View SP6669_4554654.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

SP6669
1.5MHZ, 600mA SYNCHRONOUS STEP DOWN CONVERTER
FEATURES Up to 600mA Output Current
Up to 95% Efficiency 1.5MHz Constant Frequency Operation Low Dropout Operation Mode: 100% Duty Cycle
Output Voltages as low as 0.6V No Schottky Diode Required 200A Quiescent Current (no load) Excellent Line and Load Transient Response Over-Temperature Protection 2.5V to 5.5V Input Voltage Range Lead Free SOT23-5 Package APPLICATIONS Cellular Phones Wireless Networking Digital Cameras Portable Media Players Bluetooth Devices Portable Instruments DESCRIPTION
The SP6669 is a 600mA synchronous buck converter using a constant frequency current mode architecture with pulse width modulation (PWM) for low output voltage ripple and fixed frequency noise, a pulse skip mode (PSM) for light load efficiency and a LDO mode for 100% duty cycle. With a 2.5V to 5.5V input voltage range and a 1.5MHz switching frequency, the SP6669 allows the use of small surface mount inductors and capacitors ideal for battery powered portable applications. The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.6V feedback reference voltage. The SP6669 is available in an adjustable output voltage version, using an external resistor divider circuit, as well as fixed output voltage versions of 1.2V, 1.5V and 1.8V. The SP6669 is available in a 5 pin SOT-23 package.
TYPICAL APPLICATION CIRCUIT
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 1/10
BLOCK DIAGRAM
Fig.1: SP6669 Block Diagram
PIN DESCRIPTION
SOT23-5L
Pin Number 1 2 3 4
Name EN GND SW VIN VFB
Description Enable Pin. Do not leave the pin floating. VEN<0.4V: Shutdown mode VEN>1.2V: Device enabled Ground Signal Pin. Switching node. Power Supply Pin. Must be decoupled to ground with a 4.7F or greater ceramic capacitor. Adjustable Version Feedback Input Pin. Connect VFB to the center point of the resistor divider. Fixed Output Voltage Version, Output Voltage Pin. An internal resistive divider divides the output voltage down for comparison to the internal reference voltage.
5 VOUT
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 2/10
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground.
Input Voltage VIN ..........................-0.3V to 6V EN VFB Voltage ............................ -0.3V to VIN SW Voltage.................... -0.3V to (VIN + 0.3V) PMOS Switch Source Current (DC) ........ 800mA NMOS Switch Sink Current (DC) ........... 800mA Peak Switch Sink and Source Current ....... 1.3A
Operating Junction Temp. (Note 1)......... 125C Storage Temp. Range TSTG ....... -65C to 150C Lead Temperature (sold. 10s) TLEAD ........ 300C Thermal Resistance RJA ............................................... 250C/W RJC .................................................90C/W
Note 1: TJ is a function of the ambient temperature TA and power dissipation PD (TJ= TA + PD x 250C/W).
Recommended Operating Conditions
Operating Temperature TOP ....... -40C to 85 C Input voltage VIN......................... 2.5V to 5.5V
VIN=3.6V, TA=25C, unless otherwise specified - Boldface characters apply over the full temperature range. Parameter Feedback Current Regulated Feedback Voltage Reference Voltage Line Regulation Output Voltage Accuracy Output Over-Voltage Lockout Output Voltage Line Regulation Peak Inductor Current Output Voltage Load Regulation Quiescent Current (Note 2) Shutdown Current Oscillator Frequency RDS(ON) of PMOS RDS(ON) of NMOS SW Leakage Enable Threshold Shutdown Threshold EN Leakage Current Symbol IVFB VFB VFB VOUT% VOVL VOUT IPK VLOADREG IQ ISHTDWN fosc RPFET RNFET ILSW VEN IEN VFB=0.5V or VOUT=90% VEN=0V, VIN=4.2V VFB=0.6V or VOUT=100% VFB=0V or VOUT=0V ISW=100mA ISW=100mA VEN=0V, VSW=0V or 5V, VIN=5V 0.4 1 1.2 VOVL = VOVL - VFB (Adj.) VOVL = VOVL - VOUT (Fixed) VIN=2.5V to 5.5V VIN=3V, VFB=0.5V or VOUT=90%, Duty cycle <35% 1.0 0.5 200 0.1 1.5 290 0.45 0.40 0.55 0.50 1 1.2 340 1 1.8 TA=25C VIN=2.5V to 5.5V -3 20 2.5 50 7.8 0.588 0.600 Conditions Min Typ. Max 30 0.612 0.4 +3 80 13 0.4 Unit nA V %/V % mV % %/V A % A A MHz kHz A V V A
Note 1: The Switch Current Limit is related to the Duty Cycle. Please refer to figure 15 for details. Note 2: Dynamic quiescent current is higher due to the gate charge being delivered at the switching frequency.
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 3/10
ELECTRICAL CHARACTERISTICS
Typical Characteristics
Fig. 2: Efficiency vs Output Current (mA)
Fig. 3: Efficiency vs Output Current (mA)
Fig. 4: Efficiency vs Output Current (mA)
Fig. 5: Efficiency vs Output Current (mA)
Fig. 6: Output Voltage vs Load Current
Fig. 7: Reference Voltage vs Temperature
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 4/10
ELECTRICAL CHARACTERISTICS
Fig. 8: RDS(ON) vs Temperature
Fig. 9: RDS(ON) vs Input Voltage
Fig. 10: Dynamic Supply Current vs Temperature
Fig. 11: Dynamic Supply Current vs Supply Voltage
Fig. 12: Oscillator Frequency vs Temperature
Fig. 13: Oscillator Frequency vs Supply Voltage
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 5/10
ELECTRICAL CHARACTERISTICS
Fig. 14: Discontinuous Operation
Fig. 15: Start-up from Shutdown
Fig. 16: Load Step
Fig. 17: Load Step
Fig. 17: Load Step
Fig. 18: Load Step
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 6/10
THEORY OF OPERATION
Detailed Description Applications The typical application circuit of the adjustable output voltage option and the fixed output voltage option are shown below. The ESR rating of the capacitor is an important parameter to select COUT. The output ripple VOUT is determined by: Eq. 3: VOUT I L ESR +

