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Ultralow Profile, 500 mA, 6 MHz, Synchronous, Step-Down, DC-to-DC Converters
ADP2126/ADP2127
FEATURES
1.20 V and 1.26 V fixed output voltage options Clock signal enable Logic signal enable also available on certain models 6 MHz operating frequency Spread spectrum frequency modulation to reduce EMI 500 mA continuous output current Input voltage: 2.1 V to 5.5 V 0.3 A (typical) shutdown supply current Pin-selectable power-saving mode 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 0.330 mm height (maximum), 6-ball BUMPED_CHIP (ADP2126) 0.200 mm height (maximum), 6-pad EWLP (ADP2127)
TYPICAL APPLICATION CIRCUITS
INPUT VOLTAGE 2.1V TO 5.5V CIN 2.2F
ADP2126
A2
L 1.0H
VIN
SW B1
OUTPUT VOLTAGE 1.20V OR 1.26V COUT 2.2F
C2
GND
FB C1 MODE
A1
EXTCLK
B2
PWM AUTO OFF ON OR OFF
09658-001
09658-002
ON
*
*LOGIC HIGH ENABLE IS ONLY AVAILABLE ON CERTAIN MODELS.
Figure 1. ADP2126 0.33 mm Maximum Height Solution
INPUT VOLTAGE 2.1V TO 5.5V CIN 2 x 1F
ADP2127
A2 VIN
L 0.56H
SW B1
OUTPUT VOLTAGE 1.20V OR 1.26V COUT 2 x 1F
C2 GND
FB C1 MODE
A1
APPLICATIONS
Mobile phones Digital still/video cameras Digital audio Portable equipment Camera modules Image stabilization systems
EXTCLK
B2
PWM AUTO OFF ON OR OFF ON *
*LOGIC HIGH ENABLE IS ONLY AVAILABLE ON CERTAIN MODELS.
Figure 2. ADP2127 0.22 mm Maximum Height Solution
GENERAL DESCRIPTION
The ADP2126/ADP2127 are high frequency, step-down, dc-todc converters optimized for portable applications in which board area and battery life are critical constraints. The fixed 6 MHz operating frequency enables the use of tiny ceramic inductors and capacitors and the regulators use spread spectrum frequency modulation to reduce EMI. Additionally, synchronous rectification improves efficiency and results in fewer external components. At high load currents, the ADP2126/ADP2127 use a voltage regulating pulse-width modulation (PWM) mode that maintains a constant frequency with excellent stability and transient response. Light load operation is determined by the state of the MODE pin. In forced PWM mode, the converter continues operating in PWM for light loads. Under light load conditions in auto mode, the ADP2126/ADP2127 automatically enter a power-saving mode, which uses pulse frequency modulation (PFM) to reduce the effective switching frequency, thus ensuring the longest battery life in portable applications.
Rev. A
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.
The ADP2126/ADP2127 are enabled by a 6 MHz to 27 MHz external clock signal applied to the EXTCLK pin. Certain models can also be enabled with a logic high signal. When the external clock is not switching and in a low logic state, the ADP2126/ADP2127 stop regulating and shut down to draw less than 0.3 A (typical) from the source. The ADP2126/ADP2127 have 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 ADP2126/ADP2127 are 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.
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ADP2126/ADP2127 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 Typical Application Circuits............................................................ 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Diagrams.......................................................................... 4 Absolute Maximum Ratings............................................................ 5 Thermal Considerations.............................................................. 5 Thermal Resistance ...................................................................... 5 ESD Caution.................................................................................. 5 Pin Configuration and Function Descriptions............................. 6 Typical Performance Characteristics ............................................. 7 Theory of Operation ...................................................................... 11 Overview...................................................................................... 11 External Clock (EXTCLK) Enable ........................................... 11 Spread Spectrum Oscillator ...................................................... 12 Mode Selection ........................................................................... 12 Internal Control Features .......................................................... 12 Protection Features .................................................................... 13 Timing Constraints .................................................................... 13 Applications Information .............................................................. 14 Inductor Selection ...................................................................... 14 Input Capacitor Selection.......................................................... 14 Output Capacitor Selection....................................................... 15 Thermal Considerations............................................................ 15 PCB Layout Guidelines.................................................................. 16 Outline Dimensions ....................................................................... 17 Ordering Guide .......................................................................... 18
REVISION HISTORY
5/11--Rev. 0 to Rev. A Changes to Figure 35...................................................................... 17 5/11--Revision 0: Initial Version
Rev. A | Page 2 of 20
ADP2126/ADP2127 SPECIFICATIONS
VIN = 3.6 V, TA = 25C for typical specifications, and TA = TJ = -40C to +85C for minimum and maximum specifications, unless otherwise noted. All specifications at temperature extremes are guaranteed via correlation using the standard statistical quality control (SQC) methods. Typical specifications are not guaranteed. Table 1.
