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FAN5307 High-Efficiency Step-Down DC-DC Converter
January 2006
FAN5307 High-Efficiency Step-Down DC-DC Converter
Features

General Description
The FAN5307, a high efficiency low noise synchronous PWM current mode and Pulse Skip (Power Save) mode DC-DC converter is designed for battery-powered applications. It provides up to 300mA of output current over a wide input range from 2.5V to 5.5V. The output voltage can be either internally fixed or externally adjustable over a wide range of 0.7V to 5.5V VIN by an external voltage divider. Custom output voltages are also available. Contact a Fairchild sales representative for customized output voltage options. At moderate and light loads pulse skipping modulation is used. Dynamic voltage positioning is applied, and the output voltage is shifted 0.8% above nominal value for increased headroom during load transients. At higher loads the system automatically switches to current mode PWM control, operating at 1 MHz. A current mode control loop with fast transient response ensures excellent line and load regulation. In Power Save mode, the quiescent current is reduced to 15A in order to achieve high efficiency and to ensure long battery life. In shut-down mode, the supply current drops below 1A. The device is available in 5-lead SOT-23 and 6-lead MLP 3x3mm packages.
95% Efficiency, Synchronous Operation Adjustable Output Voltage Option from 0.7V to VIN 2.5V to 5.5V Input Voltage Range Customized Fixed Output Voltage Options Up to 300mA Output Current Fixed Frequency 1MHz PWM Operation High Efficiency Power Save Mode 100% Duty Cycle Low Dropout Operation Soft Start Dynamic Output Voltage Positioning 15A Quiescent Current Excellent Load Transient Response 5-Lead SOT-23 Package 6-Lead MLP 3x3mm Package
Applications
Pocket PCs, PDAs Cell Phones Battery-Powered Portable Devices Digital Cameras Low Power DSP Supplies
Typical Application
EFFICIENCY vs. LOAD CURRENT VOUT = 1.8V 100 95 90 Efficiency [%] 85 80 75 70 65 0.01 0.1 1 10 100 1000
VIN=3.6V VIN=5.5V VIN=2.5V
Load Current [mA]
(c)2005 Fairchild Semiconductor Corporation
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Pin Assignment
Pin Description
5-Lead SOT-23 Pin No.
1 2 3 4 5
Pin Name
VIN GND EN FB LX
Pin Description
Supply voltage input. Ground. Enable Input. Logic high enables the chip and logic low disables the chip and reduces supply current to <1A. Do not float this pin. Feedback Input. In case of fixed voltage options, connect this pin directly to the output. For an adjustable voltage option, connect this pin to the resistor divider. Inductor pin. This pin is connected to the internal MOSFET switches.
6-Lead 3x3mm MLP Pin No.
1 2 3 4 5 6
Pin Name
EN GND VIN LX PGND FB
Pin Description
Enable Input. Logic high enables the chip and logic low disables the chip and reduces supply current to <1A. Do not float this pin. Reference ground. Supply voltage input. Inductor pin. This pin is connected to the internal MOSFET switches. Power ground. Internal N-channel MOSFET is connected to this pin. Feedback Input. In case of fixed voltage options, connect this pin directly to the output. For an adjustable voltage option, connect this pin to the resistor divider.
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Absolute Maximum Ratings
Parameter
VIN Voltage on any other pin Thermal Resistance (Note 1) Lead Soldering Temperature (10 seconds) Storage Temperature Electrostatic Discharge (ESD) Protection Level (Note 2) HBM CDM -65 4 1 Junction to case, SOT-23 Junction to tab, MLP 3x3
Min
-0.3 GND-0.3
Max
6.5 VIN + 0.3 130 8 260 150
Unit
V V C/W C C kV
Recommended Operating Conditions
Parameter
Supply Voltage Range Output Voltage Range, Adjustable Version Output Current Inductor (Note 3) Input Capacitor (Note 3) Output Capacitor (Note 3) Operating Ambient Temperature Range Operating Junction Temperature Range -40 -40 10 4.7 10 +85 +125
Min
2.5 0.7
Typ
Max
5.5 VIN 300
Unit
V V mA H F F C C
Notes: 1. Junction to ambient thermal resistance, JA, is a strong function of PCB material, board thickness, thickness and number of copper planes, number of vias used, diameter of via used, available copper surface, and attached heat sink characteristics. 2. Using Mil Std. 883E, method 3015.7(Human Body Model) and EIA/JESD22C101-A (Charge Device Model). 3. Refer to the applications section for further details.
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FAN5307 High-Efficiency Step-Down DC-DC Converter
General Electrical Characteristics
VIN = 2.5V to 5.5V, IOUT = 200mA, EN = VIN, CIN = 4.7F, COUT = 22F, LX = 10H, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = 25C.