1 8 f COUT

Fig. 18: Adjustable Output Voltage Version Typical Application Circuit
Higher values, lower cost ceramic capacitors are now available in smaller sizes. These capacitors have high ripple currents, high voltage ratings and low ESR that makes them ideal for switching regulator applications. As COUT does not affect the internal control loop stability, its value can be optimized to balance very low output ripple and circuit size. It is recommended to use an X5R or X7R rated capacitors which have the best temperature and voltage characteristics of all the ceramics for a given value and size. Output Voltage - Adjustable Version The adjustable output voltage version is determined by: Eq. 4: VOUT = 0.6V 1 + 2 R 1 Thermal Considerations Allthough the SP6669 has an on board over temperature circuitry, the total power dissipation it can support is based on the package thermal capabilities. The formula to ensure safe operation is given in note 1. PCB Layout The following PCB layout guidelines should be taken into account to ensure proper operation and performance of the SP6669: 1- The GND, SW and VIN traces should be kept short, direct and wide. 2- VFB pin must be connected directly to the feedback resistors. The resistor divider network must be connected in parallel to the COUT capacitor. 3- The input capacitor CIN must be kept as close as possible to the VIN pin.
Fig. 19: Fixed Output Voltage Version Typical Application Circuit
Inductor Selection Inductor ripple current and core saturation are two factors considered to select the inductor value. Eq. 1: I L =
R
V 1 VOUT 1 - OUT f L VIN

Equation 1 shows the inductor ripple current as a function of the frequency, and VOUT. It is inductance, VIN recommended to set the ripple current to 40% of the maximum load current. A low ESR inductor is preferred. CIN and COUT Selection A low ESR input capacitor can prevent large voltage transients at VIN. The RMS current rating of the input capacitor is required to be larger than IRMS calculated by: Eq. 2: I RMS I OMAX
VOUT (VIN - VOUT ) VIN
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 7/10
THEORY OF OPERATION
4- The SW and VFB nodes should be kept as separate as possible to minize possible effects from the high frequency and voltage swings of the SW node. 5- The ground plates of CIN and COUT should be kept as close as possible. Ouptut Voltage Ripple for VIN close to VOUT When the input voltage VIN is close to the the SP6669 output voltage VOUT, transitions smoothly from the switching PWM converter mode into a LDO mode. The following diagram shows the output voltage ripple versus the input voltage for a 3.3V output setting and a 200mA current load. Design Example In a single Lithium-Ion battery powered application, the VIN range is about 2.7V to 4.2V. The desired output voltage is 1.8V. The inductor value needed can be calculated using the following equation
L=
V 1 VOUT 1 - OUT f I L VIN

VIN=4.2V, Subsituting VOUT=1.8V, IL=240mA and f=1.5MHz gives
L = 2.86H
A 2.2H inductor can be choosen with this application. An inductor of greater value with less equivalent series resistance would provide better efficiency. The CIN capacitor requires an RMS current rating of at least ILOAD(MAX)/2 and low ESR. In most cases, a ceramic capacitor will satisfy this requirement.
Fig.20: VOUT Ripple Voltage for VIN decreasing close to VOUT
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 8/10
PACKAGE
SOT23-5L Unit: mm
Rev G - 12/02/2008
SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 9/10
ORDERING INFORMATION
Adjustable Output Voltage Version
Part Number SP6669AEK-L/TRR3 "WW" = Work Week Voltage Option Adjustable Operating Temperature Range -40C to +85C Package SOT23-5 Marking QBWW Packing Quantity 3,000/T&R
Fixed Output Voltage Version
Part Number SP6669BEK-L/TRR3 SP6669CEK-L/TRR3 SP6669DEK-L/TRR3 "WW" = Work Week Voltage Option 1.2V 1.5V 1.8V Operating Temperature Range -40C to +85C -40C to +85C -40C to +85C Package SOT23-5 SOT23-5 SOT23-5 Marking RBWW SBWW TBWW Packing Quantity 3,000/T&R 3,000/T&R 3,000/T&R
Note that the SP6669 series is packaged in Tape and Reel with a reverse part orientation as per the following diagram
Notice
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
Exar Corporation Headquarters and Sales Offices 48720 Kato Road Fremont, CA 94538 - USA Tel.: +1 (510) 668-7000 Fax: +1 (510) 668-7030 www.exar.com
Rev G - 12/02/2008 SP6669 1.5MHz 0.6A Sync. Step Down Converter (c) 2008 Exar Corporation 10/10

▲Up To Search▲

Price & Availability of SP6669

	To Download SP6669 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .