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Low Profile, 500 mA, 6 MHz, Synchronous,

Step-Down, DC-to-DC Converter

ADP2125

Rev. A

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FEATURES

1.26 V fixed output voltage

Clock signal enable

6 MHz (maximum) operating frequency

500 mA continuous output current

Input voltage: 2.1 V to 5.5 V

0.3 µA (typical) shutdown supply current

Compatible with tiny multilayer inductors

Internal synchronous rectifier

Internal compensation

Internal soft start

Output-to-ground short-circuit protection

Current-limit protection

Undervoltage lockout

Thermal shutdown protection

Ultrasmall, 0.405 mm height (maximum), 6-ball BUMPED_CHIP

APPLICATIONS

Mobile phones

Digital still/video cameras

Digital audio

Portable equipment

Camera modules

Image stabilization systems

GENERAL DESCRIPTION

The ADP2125 is a high frequency, step-down, dc-to-dc

converter optimized for portable applications in which board

area and battery life are critical constraints. Fixed frequency

operation at 6 MHz enables the use of tiny ceramic inductors

and capacitors. Additionally, the synchronous rectification

improves efficiency and results in fewer external components.

Over all load currents, the device uses a voltage regulating

pulse-width modulation (PWM) mode that maintains a

constant frequency with excellent stability and transient

response. The ADP2125 is enabled by a 6 MHz to 27 MHz

external clock signal applied to the EXTCLK pin. When the

external clock is not switching and in a low state (EXTCLK ≤

0.5 V), the input is disconnected from the output and draws less

than 0.3 A (typical) from the source.

The ADP2125 has an input voltage range of 2.1 V to 5.5 V,

allowing the use of single Li+/Li polymer cell, three-cell

alkaline, NiMH cell, and other standard power sources. The

ADP2125 is internally compensated to minimize external

components and can source up to 500 mA. Other key features

such as cycle-by-cycle peak current limit, soft start, undervoltage

lockout (UVLO), output-to-ground short-circuit protection, and

thermal shutdown provide protection for internal and external

circuit components.

TYPICAL APPLICATION CIRCUIT

B2 A1

VIN

GND FB

EXTCLK NC

NC = NO CONNECT

OFF ON

2.2µF

OUT

4.7µF

INPUT

VOLTAGE

2.1V TO 5.5V

1.5µH

ADP2125

OUTPUT

VOLTAGE

1.26V

08774-002

Figure 1.

Summary of content (16 pages)