Parameter
Quiescent Current Shutdown Supply Current Enable High Input Voltage Enable Low Input Voltage En Input Bias Current PMOS On Resistance NMOS On Resistance P-channel Current Limit N-channel Leakage Current P-channel Leakage Current Switching Frequency Line Regulation Load Regulation (6-Lead 3x3mm MLP) Load Regulation (5-Lead SOT-23) Output Voltage Accuracy (5-Lead SOT-23)
Conditions
Input Voltage IOUT = 0mA, Device is not switching EN = GND
Min.
2.5
Typ.
15 0.1
Max.
5.5 30 1 0.4
Units
V A A V V A m m mA A A kHz %/V % / mA % / mA
1.3 EN = VIN or GND VIN = VGS = 3.6V VIN = VGS = 2.5V VIN = VGS = 3.6V VIN = VGS = 2.5V 2.5V < VIN < 5.5V VDS = 5.5V VDS = 5.5V 800 VIN = 2.5 to 5.5V, IOUT = 10mA 100mA IOUT 300mA 100mA IOUT 300mA VIN = 2.5 to 4.5V, 0mA IOUT 300mA VIN = 2.5 to 5.5V, 0mA IOUT 300mA -4 -5 0.1 0.1 -4 400 0.01 530 670 430 530 520 0.1 0.1 1000 0.16 0.0014 0.0022 4 4 1 1 4 0.1 690 850 540 660 700 1 1 1200
% % A A %
Leakage Current into SW Pin Reverse Leakage Current into pin SW Output Voltage Accuracy (6-Lead 3x3mm MLP)
VIN > VOUT, 0V VSW VIN VIN = Open, EN = GND, VSW = 5.5V VIN = 2.5 to 5.5V, 0mA IOUT 300mA
Electrical Characteristics for Adjustable Version
VIN = 2.5V to 5.5V, IOUT = 200mA, EN = VIN, CIN = 4.7F, COUT = 22F, LX = 10H, TA = 25C.
Parameter
Feedback (FB) Voltage
Conditions
Min.
Typ.
0.5
Max.
Units
V
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Electrical Characteristics for Fixed VOUT = 1.8V Version
VIN = 2.5V to 5.5V, IOUT = 200mA, EN = VIN, CIN = 4.7F, COUT = 22F, LX = 10H, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = 25C.
Parameter
PFM to PWM Transition Voltage (Note 4) PFM to PWM Transition Voltage (Note 4) Output Voltage during Mode Transition (Note 5, 6) Over Voltage Clamp Threshold
Conditions
VIN = 3.7V, TA = 25C, 0.1mA IOUT 300mA VIN = 4.2V, TA = 25C, 0.1mA IOUT 300mA
Min.
Typ.
Max.
72 72
Units
mV mV V V
1.7 Incl. line, load, load transients, and temperature 1.878
1.93 1.93
Note: 4. Transition voltage is defined as the difference between the output voltage measured at 0.1mA (PFM mode) and 300mA (PWM mode), respectively. 5.
ILOAD (mA) 200
tr = 10S tf = 2S
2 0 0.01
ss
0.587 0.589
4.6
Time (mSec)
Load Transient Response Test Waveform
6. These limits also apply to any mode transition caused by any kind of load transition within specified output current range.
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Typical Performance Characteristics
(TA = 25C, CIN = COUT = 10F, L = 10H, VOUT = 1.8V, unless otherwise noted.)
LINE TRANSIENT RESPONSE START-UP
LOAD TRANSIENT RESPONSE
EFFICIENCY vs. LOAD CURRENT VOUT = 1.8V 100 No Load Quiescent Current [A] 95 90 Efficiency [%] 85 80 75 70 65 0.01 0.1 1 10 100 1000
VIN=3.6V VIN=5.5V VIN=2.5V
NO LOAD QUIESCENT CURRENT vs. INPUT VOLTAGE 26 24 22 20 18 16 14 2.5
TA=-40C TA=+25C TA=+85C
3.0
Load Current [mA]
3.5 4.0 4.5 Input Voltage [V]
5.0
5.5
FREQUENCY vs. TEMPERATURE 1060 1040 1020 Frequency [kHz] 1000 980 960 940 920 900 880 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 Temperature [C]
VIN=2.5V VIN=3.6V VIN=5.5V
POWER SAVE (PFM) MODE OPERATION
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Block Diagram
EN VIN
DIGITAL SOFT START IS
PFM COMPARATOR
UNDER VOLTAGE LOCKOUT
IS
CURRENT SENSE
REF
FB
ERROR AMPLIFIER COMPARATOR
LOGIC CONTROL
MOSFET DRIVER
LX
0.5V
GND IS
OVER VOLTAGE COMPARATOR
REF OSC SLOPE COMPENSATION
FB
NEG. LIMIT COMPARATOR
NEG. LIMIT SENSE
GND
Detailed Operation Description
The FAN5307 is a step-down converter operating in a current-mode PFM/PWM architecture with a typical switching frequency of 1MHz. At moderate to heavy loads, the converter operates in pulse-width-modulation (PWM) mode. At light loads the converter enters a power-save mode (PFM pulse skipping) to keep the efficiency high.
