 |
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
| Datasheet File OCR Text: |
| LM3350 Switched Capacitor Voltage Converter January 1999 LM3350 Switched Capacitor Voltage Converter General Description The LM3350 is a CMOS charge-pump voltage converter which efficiently provides a 3.3V to 5V step-up, or 5V to 3.3V step-down. The LM3350 uses four small, low cost capacitors to provide the voltage conversion. It eliminates the cost, size and radiated EMI related to inductor based circuits, or the power loss of a linear regulator. Operating power conversion efficiency greater than 90% provides ideal performance for battery powered portable systems. The architecture provides a fixed voltage conversion ratio of 3/2 or 2/3. Thus it can be used for other DC-DC conversions as well. n n n n 4.2 typical step-up output impedance 1.8 typical step-down output impedance 90% typical power conversion efficiency at 50 mA 250 nA typical shutdown current Features n Conversion of 3.3V to 5V, or 5V to 3.3V n Small Mini SO-8 package n No inductor required Applications n n n n Any mixed 5V and 3.3V system Laptop computers and PDAs Handheld instrumentation PCMCIA cards Key Specifications n 800 kHz switch frequency allows use of very small, inexpensive capacitors. Ordering Information Order Number LM3350MMX LM3350MM Package Type Mini SO-8 Mini SO-8 NSC Package Drawing MUA08A MUA08A Package Marking S00A S00A Supplied As 3.5k Units on Tape and Reel 250 Units on Tape and Reel Basic Operating Circuits Step-Up Converter Step-Down Converter DS100002-1 DS100002-2 Connection Diagram Mini SO8 Package DS100002-3 Top View (c) 1999 National Semiconductor Corporation DS100002 www.national.com Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Maximum Input Voltage, Step-Down Maximum Input Voltage, Step-Up Power Dissipation (PD) (TA=25C, (Note 2)) ja (Note 2) Tj Max (Note 2) 5.5V 3.65V 500 mW 250C/W 150C Storage Temperature Lead Temperature (Soldering, 10 secs) ESD Susceptibility (Note 3) Not short circuit protected. -65C to +150C 260C 2kV Operating Conditions (Note 1) Ambient Temperature Range -40C to + 85C Electrical Characteristics 3/2 Step-Up Voltage Converter Specifications in standard type face are for Tj = 25C, and those with boldface type apply over full operating temperature range. Unless otherwise specified, Vin = 3.3V, VEnable = 3.3V, Iload = 50 mA. Symbol VoutNL VoutFL Vin Parameter Output Voltage at No Load Output Voltage at 50 mA Input Supply Voltage Range Quiescent Current Quiescent Current Output Source Impedance Switching Frequency Enable Threshold Voltage Leakage Current Power Efficiency Current into ENABLE pin; ENABLE = 5V and all other pins at ground Shutdown Mode, VEnable = 0V, Iload=0 A; Current into pin Vlow Normal Mode, IIoad = 0A; Current into pin VIow Iload = 50 mA (Note 6) Conditions C1, C2, Cin and Cout: 0.33F, esr 0.33 at 1MHz. Iload = 0 A C1, C2, Cin and Cout: 0.33F, esr 0.33 at 1MHz. Iload = 50 mA Typ (Note 4) 5.0 4.7 3.3 2.5 3.65 IQ1 IQ2 Zout fSW 0.025 3 3.75 5 4.2 6.25 800 500 1100 VEnable 1.7 1.0 2.5 IEnable P 0.025 1 90 Limits (Note 5) Units V V V V(Min) V(Max) A A(Max) mA mA(Max) (Max) kHz kHz(Min) kHz(Max) V V(Min) V(Max) A A(Max) % Electrical Characteristics 2/3 Step-Down Voltage Converter Specifications in standard type face are for Tj = 25C, and those with boldface type apply over full operating temperature range. Unless otherwise specified, Vhigh = 5V, VEnable = 5V, Iload = 50 mA. Symbol VoutNL VoutFL Vin Parameter Output Voltage at No Load Output Voltage at 50 mA Input Supply Voltage Range Quiescent Current Shutdown Mode, VEnable = 0V, Iload=0 A; Current into pin Vhigh 2 Conditions C1, C2, Cin and Cout: 0.33F, esr 0.33 at 1MHz. Iload = 0 A C1, C2, Cin and Cout: 0.33 F, esr 0.33 at 1MHz. Iload =50 mA Typ (Note 4) 3.3 3.2 5 Limits (Note 5) Units V V V 2.2 5.5 0.25 3 V(Min) V(Max) A A(Max) IQ1 www.national.com Electrical Characteristics 2/3 Step-Down Voltage Converter Symbol IQ2 Zout fSW Parameter