Parameter SUPPLY Operating Input Voltage Range PWM Mode Quiescent Current Auto Mode Quiescent Current Shutdown Current 1 UNDERVOLTAGE LOCKOUT Rising VIN Threshold Falling VIN Threshold OUTPUT Continuous Output Current 2 PWM Mode Output Accuracy 3 PFM Mode Output Accuracy3, 4 FB Bias Current FB Pull-Down Resistance SWITCHING CHARACTERISTICS PMOS On Resistance NMOS On Resistance SW Leakage Current PMOS Switch Current Limit PFM Current Limit Oscillator Frequency SHORT-CIRCUIT PROTECTION Rising VOUT Threshold Falling VOUT Threshold EXTCLK INPUT High Threshold Voltage Low Threshold Voltage Leakage Current Duty Cycle Operating Range Frequency Operating Range MODE INPUT LOGIC High Threshold Voltage Low Threshold Voltage Leakage Current THERMAL SHUTDOWN 5 Thermal Shutdown Threshold Thermal Shutdown Hysteresis Symbol VIN No load, VMODE = VIN No load, VMODE = 0 V, VFB > VOUT, SW = open VEXTCLK = 0 V, open loop Test Conditions/Comments Min 2.1 12 300 0.3 1.9 1.8 Typ Max 5.5 500 1.5 2.1 Unit V mA A A V V mA V V A m m A mA mA MHz V V V V A % MHz V V A C C
1.5 ILOAD VOUT VIN = 2.1 V to 5.5 V VIN = 2.1 V to 5.5 V, no load VIN = 2.1 V to 5.5 V VFB = VOUT VEXTCLK = 0 V, IFB = 10 mA ISW = 500 mA ISW = 500 mA VSW = 0 V, VIN = 5.5 V Open loop VMODE = 0 V, VIN = 3.6 V fSW 500 VOUT - 2% VOUT - 3%
RDSCHG
4 110 180 250 770 170 4.8 1000 260 6 0.55 0.52
VOUT + 2% VOUT + 3% 9 180 340 10 1291 305 6.8 0.7
0.4 VEXTCLK(H) VEXTCLK(L) DEXTCLK fEXTCLK VMODE(H) VMODE(L) VIN = 2.1 V to 5.5 V VIN = 2.1 V to 5.5 V VEXTCLK = 0 V, VIN = VMODE = 5.5 V PWM mode only VIN = 2.1 V to 5.5 V VIN = 2. 1 V to 5.5 V VIN = 5.5 V, VEXTCLK = 2.1 V to 5.5 V 1.3
0.01 40 6 1.3 0.005 146 13
0.4 1 60 27
0.4 1
Rev. A | Page 3 of 20
ADP2126/ADP2127
Parameter TIMING VIN High to EXTCLK On2 EXTCLK On to VOUT Rising EXTCLK On to VOUT Rising VOUT Power-Up Time (Soft Start)2 EXTCLK Off to VOUT Falling EXTCLK Off to VOUT Falling VOUT Power-Down Time Minimum Shutdown Time2 Minimum Power-Off Time2
1 2 3
Symbol t1 t2 (CLOCK) t2 (LOGIC) t3 t5 (CLOCK) t5 (LOGIC) t6 t5 + t6 t7
Test Conditions/Comments See Figure 3 and Figure 4 VIN = 2.1 V to 5.5 V DEXTCLK = 40% to 60%, fEXTCLK = 6 MHz DEXTCLK = 40% to 60%, fEXTCLK = 27 MHz EXTCLK = logic high COUT = 2.2 F, RLOAD = 3.6 DEXTCLK = 40% to 60%, fEXTCLK = 6 MHz to 27 MHz EXTCLK = logic high, no load COUT = 2.2 F, RLOAD = 3.6 COUT = 2.2 F, no load COUT = 2.2 F, no load
Min 200 250 250 285
Typ
Max
Unit s s s s s s s s s s s
320 320 315 70 9 0 16 465
400 400 385 200 17
1400 500
The total shutdown current is the addition of VIN shutdown current and SW leakage. Guaranteed by design. Transients not included in voltage accuracy specifications. 4 The PFM output voltage will be higher than the PWM output voltage. See the Typical Performance Characteristics section. 5 Thermal shutdown protection is only active in PWM mode.
TIMING DIAGRAMS
VIN VIN x 90%
t7 t6
VOUT(NOM) x 10%
VIN x 10%
t3
VOUT
t2
EXTCLK
t5
09658-003
t1
Figure 3. Clock Enable I/O Timing Diagram
VIN
VIN x 90%
t7 t6
VOUT(NOM) x 10%
VIN x 10%
t3
VOUT
t2
EXTCLK
t5
09658-004
t1
Figure 4. Logic Enable I/O Timing Diagram (Logic High Enable Feature Only Available on Certain Models)
Rev. A | Page 4 of 20
ADP2126/ADP2127 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter VIN to GND EXTCLK to GND SW, MODE to GND FB 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 -40C to +85C1 -40C to +125C JEDEC J-STD-020
ambient temperature can exceed the maximum limit as long as the junction temperature is within specification limits. The operating junction temperature (TJ) of the device is dependent on the ambient temperature (TA), the power dissipation of the device (PD), and the junction-to-ambient thermal resistance of the package (JA). TJ is calculated using the following formula: TJ = TA + (PD x JA) (1) See the Applications Information section for further information on calculating the operating junction temperature for a specific application.
The maximum operating junction temperature (TJ (MAX)) supersedes the maximum operating ambient temperature (TA (MAX)). See the Thermal Considerations section for more information.
