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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
April 2005
FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Features
96% Efficiency, Synchronous Operation Adjustable Output Voltage Options from 0.8V to VIN 2.5V to 5.5V Input Voltage Range Up to 1A Output Current Fixed Frequency 1.3MHz PWM Operation High Efficiency Power Save Mode 100% Duty Cycle Low Dropout Operation Soft Start Output Over-Voltage Protection Dynamic Output Voltage Positioning 25A Quiescent Current Thermal Shutdown and Short Circuit Protection Pb-Free 3x3mm 6-Lead MLP Package
Description
Designed for use in battery-powered applications, the FAN2001/ FAN2002 is a high-efficiency, low-noise synchronous PWM current mode and Pulse Skip (Power Save) mode DC-DC converter. It can provide up to 1A of output current over a wide input range from 2.5V to 5.5V. The output voltage can be externally adjusted over a wide range of 0.8V to 5.5V by means of an external voltage divider. 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 over to current mode PWM control, operating at 1.3 MHz. A current mode control loop with fast transient response ensures excellent line and load regulation. To achieve high efficiency and ensure long battery life, the quiescent current is reduced to 25A in Power Save mode, and the supply current drops below 1A in shut-down mode. The FAN2001/FAN2002 is available in a 3x3mm 6-lead MLP package.
Applications
Pocket PCs, PDAs Cell Phones Battery-Powered Portable Devices Digital Cameras Hard Disk Drives Set-Top-Boxes Point-of-Load Power Notebook Computers
Communications Equipment
Typical Application
VIN CIN 10F EN
3
SW
1 2 6
3.3H NC FB R2 10K R1 5K
VOUT 1.2V (1A) COUT 2 x 10F
VOUT 1.2V (1A) 2 x 10F R2 10K R1 5K L1 3.3H
FB PGND SW
PGND
1 2 3
6
EN VIN PVIN 10F
P1 (AGND)
5 4
P1 (AGND)
5 4
FAN2001
FAN2002
Figure 1. Typical Application
FAN2001/FAN2002 Rev. 1.0.2
(c)2005 Fairchild Semiconductor Corporation
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Pin Assignment
Top View
VIN PGND EN
1
6
SW NC FB
FB PGND SW
1
6
EN VIN PVIN
P1
2 3
P1
2 3
(AGND)
5 4
(AGND)
5 4
FAN2001 3x3mm 6-Lead MLP
FAN2002
Figure 2. Pin Assignment
Pin Description
FAN2001 (3x3mm 6-Lead MLP)
Pin No.
P1 1 2 3 4 5 6
Pin Name
AGND VIN PGND EN FB NC SW Supply Voltage Input.
Pin Description
Analog Ground. P1 must be soldered to the PCB ground.
Power Ground. This pin is connected to the internal MOSFET switches. This pin must be externally connected to AGND. Enable Input. Logic high enables the chip and logic low disables the chip, reducing the supply current to less than 1A. Do not float this pin. Feedback Input. Adjustable voltage option, connect this pin to the resistor divider. No Connection Pin. Switching Node. This pin is connected to the internal MOSFET switches.
FAN2002 (3x3mm 6-Lead MLP)
Pin No.
P1 1 2 3 4 5 6
Pin Name
AGND FB PGND SW PVIN VIN EN
Pin Description
Analog Ground. P1 must be soldered to the PCB ground. Feedback Input. Adjustable voltage option, connect this pin to the resistor divider. Power Ground. This pin is connected to the internal MOSFET switches. This pin must be externally connected to AGND. Switching Node. This pin is connected to the internal MOSFET switches. Supply Voltage Input. This pin is connected to the internal MOSFET switches. Supply Voltage Input. Enable Input. Logic high enables the chip and logic low disables the chip, reducing the supply current to less than 1A. Do not float this pin.