PFM (Power Save) Mode
As the load current decreases and the peak inductor current no longer reaches the typical threshold of 80mA, the converter enters pulse-frequency-modulation (PFM) mode. In PFM mode the device operates with a variable frequency and constant peak current thus reducing the quiescent current to minimum. Consequently, the high efficiency is maintained at light loads. As soon as the output voltage falls below a threshold, set at 0.8% above the nominal value, the P-channel transistor is turned on and the inductor current ramps up. The P-channel switch turns off and the N-channel turns on as the peak inductor current is reached (typical 140mA). The N-channel transistor is turned off before the inductor current becomes negative. At this time the P-channel is switched on again starting the next pulse. The converter continues these pulses until the high threshold (typical 1.6% above nominal value) is reached. A higher output voltage in PFM mode gives additional headroom for the voltage drop during a load transient from light to full load. The voltage overshoot during this load transient is also minimized due to active regulation during turning on the
PWM Mode
In PWM mode, the device operates at a fixed frequency of 1MHz. At the beginning of each clock cycle, the P-channel transistor is turned on. The inductor current ramps up and is monitored via an internal circuit. The P-channel switch is turned off when the sensed current causes the PWM comparator to trip when the output voltage is in regulation or when the inductor current reaches the current limit (set internally to typically 520mA). After a minimum dead time the N-channel transistor is turned on and the inductor current ramps down. As the clock cycle is completed, the N-channel switch is turned off and the next clock cycle starts.
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FAN5307 High-Efficiency Step-Down DC-DC Converter
N-channel rectifier switch. The device stays in sleep mode until the output voltage falls below the low threshold. The FAN5307 enters the PWM mode as soon as the output voltage can no longer be regulated in PFM with constant peak current.
Soft Start
The FAN5307 has an internal soft-start circuit that limits the inrush current during start-up. This prevents possible voltage drops of the input voltage and eliminates the output voltage overshoot. The soft-start is implemented as a digital circuit increasing the switch current in four steps to the P-channel current limit (520mA). Typical start-up time for a 10F output capacitor and a load current of 200mA is 500s.
100% Duty Cycle Operation
As the input voltage approaches the output voltage and the duty cycle exceeds the typical 95%, the converter turns the P-channel transistor continuously on. In this mode the output voltage is equal to the input voltage minus the voltage drop across the P-channel transistor: VOUT = VIN - ILOAD x (RdsON + RL), where RdsON = P-channel switch ON resistance ILOAD = Output current RL = Inductor DC resistance
Short-Circuit Protection
The switch peak current is limited cycle by cycle to a typical value of 520mA. In the event of a output voltage short circuit the device operates at minimum duty cycle, therefore the average input current is typically 100mA.
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Application Information
Adjustable Output Voltage Version
The output voltage for the adjustable version is set by the external resistor divider, as shown below:
Input Capacitor Selection
For best performances, a low ESR input capacitor is required. A ceramic capacitor of at least 4.7F, placed as close to the input pin of the device is recommended.
Output Capacitor Selection
The FAN5307's switching frequency of 1MHz allows the use of a low ESR ceramic capacitor with a value of 10F to 22F. This provides low output voltage ripple. In power save mode the output voltage ripple is independent of the output capacitor value and the ripple is determined by the internal comparator thresholds. The typical output voltage ripple at light load is 1% of the nominal output voltage. Capacitor Value
4.7F 10F TDK 22F Murata
100k
and is calculated as: R1 V OUT = 0.5V x 1 + -----R2 To reduce noise sensitivity, R1 + R2 should not exceed 1M.
Vendor
Taiyo Yuden
Part Number
JMK212BY475MG JMK212BJ106MG JMK316BJ106KL C12012X5ROJ106K C3216X5ROJ106M GRM32DR60J226K
Inductor Selection
The inductor parameters directly related to device performances are saturation current and dc resistance. The FAN5307 operates with a typical inductor value of 10H. The lower the dc resistance, the higher the efficiency. For saturation current, the inductor should be rated higher than the maximum load current plus half of the inductor ripple current that is calculated as follows: 1 - ( V OUT V IN ) I L = V OUT x ----------------------------------------Lxf where: f = Switching Frequency L = Inductor Value IL = Inductor Ripple Current Inductor Value
10H
Table 2: Recommended Capacitors PCB Layout Recommendations
The inherently high peak currents and switching fre-
quency of the power supplies require a careful PCB layout design. Therefore, use wide traces for the high current path and place the input capacitor, the inductor, and the output capacitor as close as possible to the integrated circuit terminals. For the adjustable version the resistor divider should be routed away from the inductor to avoid electromagnetic interference. The 6-lead MLP version of the FAN5307 separates the high current ground from the reference ground, therefore it is more tolerant to the PCB layout design and shows better performance.