THERMAL RESISTANCE
JA of the package is based on modeling and calculation using a 4-layer board. JA is highly dependent on the application and board layout. In applications where high maximum power dissipation exists, attention to thermal board design is required. The value of JA may vary, depending on PCB material, layout, and environmental conditions. JA is specified for worst-case conditions, that is, a device soldered on a circuit board for surface-mount packages. JA is determined according to JEDEC Standard JESD51-9 on a 4-layer printed circuit board (PCB). Table 3. Thermal Resistance (4-Layer PCB)
Package Type 6-Ball Bumped Bare Die Sales 6-Pad Embedded Wafer Level Package JA 105 105 Unit C/W C/W
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. Absolute maximum ratings apply individually only, not in combination.
THERMAL CONSIDERATIONS
The maximum operating junction temperature (TJ (MAX)) supersedes the maximum operating ambient temperature (TA (MAX)) because the ADP2126/ADP2127 may be damaged when the junction temperature limits are exceeded. Monitoring ambient temperature does not guarantee that TJ is within the specified temperature limits. In applications with high power dissipation and poor PCB thermal resistance, the maximum ambient temperature may need to be derated. In applications with moderate power dissipation and good PCB thermal resistance, the maximum
ESD CAUTION
Rev. A | Page 5 of 20
ADP2126/ADP2127 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
BALL A1 INDICATOR 1 MODE A SW EXTCLK B FB C TOP VIEW BALL/PAD SIDE DOWN BUMPS/PADS ON OPPOSITE SIDE (Not to Scale) GND 2 VIN
Figure 5. Pin Configuration
Table 4. Pin Function Descriptions
Pin No. A1 Mnemonic MODE Description Mode Select. This pin toggles between auto mode (PFM and PWM switching) and PWM mode. Set MODE low to allow the part to operate in auto mode. Pull MODE high to force the part to operate in PWM mode. The voltage applied to MODE should never be higher than the voltage applied to VIN. Do not leave this pin floating. Power Supply Input. Switch Node. External Clock Enable Signal. The ADP2126/ADP2127 power up when a clock signal (6 MHz to 27 MHz) or a logic high signal (EXTCLK 1.3 V) is detected on this pin. (The logic high enable feature is only available on certain models.) Feedback Divider Input. Connect the output capacitor from FB to GND to set the output voltage ripple and to complete the control loop. Ground.
A2 B1 B2 C1 C2
VIN SW EXTCLK FB GND
Rev. A | Page 6 of 20
09658-005
ADP2126/ADP2127 TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6 V, fEXTCLK = 10 MHz, VOUT = 1.20 V, L = 1.0 H (CKP1608S1R0), CIN = 2.2 F (GRM153R60J225ME95), COUT = 2.2 F (GRM153R60G225M), and TA = 25C, unless otherwise noted.
90 AUTO MODE 80 70
OUTPUT VOLTAGE (V) EFFICIENCY (%)
1.205
60 50 40 PWM MODE 30 20 10 0 1 10 100 LOAD CURRENT (mA) VIN = 2.1V VIN = 2.5V VIN = 3.6V VIN = 4.2V VIN = 5.5V
09658-006
1.204
1.203 VIN = 2.1V VIN = 2.5V VIN = 3.6V VIN = 4.2V VIN = 5.5V 1 10 100 1000 LOAD CURRENT (mA)
09658-009
1.202
1000
Figure 6. Efficiency vs. Load Current
90
250
Figure 9. PWM Mode Output Voltage Accuracy
80
LOAD CURRENT (mA)
200 PWM OPERATION 150
EFFICIENCY (%)
70
60
100 PFM OPERATION 50
50
40
09658-007
2.6
3.1
3.6
4.1
4.6
5.1
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 7. Efficiency vs. Input Voltage
1.24
Figure 10. Auto Mode Switching Threshold vs. Input Voltage
60
1.23
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE RIPPLE (mV)
VIN = 2.1V VIN = 2.5V VIN = 3.6V VIN = 4.2V VIN = 5.5V
50
VIN = 2.1V VIN = 3.6V VIN = 5.5V
40
1.22
30
1.21
20
1.20
10
09658-008
1
10
100
1000
0
100
200
300
400
500
LOAD CURRENT (mA)
LOAD CURRENT (mA)
Figure 8. Auto Mode Output Voltage Accuracy
Figure 11. Output Voltage Ripple vs. Load Current
Rev. A | Page 7 of 20
09658-011
1.19
0
09658-010
30 2.1
ILOAD = 50mA, PWM MODE ILOAD = 100mA, PWM MODE ILOAD = 10mA, PFM MODE ILOAD = 50mA, PFM MODE ILOAD = 100mA, PFM MODE ILOAD = 250mA, PFM MODE
0 2.3
ADP2126/ADP2127
1.2 TA = -40C TA = +25C TA = +85C
450 ISW = 500mA 400
1.0
SHUTDOWN CURRENT (A)
TA = -40C TA = +25C TA = +105C
0.8
N-CHANNEL RDSON (m)
350
0.6
300
0.4
250
0.2
200
2.6
3.1
3.6
4.1
4.6
5.1
2.6
3.1
3.6
4.1
4.6
5.1
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 12. Shutdown Current vs. Input Voltage
500
PFM MODE QUIESCENT CURRENT (A)
Figure 15. NMOS Drain-to-Source On Resistance
400 ISW = 500mA
450
350
TA = -40C TA = +25C TA = +105C
400
P-CHANNEL RDSON (m)
300
350
250
300
200
250
2.6
3.1
3.6
4.1
4.6
5.1
2.6
3.1
3.6
4.1
4.6
5.1
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 13. PFM Mode Quiescent Current vs. Input Voltage
17
Figure 16. PMOS Drain-to-Source On Resistance
PWM MODE QUIESCENT CURRENT (mA)
OUTPUT VOLTAGE (200mV/DIV)
15
1
13
11
9
INDUCTOR CURRENT (1A/DIV)
7
2.6
3.1
3.6
4.1
4.6
5.1
INPUT VOLTAGE (V)
09658-014
5 2.1
TIME (200s/DIV)
Figure 14. PWM Mode Quiescent Current vs. Input Voltage
Figure 17. Output Short-Circuit Response
Rev. A | Page 8 of 20
09658-017
TA = -40C TA = +25C TA = +85C
4
09658-016
09658-013
200 2.1
TA = -40C TA = +25C TA = +85C
150
100 2.1
09658-015
09658-012
0 2.1
150 2.1
ADP2126/ADP2127
VIN = 2.1V OUTPUT VOLTAGE (50mV/DIV) 1.20V OFFSET
1
1
VIN = 2.1V
OUTPUT VOLTAGE (50mV/DIV) 1.20V OFFSET
LOAD CURRENT (200mA/DIV)
LOAD CURRENT (100mA/DIV)
4
09658-018 09658-021 09658-023 09658-022
4
TIME (40s/DIV)
TIME (20s/DIV)
Figure 18. Load Transient Response, 0 mA to 150 mA, VIN = 2.1 V
Figure 21. Load Transient Response, 250 mA to 420 mA, VIN = 2.1 V
VIN = 3.6V OUTPUT VOLTAGE (50mV/DIV) 1.20V OFFSET
1 1
VIN = 3.6V
OUTPUT VOLTAGE (50mV/DIV) 1.20V OFFSET
LOAD CURRENT (200mA/DIV)
LOAD CURRENT (100mA/DIV)
4
09658-019
4
TIME (40s/DIV)
TIME (20s/DIV)
Figure 19. Load Transient Response, 0 mA to 150 mA, VIN = 3.6 V
Figure 22. Load Transient Response, 250 mA to 420 mA, VIN = 3.6 V
VIN = 5.5V OUTPUT VOLTAGE (50mV/DIV) 1.20V OFFSET
1 1
VIN = 5.5V
OUTPUT VOLTAGE (50mV/DIV) 1.20V OFFSET
LOAD CURRENT (200mA/DIV)
LOAD CURRENT (100mA/DIV)
4
09658-020
4
TIME (40s/DIV)
TIME (20s/DIV)
Figure 20. Load Transient Response, 0 mA to150 mA, VIN = 5.5 V
Figure 23. Load Transient Response, 250 mA to 420 mA, VIN = 5.5 V
Rev. A | Page 9 of 20
ADP2126/ADP2127
NO LOAD OUTPUT VOLTAGE (500mV/DIV)
ILOAD = 100mA OUTPUT VOLTAGE (20mV/DIV) 1.20V OFFSET
1 1
INDUCTOR CURRENT (200mA/DIV)
INDUCTOR CURRENT (200mA/DIV)
4 4
EXTCLK PIN VOLTAGE (5V/DIV)
2
09658-024
SW PIN VOLTAGE (5V/DIV)
2
09658-027 09658-028
TIME (100s/DIV)
TIME (400ns/DIV)
Figure 24. Startup, No Load
Figure 27. Typical PFM Mode Operation, ILOAD = 100 mA
RLOAD = 3.6 OUTPUT VOLTAGE (500mV/DIV)
1
ILOAD = 150mA OUTPUT VOLTAGE (10mV/DIV) 1.20V OFFSET
1
INDUCTOR CURRENT (200mA/DIV)
4 4
INDUCTOR CURRENT (200mA/DIV) EXTCLK PIN VOLTAGE (5V/DIV)
SW PIN VOLTAGE (5V/DIV)
4
09658-025
2
TIME (100s/DIV)
TIME (100ns/DIV)
Figure 25. Startup, RLOAD = 3.6
Figure 28. Typical PWM Mode Operation, ILOAD = 150 mA
5.50
5.45
FREQUENCY (MHz)
5.40
5.35
5.30
5.25
09658-026
-2.0
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
2.0
TIME (ns)
Figure 26. Spread Spectrum Switching Frequency
Rev. A | Page 10 of 20
ADP2126/ADP2127 THEORY OF OPERATION
VIN 2.1V TO 5.5V CIN VIN
A2
VOUT
FB
C1
ADP2126/ADP2127
R1 R2 AGND BG COMPENSATION
RAMP V(VIN)
PVIN AVIN PDRIVE PWM COMP
EAMP
SHOOTTHROUGH CONTROL
NDRIVE PGND PILIM PREF AGND
B1
SW
L
VOUT 1.20V OR 1.26V COUT
C2
GND
AGND 6MHz OSCILLATOR
THERMAL SHUTDOWN SOFT START SHORT-CIRCUIT PROTECTION
FB RDSCHG 110 VOUT DISCHARGE AGND BG BANDGAP
FB
ZXCOMP LOGIC AND PFM/PWM CONTROL
NREF
CLK DETECT
THRESHOLD DETECT*
B2
THRESHOLD DETECT
A1
EXTCLK
MODE
PWM OFF ON OR OFF *THE LOGIC HIGH ENABLE FEATURE IS ONLY AVAILABLE ON CERTAIN MODELS.