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Absolute Maximum Ratings (Note1)
Parameter
VIN, PVIN Voltage On Any Other Pin Lead Soldering Temperature (10 seconds) Junction Temperature Storage Temperature Thermal Resistance-Junction to Tab (JC), 3x3mm 6-lead MLP (Note 2) Electrostatic Discharge Protection (ESD) Level (Note 3) HBM CDM 4 1 -65
Min
-0.3 -0.3
Max
7 VIN 260 150 150 8
Unit
V V C C C C/W kV
Recommended Operating Conditions
Parameter
Supply Voltage Range Output Voltage Range, Adjustable Version Output Current Inductor (Note 4) Input Capacitor (Note 4) Output Capacitor (Note 4) Operating Ambient Temperature Range Operating Junction Temperature Range -40 -40 3.3 10 2 x 10 +85 +125
Min
2.5 0.8
Typ
Max
5.5 VIN 1
Unit
V V A H F F C C
Notes: 1. Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and 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. Unless otherwise specified, all other voltages are referenced to AGND. 2. Junction to ambient thermal resistance, JA, is a strong function of PCB material, board thickness, thickness and number of copper planes, number of via used, diameter of via used, available copper surface, and attached heat sink characteristics. 3. Using Mil Std. 883E, method 3015.7(Human Body Model) and EIA/JESD22C101-A (Charge Device Model). 4. Refer to the applications section for further details.
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Electrical Characteristics
VIN = VOUT + 0.6V(min. 2.5V) to 5.5V, IOUT = 350mA, VOUT =1.2V, EN = VIN, TA = -40C to +85C, Unless otherwise noted. Typical values are at TA = 25C. Symbol
VIN IQ
Parameter
Input Voltage Quiescent Current
Conditions
0 mA IOUT 600 mA 0 mA IOUT 1000 mA IOUT = 0mA, Device is not switching IOUT = 0mA, Device is switching (Note 5) R2 =10K R2 =100K
Min.
2.5 2.7
Typ.
Max.
5.5 5.5
Units
V V
20 50 25 0.1 1.9 1.3 2.1 150
35
A A A A
V mV V
Shutdown Supply Current Undervoltage Threshold VENH VENL IEN RDS-ON
EN = GND
1 2.3
Lockout VIN Rising Hysteresis
Enable High Input Voltage Enable Low Input Voltage EN input bias current PMOS On Resistance NMOS On Resistance EN = VIN or GND VIN = VGS = 5.5V VIN = VGS = 2.5V VIN = VGS = 5.5V VIN = VGS = 2.5V 2.5V < VIN < 5.5V VDS = 5.5V VDS = 5.5V IOUT 10 mA 350 mA IOUT 1000 mA
0.4 0.01 250 300 200 250 1300 1000 1500 1300 0.1 0.1 0.16 0.15 0.8 -3 150 20 800 +3 0.1 350 400 300 350 2000 1500 1 1
V
A
m m mA KHz
ILIM Ilkg_(N) Ilkg_(P)
P-channel current limit Oscillator frequency N-channel leakage current P-channel leakage current Line regulation Load regulation
A A
%/V % V % C C S
Vref
Reference Voltage Output DC Voltage Accuracy 0 mA IOUT 1000 mA (Note 6) Rising Over-Temperature Protection PWM Mode Only 350 mA IOUT 1000 mA Temperature Hysteresis Start-Up Time IOUT = 1000 mA, COUT = 20 F
Notes: 5. Refer to the application section for further details. 6. For output voltages 1.2V a 40F output capacitor value is required to achieve a maximum output accuracy of 3% while operating in power save mode (PFM mode).
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Typical Performance Characteristics
TA = 25C, CIN = 10F, COUT = 20F, L = 3.3H, R2 = 10K, unless otherwise noted.