Vendor
Sumida
Part Number
CDRH5D28-100 CDRH5D18-100 CDRH4D28-100
Performance
High Efficiency
Murata 6.8H 10H Sumida
LQH66SN100M01L CDRH3D16-6R8 CDRH4D18-100 CR32-100 CR43-100 Smallest Solution
Murata
LQH4C100K04
Table 1: Recommended Inductors
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Mechanical Dimensions
6-Lead 3x3mm MLP Package
2.45 0.15 C 3.0
2X
2.10 3.50
1.65 3.0 (0.70)
0.15
C
0.95 TYP
0.65 TYP
2X TOP VIEW
0.8 MAX 0.10 C (0.20) 0.08 C
RECOMMENDED LAND PATTERN
0.05 0.00
SEATING PLANE
SIDE VIEW
PIN #1 IDENT
2.25
1
0.45 0.20
3
1.65
0.2 MIN 0.95
6
1.90
4
0.30~0.45 0.10 0.05 CAB C
BOTTOM VIEW
NOTES:
A. CONFORMS TO JEDEC REGISTRATION MO-229, VARIATION WEEA, DATED 11/2001 B. DIMENSIONS ARE IN MILLIMETERS. C. DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Mechanical Dimensions
5-Lead SOT-23 Package
B e c E H e1 D A A1 L
Symbol A A1 B c D E e e1 H L
Inches Min .035 .000 .008 .003 .106 .059 Max .057 .006 .020 .010 .122 .071
Millimeters Min .90 .00 .20 .08 2.70 1.50 Max 1.45 .15 .50 .25 3.10 1.80
Notes
Notes: 1. Package outline exclusive of mold flash & metal burr. 2. Package outline exclusive of solder plating. 3. EIAJ Ref Number SC_74A
.037 BSC .075 BSC .087 .004 0 .126 .024 10
.95 BSC 1.90 BSC 2.20 .10 0 3.20 .60 10
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FAN5307 High-Efficiency Step-Down DC-DC Converter
Ordering Information
Product Number VOUT (V)
1.8 1.8 FAN5307 1.5 1.5 Adjustable Adjustable
Package Type
5-Lead SOT-23 Tape and Reel 6-Lead 3x3mm MLP Tape and Reel 5-Lead SOT-23 Tape and Reel 6-Lead 3x3mm MLP Tape and Reel 5-Lead SOT-23 Tape and Reel 6-Lead 3x3mm MLP Tape and Reel
Order Code
FAN5307S18X FAN5307MP18X FAN5307S15X FAN5307MP15X FAN5307SX FAN5307MPX
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FAN5307 High-Efficiency Step-Down DC-DC Converter
TRADEMARKS
The following are registered and unregistered trademarks Fairchild Semiconductor owns or is authorized to use and is not intended to be an exhaustive list of all such trademarks.
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DISCLAIMER
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SuperSOTTM-6 SuperSOTTM-8 SyncFETTM TinyLogic(R) TINYOPTOTM TruTranslationTM UHCTM UltraFET(R) UniFETTM VCXTM WireTM
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILDiS PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 2. A critical component is any component of a life 1. Life support devices or systems are devices or support device or system whose failure to perform can systems which, (a) are intended for surgical implant into be reasonably expected to cause the failure of the life the body, or (b) support or sustain life, or (c) whose support device or system, or to affect its safety or failure to perform when properly used in accordance with instructions for use provided in the labeling, can be effectiveness. reasonably expected to result in significant injury to the user. PRODUCT STATUS DEFINITIONS Definition of Terms Datasheet Identification Advance Information Product Status Formative or In Design Definition This datasheet contains the design specifications for product development. Specifications may change in any manner without notice. This datasheet contains preliminary data, and supplementary data will be published at a later date. Fairchild Semiconductor reserves the right to make changes at any time without notice in order to improve design. This datasheet contains final specifications. Fairchild Semiconductor reserves the right to make changes at any time without notice in order to improve design.
Preliminary
First Production
No Identification Needed
Full Production
Obsolete
Not In Production
This datasheet contains specifications on a product that has been discontinued by Fairchild semiconductor. The datasheet is printed for reference information only.
Rev. I17
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