09658-029
AUTO ON *
Figure 29. Internal Block Diagram
OVERVIEW
The ADP2126/ADP2127 are high efficiency, synchronous, stepdown, dc-to-dc regulators that operate from a 2.1 V to 5.5 V input voltage. They provide up to 500 mA of continuous output current at a fixed output voltage. The 6 MHz operating frequency enables the use of tiny external components. External control for mode selection provides a power-saving option. The internal control schemes of the ADP2126/ADP2127 give excellent stability and transient response. Other internal features, such as cycle-by-cycle peak current limit, soft start, undervoltage lockout, output-to-ground short-circuit protection, and thermal shutdown provide protection for internal circuit components.
EXTERNAL CLOCK (EXTCLK) ENABLE
The ADP2126/ADP2127 are enabled by a 6 MHz to 27 MHz external clock signal applied to the EXTCLK pin. Certain models can also be enabled with a logic high signal (see Figure 3, Figure 4, and Figure 29). When the ADP2126/ ADP2127 are enabled, the converter is able to power up, and the output voltage rises to its nominal value. When the external clock is not switching and in a low logic state, the ADP2126/ADP2127 stop regulating and shut down to draw less than 0.3 A (typical) from the source.
Rev. A | Page 11 of 20
ADP2126/ADP2127
SPREAD SPECTRUM OSCILLATOR
The ADP2126/ADP2127 incorporate spread spectrum functionality to modulate electromagnetic interference (EMI) for EMI sensitive applications. A typical switching converter with a regulated switching frequency has a narrow frequency spectrum centered at the target switching frequency. This results in a high spectral density around the target frequency with peak emission levels that can exceed the regulatory levels for EMI in many portable, cellular, and wireless applications. To maintain acceptable levels of EMI, the ADP2126/ADP2127 employs spread spectrum via a controlled variance of the switching frequency over a wider band of frequencies. Figure 26 shows the variance of the frequency over time. This distribution of the frequency content spreads the spectral density over a wider bandwidth, resulting in lower peak emission levels. When the upper level is reached, the output stage and most control circuitry turn off to reduce the quiescent current. During this stage, the output capacitor supplies the current to the load. As the output capacitor discharges and the output voltage reaches the lower PFM comparator threshold, switching resumes and the process repeats.
Mode Transition
When the MODE pin is low, the converter switches between PFM and PWM modes automatically to maintain optimal transient response and efficiency. The mode transition point depends on the input voltage. Hysteresis exists in the transition point to prevent instability and decreased efficiencies that could result if the converter were able to oscillate between PFM and PWM for a fixed input voltage and load current. See Figure 10 for the typical PFM and PWM mode boundaries of the ADP2126/ADP2127. A switch from PFM to PWM occurs when the output voltage dips below the nominal value of the output voltage option. Switching to PWM allows the converter to maintain efficiency and supply a larger current to the load. The output voltage in PFM mode is slightly higher to keep the ADP2126/ADP2127 from oscillating between modes, ensuring stable operation. The switch from PWM to PFM occurs when the output current is below the PFM threshold for multiple consecutive switching cycles. Switching to PFM allows the converter to save power by supplying the lighter load current with fewer switching cycles.
MODE SELECTION
The ADP2126/ADP2127 have two modes of operation (PWM mode and auto mode), determined by the state of the MODE pin. Pull the MODE pin high to force the converter to operate in PWM mode, regardless of the output current. Otherwise, set MODE low to put the converter into auto mode and allow the converter to automatically transition from PWM mode to the power-saving PFM mode at light load currents. Do not leave this pin floating.
Pulse-Width Modulation (PWM) Mode
The PWM mode forces the part to maintain a fixed frequency of 6 MHz (maximum) under all load conditions. The ADP2126/ ADP2127 use a proprietary, hybrid voltage-mode control scheme to control the duty cycle under all load current and line voltage variations. This control scheme provides excellent stability, transient response, and output regulation. PWM mode results in lower efficiencies at light load currents.
INTERNAL CONTROL FEATURES
Synchronous Rectification
In addition to the P-channel MOSFET switch, the ADP2126/ ADP2127 include an N-channel MOSFET switch to build the synchronous rectifier. The synchronous rectifier improves efficiency, especially for small load currents, and reduces cost and board space by eliminating the need for an external rectifier.