Efficiency vs. Load Current
100 95 90 100 95 90 85 80 75 70 65 60 55 50 45 40 35 0.1
Efficiency vs. Load Current
V OUT = 3.3V VIN = 3.9V R 2 = 100K
Efficiency (%)
85 80 75 70 65 60 1 10 100 1000
VIN = 5V VIN = 3.6V V OUT = 3V V OUT = 3.3V VIN = 3.6V VOUT = 1.2V
Efficiency (%)
VIN = 5.5V
1
10
100
1000
Load Current (mA)
Load Current (mA)
Efficiency vs. Load Current
100
V OUT = 1.2V
Output Voltage vs. Load Current
1.214 1.212 1.210 1.208 1.206 1.204 1.202 1.200 1.198 1.196 1.194 1.192
VIN = 5V
90
R 2 = 100K
70
V IN = 5.5V
60 50 40 30 0.1 1
V IN = 3. 6V
VIN = 2.5V
10
100
1000
Output Voltage (V)
80
Efficiency (%)
0
200
400
600
800
1000
Load Current (mA)
Load Current (mA)
Quiescent Current vs. Input Voltage
80 1400
Frequency vs. Temperature
Oscillator Frequency (kHz)
1380 1360 1340 1320 1300 1280 1260 1240 1220 1200 -40 -20 0 20
VIN = 2.5V V IN = 3.6V VIN = 5.5V
70
V OUT = 1. 2V
Quiescent Current (A)
60 50 40 30 20 10 0 2.5
R 2 = 100K R 2 = 10K
3.0
3.5
4.0
4.5
5.0
5.5
40
60
80
100
Input Voltage (V)
Temperature (C)
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Typical Performance Characteristics (Contd.)
TA = 25C, CIN = 10F, COUT = 20F, L = 3.3H, R2 = 10K, unless otherwise noted.
PWM Mode
SW Node Voltage (2V/div) Output SW Node Voltage Voltage (20mV/div) (2V/div)
Power Save Mode
Inductor Output Voltage Current (200mA/div) (5mV/div)
Time (1s/div)
Inductor Current (200mA/div)
Time (5s/div)
Inductor Load Current Output Current Step Voltage (50mV/div) (500mA/div)
100mA
600mA
Inductor Load Current Current Step (500mA/div)
Load Transient Response
Load Transient Response
600mA
VOUT = 1.2V
100mA
VOUT = 1.2V
Time (10s/div)
Output Voltage (50mV/div)
Time (10s/div)
Voltage at Enable Pin (5V/Div)
Inductor Output Current Voltage (200mA/div) (500mV/div)
Voltage at Inductor Output Enable Pin Current Voltage (5V/Div) (500mV/div) (500mA/div)
Start-Up Response
Start-Up Response
VOUT = 1.2V IOUT = 10mA
VOUT = 1.2V IOUT = 1000mA
Time (100s/div)
Time (200s/div)
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Block Diagram
EN VIN
DIGITAL SOFT START IS REF PFM COMP
UNDER-VOLTAGE LOCKOUT
IS
CURRENT SENSE
FB ERROR AMP COMP 0.8V MOSFET DRIVER
LOGIC CONTROL
SW
GND
IS
OVER VOLTAGE COMP
OSC SLOPE COMPENSATION
REF
FB
NEG. LIMIT COMP
NEG. LIMIT SENSE
GND
Figure 3. Block Diagram
Detailed Operation Description
The FAN2001/FAN2002 is a step-down converter operating in a current-mode PFM/PWM architecture with a typical switching frequency of 1.3MHz. 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 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 Pchannel switch turns off and the N-channel turns on as the peak inductor current is reached (typical 450mA). 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 turn on of the N-channel rectifier switch. The device stays in sleep mode until the output voltage falls below the low threshold. The FAN2001/FAN2002 enters the PWM mode as soon as the output voltage can no longer be regulated in PFM with constant peak current.
PWM Mode
In PWM mode, the device operates at a fixed frequency of 1.3MHz. 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 1500mA). 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.
PFM (Power Save) Mode
As the load current decreases and the inductor current reaches negative value, the converter enters pulse-frequency-modulation (PFM) mode. The transition point for the PFM mode is given by the equation: I OUT = V OUT 1 - ( V OUT V IN ) x -----------------------------------------2xLxf
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 Pchannel transistor: VOUT = VIN - ILOAD x (RdsON + RL), where RdsON = P-channel switch ON resistance ILOAD = Output current RL = Inductor DC resistance
The typical output current when the device enters PFM mode is 150mA for input voltage of 3.6V and output voltage of 1.2V. In
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
UVLO and Soft Start
The reference and the circuit remain reset until the VIN crosses its UVLO threshold. The FAN2001/FAN2002 has an internal soft-start circuit that limits the in-rush 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 (1500mA). Typical start-up time for a 20F output capacitor and a load current of 1000mA is 800s.