Quiescent Current Output Source Impedance Switching Frequency Enable Threshold Voltage Leakage Current Power Efficiency (Continued) Specifications in standard type face are for Tj = 25C, and those with boldface type apply over full operating temperature range. Unless otherwise specified, Vhigh = 5V, VEnable = 5V, Iload = 50 mA. Conditions Normal Mode, IIoad = 0A; Current into pin Vhigh Iload = 50 mA (Note 6) Typ (Note 4) 2.5 3.3 1.8 3 800 500 1100 VEnable 1.7 1.0 2.5 IEnable P Current into ENABLE pin; ENABLE = 5V and all other pins at ground 0.025 1 90 Limits (Note 5) Units mA mA(Max) (Max) kHz kHz(Min) kHz(Max) V V(Min) V(Max) A A(Max) % Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test conditions. Note 2: For operation at elevated temperatures, LM3350 must be derated based on package thermal resistance of ja and Tj max, Tj = TA+ jaPD. Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kW resistor into each pin. Note 4: Typical numbers are at 25C and represent the most likely parametric norm. Note 5: Limits are 100% production tested at 25C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. The limits are used to calculate National's Averaging Outgoing Quality Level (AOQL). Note 6: The internal oscillator runs at 1.6 MHz, the output switches operate at one half of the oscillator frequency, fOSC = 2fSW. Typical Performance Characteristics Vout vs Iload (Step-Up) P vs Iload (Step-Up) Output Source Impedance vs Temperature (Step-Up) DS100002-4 DS100002-6 DS100002-9 3 www.national.com Typical Performance Characteristics Vout vs Iload (Step-Down) (Continued) Output Source Impedance vs Temperature (Step-Down) P vs Iload (Step-Down) DS100002-5 DS100002-7 DS100002-8 Switching Frequency vs Temperature DS100002-10 Pin Description Pin 1 2 3 4 5 Name Cap1+ Cap1- Cap2+ Cap2- Vlow Function Positive terminal for the first charge pump capacitor. Negative terminal for the first charge pump capacitor. Positive terminal for the second charge pump capacitor. Negative terminal for the second charge pump capacitor. In Step-Up mode, this will be the input terminal. In Step-Down mode, this will be the output terminal. Ground In Step-Down mode, this will be the input terminal. In Step-Up mode, this will be the output terminal. Active high CMOS logic level Enable Input. Connect to Voltage Input terminal to enable the IC. Connect to Ground (Pin 6) to disable. Detailed Operation OPERATING PRINCIPLE The LM3350 is a charge-pump voltage converter that provides a voltage conversion ratio of 3/2 in step-up mode and a conversion ratio of 2/3 in the step-down mode. Thus it can be used in the step-down mode to provide a 3.3V output from a regulated 5V input or in the step-up mode to provide a 5V output from a regulated 3.3V input. Other values of input voltages can be used as long as they are within the limits. The LM3350 contains an array of CMOS switches which are operated in a certain sequence to provide the step-up or step-down of the input supply. An internal RC oscillator provides the timing signals. Energy transfer and storage are provided by four inexpensive ceramic capacitors. The selection of these capacitors is explained in the Capacitor Selection section under Application Information. 6 7 Gnd Vhigh 8 Enable www.national.com 4 Detailed Operation (Continued) STEP-UP APPLICATIONS NEED AN EXTRA DIODE The LM3350 is biased from pin Vhigh. Thus for step-up applications, an external Schottky diode (D1) is needed to supply power to Vhigh during startup (See Figure 2). Note that during shutdown, this diode will provide a DC path from Vin to Vout. The load may therefore continue to draw current from the input voltage source. This Schottky diode is not required for step-down applications (See Figure 3). SHUTDOWN MODE When ENABLE is a logic low (ground), the LM3350 enters a low power shutdown mode. In this mode, all circuitry is disabled and therefore, all switching action stops. During shutdown, the current consumption drops to 250 nA (typical). When ENABLE is a logic high, (i.e. 3.3V for step-up mode and 5.0V for step-down mode), the LM3350 returns to normal operation. DS100002-11 A. Step-Up Mode Application Information CAPACITOR SELECTION The LM3350 requires four capacitors: an input bypass capacitor (connected between Vin and ground), an output hold capacitor (connected between Vout and ground), and two sampling capacitors (C1 and C2 in Figures 2, 3). 