Auto Mode (PFM and PWM Switching)
Auto mode is a power-saving feature that enables the converter to switch between PWM and PFM in response to the output load. Auto mode is enabled when the MODE pin is pulled low. In auto mode, the ADP2126/ADP2127 operate in PFM mode for light load currents and switch to PWM mode for medium and heavy load currents.
Soft Start
To prevent excessive input inrush current at startup, the ADP2126/ ADP2127 operate with an internal soft start. When EXTCLK begins to oscillate, or when the part recovers from a fault (UVLO, TSD, or SCP), a soft start timer begins. During this time, the peak current limit is gradually increased to its maximum. The output voltage increases in stages to ensure that the converter is able to start up effectively and in proper sequence. After the soft start period expires, the peak PMOS switch current limit remains at 1 A (typical), and the part begins normal operation.
35BPulse Frequency Modulation (PFM) Mode
When the converter is operating under light load conditions, the effective switching frequency and supply current are decreased and varied using PFM to regulate the output voltage. This results in improved efficiencies and lower quiescent currents. In PFM mode, the converter only switches when necessary to keep the output voltage within the PFM limits set by an internal comparator. Switching stops when the upper limit is reached and resumes when the lower limit is reached.
Rev. A | Page 12 of 20
ADP2126/ADP2127
PROTECTION FEATURES
Overcurrent Protection
To ensure that excessively high currents do not damage the MOSFET switches, the ADP2126/ADP2127 incorporate cycle-bycycle 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.
Undervoltage Lockout (UVLO)
If the input voltage is below the UVLO threshold, the ADP2126/ ADP2127 automatically turn off the power switches and place the parts in a low power consumption mode. This prevents potentially erratic operation at low input voltages. The UVLO levels have approximately 100 mV of hysteresis to ensure glitch-free startup.
TIMING CONSTRAINTS
Shutdown Time
When the ADP2126/ADP2127 enter shutdown mode after the EXTCLK signal is removed, the ADP2126/ADP2127 must remain in shutdown mode for a minimum of 1400 s, if no load is applied, before the EXTCLK signal can be reapplied. This allows all internal nodes to discharge to an off state.
Output Short-Circuit Protection (SCP)
If the output voltage is shorted to GND, a standard dc-to-dc controller delivers maximum power into that short. This may result in a potentially catastrophic failure. To prevent this, the ADP2126/ADP2127 sense when the output voltage is below the SCP threshold (typically 0.52 V). At this point, the controller turns off for approximately 450 s and then automatically initiates a soft start sequence. This cycle repeats until the short is removed or the part is disabled. Figure 17 shows the operating behavior of the ADP2126/ADP2127 during a short-circuit fault. The SCP dramatically reduces the power delivered into the short circuit, yet still allows the converter to recover when the fault is removed.
Power-Off Time
When VIN drops, thereby triggering UVLO, the ADP2126/ ADP2127 have a minimum power-off time (t7) of 500 s that must elapse before VIN can be reapplied. This allows all internal nodes to discharge enough power so that all internal devices are in an off state.
09658-030
t7
VIN x 10%
Thermal Shutdown (TSD) Protection
The ADP2126/ADP2127 also include TSD protection when the part is in PWM mode only. If the die temperature exceeds 146C (typical), the TSD protection activates and turns off both MOSFET power devices. They remain off until the die temperature falls to 133C (typical), at which point the regulator restarts.
Figure 30. Power-Off Time
Rev. A | Page 13 of 20
ADP2126/ADP2127 APPLICATIONS INFORMATION
The low-profile ADP2126/ADP2127 are compatible with chip inductors and multilayer ceramic capacitors that are ideal for use in portable applications due to their small footprint and low height. The recommended components for low-profile applications may change as this technology advances. Table 5 and Table 6 list compatible inductors and capacitors. This section describes the selection of external components. The component value ranges are limited to optimize efficiency and transient performance while maintaining stability over the full operating range. It is important that the minimum dc current rating of the inductor be greater than the peak inductor current (IPK) in the application. IPK is calculated from
IPK = ILOAD(MAX) + IL/2
(3)
The dc current rating of the inductor should be greater than the calculated IPK to prevent core saturation.
INPUT CAPACITOR SELECTION
The input capacitor must be rated to support the maximum input operating voltage. Higher value input capacitors reduce the input voltage ripple caused by the switch currents on the VIN pin. Maximum rms input current for the application is calculated using
I RMS _ MAX (CIN ) = I LOAD ( MAX ) x VOUT x (V IN - VOUT ) V IN
INDUCTOR SELECTION
The high switching frequency of the ADP2126/ADP2127 allows for minimal output voltage ripple, even with small inductors. Inductor sizing is a trade-off between efficiency and transient response. A small value inductor leads to a larger inductor current ripple, which provides excellent transient response but degrades efficiency. A small footprint and low height chip inductor can be used for an overall smaller solution size but has a higher dc resistance (DCR) value and lower current rating that can degrade performance. Shielded ferrite core inductors are advantageous for their low core losses and low electromagnetic interference (EMI). For optimal performance and stability, use inductor values between 1.5 H and 0.5 H. Recommended inductors are shown in Table 5. The inductor peak-to-peak current ripple, IL, is calculated from
(4)
Place the input capacitor as close as possible to the VIN pin to minimize supply noise. In principle, different types of capacitors can be considered, but for battery-powered applications, the best choice is the multilayer ceramic capacitor, due to its small size, low equivalent series resistance (ESR), and low equivalent series inductance (ESL). It is recommended that the VIN pin be bypassed with at least a 2.2 F input capacitor. For a 0.22 mm height solution using the ADP2127, at least 2 x 1.0 F capacitors will be necessary on the input. The input capacitor can be increased without any limit for better input voltage filtering. X5R or X7R dielectrics with a voltage rating of 6.3 V or higher are recommended.