This is calculated as follows: 1 - ( V OUT V IN ) I L = V OUT x ---------------------------------------Lxf where: IL = Inductor Ripple Current f = Switching Frequency L = Inductor Value Some recommended inductors are suggested in the table below:
Short Circuit Protection
The switch peak current is limited cycle-by-cycle to a typical value of 1500mA. In the event of an output voltage short circuit, the device operates with a frequency of 400kHz and minimum duty cycle, therefore the average input current is typically 200mA.
Inductor Value
3.3H 3.3H
Vendor
Panasonic Murata
Part Number
ELL6PM3R3N LQS66C3R3M04
Table 1: Recommended Inductors Capacitors Selection
For best performances, a low ESR input capacitor is required. A ceramic capacitor of at least 10F, placed as close to the VIN and AGND pins of the device is recommended. The output capacitor determines the output ripple and the transient response.
Thermal Shutdown
When the die temperature exceeds 150C, a reset occurs and will remain in effect until the die cools to 130C, at that time the circuit will be allowed to restart.
Applications Information
Setting the Output Voltage
The internal reference is 0.8V (Typical). The output voltage is divided by a resistor divider, R1 and R2 to the FB pin. The output voltage is given by: R1 V OUT = V REF 1 + ------ R 2 Where R1 + R2 < 800K. According to this equation, and assuming desired output voltage of 1.5096V, and given R2 = 10K, the calculated value of R1 is 8.87K. If quiescent current is a key design parameter a higher value feedback resistor can be used (e.g. R2 = 100K) and a small bypass capacitor of 10pF is required in parallel with the upper resistor as shown in Figure 4.
SW
1 2 3 6
Capacitor Value
10F
Vendor
Taiyo Yuden
Part Number
JMK212BJ106MG JMK316BJ106KL
TDK
C2012X5ROJ106K C3216X5ROJ106M
Murata
GRM32ER61C106K
Table 2: Recommended Capacitors PCB Layout Recommendations
The recommended PCB layout is shown in Figures 5 and 6. The inherently high peak currents and switching frequency of power supplies require a careful PCB layout design.
VIN CIN 10F EN PGND
VOUT Cf 50K 1.2V (1A) COUT 2 x 10F R2 100K
3.3H NC FB R1
P1 (AGND)
5 4
Figure 4. Setting the Output Voltage Inductor Selection
The inductor parameters directly related to the device's performances are saturation current and dc resistance. The FAN2001/ FAN2002 operates with a typical inductor value of 3.3H. 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.
Figure 5. Recommended PCB Layout (FAN2001)
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Therefore, use wide traces for high current paths and place the input capacitor, the inductor, and the output capacitor as close as possible to the integrated circuit terminals. In order to minimize voltage stress to the device resulting from ever present switching spikes, use an input bypass capacitor with low ESR. Note that the peak amplitude of the switching spikes depends upon the load current; the higher the load current, the higher the switching spikes. The resistor divider that sets the output voltage should be routed away from the inductor to avoid RF coupling. The ground plane at the bottom side of the PCB acts as an electromagnetic shield to reduce EMI. For more board layout recommendations download the application note "PCB Grounding System and FAN2001/FAN2011 High Performance DC-DC Converters" (AN-42036).
Figure 6. Recommended PCB Layout (FAN2002)
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FAN2001/FAN2002 1A High-Efficiency Step-Down DC-DC Converter
Mechanical Dimensions
3x3mm 6-Lead MLP
Ordering Information
Product Number
FAN2001 FAN2002
Output Voltage
Adjustable Adjustable
Package Type
3x3mm 6-Lead MLP 3x3mm 6-Lead MLP
Order Code
FAN2001MPX FAN2002MPX
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FAN2001/FAN2002 1A 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 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 FAIRCHILD'S 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. I15
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