP to GND −0.3 V to +6 V
θJA 2-Layer (SEMI Standard Board) 315°C/W
θJA 4-Layer (JEDEC Standard Board) 186°C/W
Operating Junction Temperature Range −40°C to +125°C
Storage Temperature Range −65°C to +150°C
Lead Temperature

Rework Temperature (J-STD-020B) 260°C
Peak Reflow Temperature,

(20 sec to 40 sec, J-STD-020B)

260°C

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

ESD CAUTION

Rev. B | Page 4 of 16

ADP1864

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PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

PGATE

6

5

IN

4

CS

05562-003

Table 3. Pin Function Descriptions

Pin No. Mnemonic Description

1 COMP

Regulator Compensation Node. COMP is the output of the internal transconductance error amplifier. Connect a
series RC from COMP to GND to compensate for the control loop. Add an extra high frequency capacitor between
COMP and GND to further reduce switching jitter. The value of this is typically one-tenth of the main compensation
capacitor. Pulling the COMP pin below 0.3 V disables the ADP1864 and turns off the external PFET.

2 GND

Analog Ground. Directly connect the compensation and feedback networks to GND, preferably with a small analog
GND plane. Connect GND to the power ground (PGND) plane with a narrow track at a single point close to the GND
pin. See the Layout Considerations section for more information.

3 FB

Feedback Input. Connect a resistive voltage divider from the output voltage to FB to set the output voltage. The
regulation feedback voltage is 0.8 V. Place the feedback resistors as close as possible to the FB pin.

4 CS

Current Sense Input. CS is the negative input of the current sense amplifier. It provides the current feedback signal
used to terminate the PWM on time. Place a current sense resistor between IN and CS to set the current limit. The
current limit threshold is typically 125 mV.

5 IN

Power Input. IN is the power supply to the ADP1864 and the positive input of the current sense amplifier. Connect
IN to the positive side of the input voltage source. Bypass IN to PGND with a 10 μF or larger capacitor as close as possible
to the ADP1864. For additional high frequency noise reduction, add a 0.1 μF capacitor to PGND at the IN pin.

6 PGATE

Gate Drive Output. PGATE drives the gate of the external P-channel MOSFET. Connect PGATE to the gate of the
external MOSFET.

COMP

1

ADP1864

2

GND

TOP VIEW

(Not to Scale)

3

FB

Figure 2. Pin Configuration

Rev. B | Page 5 of 16