I L =
VOUT x (V IN - VOUT ) V IN x L x f SW
(2)
where: fSW is the switching frequency. L is the inductor value. Table 5. Inductor Selection
Manufacturer Murata Taiyo Yuden Series LQM18PN1R0-A52 CKP1608S1R5M Inductance (H) 1.0 1.5 DCR (m) (typ) 520 420 Current Rating (mA) 500 500 Size (L x W x H) (mm) 1.6 x 0.8 x 0.33 1.6 x 0.8 x 0.33 Package 0603 0603
Table 6. Input/Output Capacitor Selection
Manufacturer Murata Taiyo Yuden Part Number GRM153R60J225ME95 GRM153R60G225M JMK105BJ225MP AMK105BJ225MP AMK105BJ105MC ADC105BJ105ME Capacitance (F) 2.2 2.2 2.2 2.2 1.0 1.0 Voltage Rating (V) 6.3 4 6.3 4 4 4 Temperature Coefficient X5R X5R X5R X5R X5R X5R Size (L x W x H) (mm) 1.0 x 0.5 x 0.33 1.0 x 0.5 x 0.33 1.0 x 0.5 x 0.33 1.0 x 0.5 x 0.33 1.0 x 0.5 x 0.22 1.0 x 0.5 x 0.20 Package 0402 0402 0402 0402 0402 0402
Rev. A | Page 14 of 20
ADP2126/ADP2127
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 important to account for the loss of capacitance due to output voltage dc bias. This may result in using a capacitor with a higher rated voltage to achieve the desired capacitance value. Additionally, if ceramic output capacitors are used, the capacitor's rms ripple current rating should always meet or exceed the application requirements. The rms ripple current is calculated from
The power dissipation (PD) of the ADP2126/ADP2127 is only a portion of the power loss of the overall application. For a given application with known operating conditions, the application power loss is calculated by combining the following equations for power loss (PLOSS) and efficiency (): PLOSS = PIN - POUT (8) (9)
POUT PIN
=
x 100
The resulting equation uses the output power and the efficiency to determine the PLOSS.
100 PLOSS = POUT - 1 (10)
I RMS (COUT ) =
1 23
x
VOUT x V IN ( MAX ) - VOUT L x f SW x V IN ( MAX )
(
)
(5)
At nominal load currents, the converter operates in forced PWM mode, and the overall output voltage ripple is the sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging the output capacitor. VOUT = IL x (ESR + 1/(8 x COUT x fSW)) The largest voltage ripple occurs at the highest input voltage. The ADP2126/ADP2127 are designed to operate with one small 2.2 F capacitor. For a 0.22 mm height solution using the ADP2127, at least 2 x 1.0 F capacitors will be necessary on the output. X5R or X7R dielectrics that have low ESR, low ESL, and a voltage rating of 4 V or higher are recommended. These low ESR components help the ADP2126/ADP2127 meet tight output voltage ripple specifications. (6)
The power loss calculated using this approach is the combined loss of the ADP2126/ADP2127 device (PD), the inductor (PL), input capacitor (PCIN), and the output capacitor (PCOUT), as shown in the following equation: PLOSS = PD + PL + PCIN + PCOUT (11) The power loss for the inductor, input capacitor, and output capacitor is calculated using PL = IRMS2 x DCR
I PCIN = RMS x ESR CIN 2 PCOUT = (IOUT)2 x ESRCOUT
2
(12)
(13) (14)
If multilayer chip capacitors with low ESR are used, the power loss in the input and output capacitors is negligible and PD + PL >> PCIN + PCOUT PLOSS PD + PL (15) (16)
THERMAL CONSIDERATIONS
The operating junction temperature (TJ) of the device is dependent on the ambient operating temperature (TA) of the application, the power dissipation of the ADP2126/ADP2127 (PD), and the junction-to-ambient thermal resistance of the package (JA). The operating junction temperature (TJ) is calculated from TJ = TA + (PD x JA) where JA is 105C/W, as provided in Table 3. The ADP2126/ADP2127 may be damaged when the operating junction temperature limits are exceeded. Monitoring ambient temperature does not guarantee that the junction temperature (TJ) is within the specified temperature limits.
*
The final equation for calculating PD can be used in Equation 7 to ensure that the operating junction temperature is not exceeded. 100 PD PLOSS - PL POUT - 1 - PL (17)
(7)
*
In applications with high PD and poor PCB thermal resistance, the maximum ambient temperature may need to be derated. In applications with moderate PD and good PCB thermal resistance, the maximum ambient temperature can exceed the maximum limit as long as the junction temperature is within specification limits.