0.33 F (20%) ceramic chip type capacitors are recommended for all four capacitors. The usable operating frequency should be greater than 5 MHz for all capacitors. The input bypass capacitor (Cin) is the least critical. Its value should be at least that of the sampling capacitors. While the recommended sampling capacitor values are 0.33 F, other values may be selected. Values other than 0.33 F affect maximum output current rating and efficiency. Figure 1 shows typical output impedance (Zout) versus capacitor value. The output hold capacitor value determines the output ripple. Increasing the value of the hold capacitor decreases the ripple. The value of this capacitor (Cout) can be calculated (approximately) based on the output ripple (Vout) requirements from: DS100002-12 B. Step-Down Mode FIGURE 1. Zout vs. C PRECAUTIONS The LM3350 is not short circuit protected. where Iload is the load current and fO is the oscillator frequency. In order to ensure superior performance over the entire operating temperature range, capacitors made of X7R dielectric material are suggested. However, capacitors made of other dielectric materials that still meet the 20% specification over the entire temperature range can also be used. 5 www.national.com Typical Application Circuits DS100002-13 FIGURE 2. Step-Up Converter DS100002-14 FIGURE 3. Step-Down Converter Layout Information LAYOUT CONSIDERATIONS The LM3350's high switching frequency (800 kHz) makes a good layout important. Figure 4 illustrates a typical layout. It is important to keep the distance short between the four capacitors and the IC. Wide traces and grounding are also recommended. These steps will minimize trace inductance and high frequency ringing. Of the four capacitors, Chigh and Clow have the highest value of di/dt. It is therefore most important to keep them close to the IC. The ground lead that Chigh and Clow share should also be kept wide and short. The location of the diode (D1) used in the step-up configuration is not critical. This diode is only used during the initial turn on of the IC. D1 is not needed in step-down applications. www.national.com 6 Layout Information (Continued) DS100002-16 B. Actual Size of the Layout DS100002-15 A. Copper side (5X) DS100002-17 C. Copper side with Component Locations (5X) FIGURE 4. Typical Layout 7 www.national.com LM3350 Switched Capacitor Voltage Converter Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead Mini SO (MM) Order Number LM3350MMX or LM3350MM NS Package Number MUA08A LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 2. A critical component in any component of a life support 1. Life support devices or systems are devices or sysdevice or system whose failure to perform can be reatems which, (a) are intended for surgical implant into sonably expected to cause the failure of the life support the body, or (b) support or sustain life, and whose faildevice or system, or to affect its safety or effectiveness. ure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Francais Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: sea.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 www.national.com National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. |
Price & Availability of NSC04920
 |
|
|
|
|
All Rights Reserved © IC-ON-LINE 2003 - 2022 |
| [Add Bookmark] [Contact Us] [Link exchange] [Privacy policy] |
|
Mirror Sites : [www.datasheet.hk]
[www.maxim4u.com] [www.ic-on-line.cn]
[www.ic-on-line.com] [www.ic-on-line.net]
[www.alldatasheet.com.cn]
[www.gdcy.com]
[www.gdcy.net] |