PAGE 1
Low Profile, 500 mA, 6 MHz, Synchronous, Step-Down, DC-to-DC Converter ADP2125 FEATURES GENERAL DESCRIPTION 1.26 V fixed output voltage Clock signal enable 6 MHz (maximum) operating frequency 500 mA continuous output current Input voltage: 2.1 V to 5.5 V 0.
PAGE 2
ADP2125 TABLE OF CONTENTS Features .............................................................................................. 1 Overview ..................................................................................... 10 Applications....................................................................................... 1 External Clock (EXTCLK) Enable ........................................... 10 General Description .........................................................................
PAGE 3
ADP2125 SPECIFICATIONS VIN = 3.6 V, VOUT = 1.26 V, TA = 25°C for typical specifications, and TA = TJ = −40°C to +85°C for minimum and maximum specifications, unless otherwise noted. All specifications at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC) methods. Typical specifications are not guaranteed. Table 1.
PAGE 4
ADP2125 TIMING DIAGRAM VIN × 90% VIN t7 VIN × 10% t6 t3 VOUT VOUT(NOM) × 10% t2 t5 08774-003 EXTCLK t1 Figure 2. I/O Timing Diagram Rev.
PAGE 5
ADP2125 ABSOLUTE MAXIMUM RATINGS ambient temperature can exceed the maximum limit as long as the junction temperature is within specification limits. Table 2. Parameter VIN to GND EXTCLK to GND SW, NC to GND FB (VIN ≥ 3.6 V) to GND FB (VIN < 3.6 V) to GND Operating Ambient Temperature (TA) Operating Junction Temperature (TJ) at ILOAD = 500 mA Soldering Conditions 1 Rating −0.3 V to +6 V −0.3 V to +6 V −0.3 V to VIN −0.3 V to +3.6 V −0.
PAGE 6
ADP2125 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS BALL A1 INDICATOR 1 2 NC VIN A SW EXTCLK B FB GND TOP VIEW BALL SIDE DOWN BUMPS ON OPPOSITE SIDE (Not to Scale) 08774-005 C Figure 3. Pin Configuration Table 4. Pin Function Descriptions Pin No. A1 Mnemonic NC B1 C1 SW FB A2 B2 C2 VIN EXTCLK GND Description No Connection. Any voltage applied to this pin must be between GND and VIN. Voltages above VIN or below GND exceed the absolute maximum ratings and may cause damage to the part.
PAGE 7
ADP2125 TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.6 V, fEXTCLK = 10 MHz, VOUT = 1.26 V, L = 1.8 μH (700 mA, 0603 package, LQM18PN1R8NC0), CIN = 2.2 μF (6.3 V, 0402 package, X5R, GRM155R60J225ME15), COUT = 4.7 μF (4 V, 0402 package, X5R, GRM155R60G475ME47), and TA = 25°C, unless otherwise noted. 1.263 100 90 1.262 60 50 40 30 VIN = 2.1V VIN = 2.7V VIN = 3.6V VIN = 4.8V VIN = 5.5V 10 1 10 100 1000 LOAD CURRENT (mA) 1.259 VIN = 2.1V VIN = 2.7V VIN = 3.6V VIN = 4.8V VIN = 5.5V 1.257 1 10 1.
PAGE 8
ADP2125 350 TA = –40°C TA = +25°C TA = +85°C ISW = 500mA OUTPUT VOLTAGE (20mV/DIV) 1.26V OFFSET P-CHANNEL R DSON (mΩ) 300 1 250 200 LOAD CURRENT (200mA/DIV) 100 2.1 2.6 3.1 3.6 4.1 4.6 5.1 INPUT VOLTAGE (V) TIME (20µs/DIV) Figure 10. PMOS Drain-to-Source On Resistance 450 Figure 13. Load Transient Response, 250 mA to 420 mA, VIN = 2.1 V TA = –40°C TA = +25°C TA = +85°C ISW = 500mA 400 N-CHANNEL R DSON (mΩ) VIN = 2.1V VOUT = 1.
PAGE 9
ADP2125 VIN = 3.6V VOUT = 1.26V NO LOAD OUTPUT VOLTAGE (500mV/DIV) OUTPUT VOLTAGE (200mV/DIV) 1 1 INDUCTOR CURRENT (200mA/DIV) INDUCTOR CURRENT (1A/DIV) 2 2 TIME (20µs/DIV) TIME (200µs/DIV) Figure 16. Startup, No Load VIN = 3.6V VOUT = 1.26V RLOAD = 3.6Ω 08774-118 EXTCLK (5V/DIV) 08774-116 3 Figure 18. Output Short-Circuit Response VIN = 3.6V OUTPUT VOLTAGE (500mV/DIV) OUTPUT VOLTAGE (10mV/DIV) 1.
PAGE 10
ADP2125 THEORY OF OPERATION VIN 2.1V TO 5.5V CIN 2.2µF A2 VIN PVIN VOUT FB AVIN C1 PDRIVE R1 PWM COMP EAMP R2 AGND BG RAMP COMPENSATION 6MHz OSCILLATOR RDSCHG 110Ω FB B1 NDRIVE V(VIN) SW C2 PILIM PREF SOFT START SHORT-CIRCUIT PROTECTION VOUT DISCHARGE ZXCOMP LOGIC AND PWM CONTROL L 1.5µH VOUT 1.26V COUT 4.
PAGE 11
ADP2125 PROTECTION FEATURES Overcurrent Protection To ensure that excessively high currents do not damage the inductor, the ADP2125 incorporates cycle-by-cycle overcurrent protection. This function is accomplished by monitoring the instantaneous peak current on the power PMOS switch. If this current exceeds the PMOS switch current limit (1 A typical), then the PMOS is immediately turned off. This minimizes the potential for damage to power components during certain faults and transient events.
PAGE 12
ADP2125 APPLICATIONS INFORMATION It is important that the inductor be capable of handling the maximum peak inductor current, IPK, determined by the following equation: The ADP2125 is designed to be compatible with chip inductors and multilayer ceramic capacitors that are ideal for their small footprint and low height. The recommended components for this application may change as this technology advances. Table 5, Table 6, and Table 7 list compatible inductors and capacitors.
PAGE 13
ADP2125 OUTPUT CAPACITOR SELECTION The output capacitor selection affects both the output voltage ripple and the loop dynamics of the converter. For a given loop crossover frequency (the frequency at which the loop gain drops to 0 dB), the maximum voltage transient excursion (overshoot) is inversely proportional to the value of the output capacitor. When choosing output capacitors, it is also important to account for the loss of capacitance due to output voltage dc bias.
PAGE 14
ADP2125 PCB LAYOUT GUIDELINES To ensure package reliability, consider the following guidelines when designing the footprint for the ADP2125. The BUMPED_CHIP device footprint must ultimately be determined according to application and customer specific reliability requirements, PCB fabrication quality, and PCB assembly capabilities. • 08774-022 • Figure 22. ADP2125 Recommended Top Layer Layout • • • • 08774-023 • Figure 23.
PAGE 15
ADP2125 OUTLINE DIMENSIONS 0.405 0.390 0.375 0.940 0.900 0.860 SEATING PLANE 2 1 A BALL A1 IDENTIFIER 1.340 1.300 1.260 0.170 TYP 0.80 BSC B 0.40 BSC C 0.05 NOM COPLANARITY 0.40 BSC BOTTOM VIEW 0.115 TYP (BALL SIDE UP) 082409-A TOP VIEW (BALL SIDE DOWN) DIRECTION OF FEED 08774-008 Figure 24. 6-Ball Bumped Bare Die Sales [BUMPED_CHIP] (CD-6-2) Dimensions shown in millimeters Figure 25. Tape and Reel Orientation for ADP2125 ORDERING GUIDE Model 1 ADP2125BCDZ-1.26R7 ADP2125B-1.