Rev. A | Page 15 of 20
ADP2126/ADP2127 PCB LAYOUT GUIDELINES
To ensure package reliability, consider the following guidelines when designing the footprint for the ADP2126/ADP2127. The BUMPED_CHIP device footprint must ultimately be determined according to application and customer specific reliability requirements, PCB fabrication quality, and PCB assembly capabilities. * The Cu pad on the PCB for each solder bump should be 80% to 100% of the width of the solder bump. A smaller pad opening favors solder joint reliability (SJR) performance, whereas a larger pad opening favors drop test performance. The maximum pad size, including tolerance, should not exceed 180 m. Electroplated nickel, immersion gold (ENIG) and organic solderability preservative (OSP) were used for internal reliability testing and are recommended. Nonsolder mask defined (NSMD) Cu pads are recommended for the BUMPED_CHIP package. The solder mask opening should be approximately 100 m larger than the pad opening. The trace width should be less than two-thirds the size of the pad opening. The routing of traces from the Cu pads should be symmetrical in X and Y directions. Symmetrical routing of the traces prevents part rotation due to uneven solder wetting/surface tension forces. Stencil design is important for proper transfer of paste onto the Cu pads. Area ratio (AR), the relationship between the surface area of the stencil aperture and the inside surface area of the aperture walls, is critically important. Stencil thickness has the greatest impact on this ratio. AR values from 0.66 to 0.8 provide the best paste transfer efficiency and repeatability. The AR is calculated from Ap AR = Aw where: Ap is the area of the aperture opening. Aw is the wall area.
*
09658-031
* * * *
Figure 31. ADP2126/ADP2127 Recommended Top Layer Layout
*
Figure 32. ADP2126/ADP2127 Recommended Bottom Layer Layout
For high efficiency, good regulation, and stability, a well-designed and manufactured PCB is required. Use the following guidelines when designing PCBs: * * * Keep the low ESR input capacitor, CIN, close to VIN and GND. Keep high current traces as short and as wide as possible. Avoid routing high impedance traces near any node connected to SW or near the inductor to prevent radiated noise injection. Keep the low ESR output capacitor, COUT, close to the FB and GND pins of the ADP2126/ADP2127. Long trace lengths from the part to the output capacitor add series inductance that may cause instability or increased ripple.
*
Rev. A | Page 16 of 20
09658-032
ADP2126/ADP2127 OUTLINE DIMENSIONS
0.940 0.900 0.860
2 1 A
BALL A1 IDENTIFIER
1.340 1.300 1.260
0.80 REF
B
0.40 REF
C
TOP VIEW
(BALL SIDE DOWN)
0.40 REF BOTTOM VIEW 0.225 TYP COPLANARITY 0.05 NOM
(BALL SIDE UP)
0.330 0.315 0.300
END VIEW
0.190 0.170 0.150
0.09 TYP
Figure 33. 6-Ball Bumped Bare Die Sales [BUMPED_CHIP] (CD-6-4) Dimensions shown in millimeters
0.200 0.175 0.150
0.940 0.900 0.860
SEATING PLANE
BARE Cu FIDUCIAL 0.15 DIA.
BOTTOM VIEW
(PAD SIDE UP)
2
1
A
1.340 1.300 1.260
0.80 REF
B
0.40 PAD PITCH
TOP VIEW
(PAD SIDE DOWN)
C
DETAIL A
0.17 DIA. 0.40 REF
0.13 DIA.
DETAIL A
ROTATED 90 CCW
Figure 34. 6-Pad Embedded Wafer Level Package [EWLP] (CN-6-1) Dimensions shown in millimeters
THE ADP2126 HAS AN A1 BALL IDENTIFIER THAT IS VISIBLE ON THE TOP OF THE PART. THE ADP2127 HAS NO VISIBLE MARKING ON THE TOP, BUT THE A1 PIN LOCATION IS THE SAME.
12 A B C DIRECTION OF FEED
09658-035
Figure 35. Tape and Reel Orientation for ADP2126/ADP2127
Rev. A | Page 17 of 20
04-25-2011-A
0.008 MIN
05-10-2010-A
SEATING PLANE
ADP2126/ADP2127
ORDERING GUIDE
Model 1 ADP2126ACDZ-1.20R7 ADP2127ACNZ1.260R7 ADP2126-1.2-EVALZ ADP2127-1.26-EVALZ
1 2
Output Voltage 1.20 V 1.26 V 1.20 V 1.26 V
EXTCLK Enable Type Clock and logic Clock only Clock and logic Clock only
Temperature Range -40C to +85C -40C to +85C
Package Description 6-Ball Bumped Bare Die Sales [BUMPED_CHIP] 6-Pad Embedded Wafer Level [EWLP] Evaluation Board for ADP2126 Evaluation Board for ADP2127
Package Option 2 CD-6-4 CN-6-1
Branding 3 LHY
Z = RoHS Compliant Part. These package options are halide free. 3 The ADP2127 does not have a Pin 1 indicator or a branding code. The bare Cu fiducial on the pad side can be used for device orientation.
Rev. A | Page 18 of 20
ADP2126/ADP2127 NOTES
Rev. A | Page 19 of 20
ADP2126/ADP2127 NOTES
(c)2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09658-0-5/11(A)
Rev. A | Page 20 of 20

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