LM3880QMF-1AC

LM3880/LM3880Q Power Sequencer May 1, 2008 LM3880/LM3880Q Power Sequencer General Description The LM3880 Power Sequencer offers the easiest method to control power up and power down of multiple power supplies (switchers or linear regulators). By staggering the startup sequence, it is possible to avoid latch conditions or large in-rush currents that can affect the reliability of the system. Available in a SOT23-6 package, the Power Sequencer contains a precision enable pin and three open drain output flags. Upon enabling the LM3880 the three output flags will sequentially release, after individual time delays, permitting the connected power supplies to startup. The output flags will follow a reverse sequence during power down to avoid latch conditions. EPROM capability allows every delay and sequence to be fully adjustable. Contact National Semiconductor if a nonstandard configuration is required. Features ■ ■ ■ ■ ■ ■ ■ Easiest method to sequence rails Power up and power down control Input voltage range of 2.7V to 5.5V Small footprint SOT23-6 Low quiescent current of 25 µA Standard timing options available Customization of timing and sequence available through factory programmability ■ LM3880Q is AEC-Q100 Grade 1 qualified and is manufactured on an Automotive Grade Flow Applications ■ ■ ■ ■ Multiple supply sequencing Microprocessor / Microcontroller sequencing FPGA sequencing Automotive Typical Application Circuit 20192601 © 2008 National Semiconductor Corporation 201926 www.national.com LM3880/LM3880Q Connection Diagram 20192602 Top View SOT23–6 Package Pin Descriptions Pin # 1 2 3 4 5 6 Name VCC GND EN FLAG3 FLAG2 FLAG1 Function Input supply Ground Precision enable pin Open drain output #3 Open drain output #2 Open drain output #1 Nomenclature 20192603 Sequence Designator Table Sequence Number Power Up 1 2 3 4 5 6 See timing diagrams for more information Flag Order Power Down 3-2-1 3-1-2 2-3-1 2-1-3 1-3-2 1-2-3 1-2-3 1-2-3 1-2-3 1-2-3 1-2-3 1-2-3 www.national.com 2 LM3880/LM3880Q Timing Designator Table Timing Designator AE AA AB AC AD td1 2ms 10ms 30ms 60ms 120ms td2 2ms 10ms 30ms 60ms 120ms td3 2ms 10ms 30ms 60ms 120ms td4 2ms 10ms 30ms 60ms 120ms td5 2ms 10ms 30ms 60ms 120ms td6 2ms 10ms 30ms 60ms 120ms See timing diagrams for more information LM3880 Ordering Information Standard Parts for Order* Order Number LM3880MF-1AE LM3880MFX-1AE LM3880MFE-1AE LM3880MF-1AA LM3880MFX-1AA LM3880MFE-1AA LM3880MF-1AB LM3880MFX-1AB LM3880MFE-1AB LM3880MF-1AC LM3880MFX-1AC LM3880MFE-1AC LM3880MF-1AD LM3880MFX-1AD LM3880MFE-1AD LM3880QMFE-1AE LM3880QMF-1AE LM3880QMFX-1AE LM3880QMFE-1AA LM3880QMF-1AA LM3880QMFX-1AA LM3880QMFE-1AB LM3880QMF-1AB LM3880QMFX-1AB LM3880QMFE-1AC LM3880QMF-1AC LM3880QMFX-1AC LM3880QMFE-1AD LM3880QMF-1AD LM3880QMFX-1AD Timer settings td1 to td6 2ms 2ms 2ms 10ms 10ms 10ms 30ms 30ms 30ms 60ms 60ms 60ms 120ms 120ms 120ms 2ms 2ms 2ms 10ms 10ms 10ms 30ms 30ms 30ms 60ms 60ms 60ms 120ms 120ms 120ms Sequence Order 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Supplied As 1k units T&R 3k units T&R 1k units T&R 3k units T&R 1k units T&R 3k units T&R 1k units T&R 3k units T&R 1k units T&R 3k units T&R Package Type SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 NSC Package Drawing MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A MF06A Package Marking F25A F25A F25A F20A F20A F20A F21A F21A F21A F22A F22A F22A F23A F23A F23A F24A F24A F24A F27A F27A F27A F28A F28A F28A F29A F29A F29A F30A F30A F30A AEC-Q100 Grade 1 qualified. Automotive Grade Production Flow** Feature 250 units T&R SOT23-6 250 units T&R SOT23-6 250 units T&R SOT23-6 250 units T&R SOT23-6 250 units T&R SOT23-6 250 units T&R SOT23-6 1k units T&R 3k units T&R 1k units T&R 3k units T&R 1k units T&R 3k units T&R 1k units T&R 3k units T&R 1k units T&R 3k units T&R SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 250 units T&R SOT23-6 250 units T&R SOT23-6 250 units T&R SOT23-6 250 units T&R SOT23-6 *Non-standard parts are available upon request. Please contact National Semiconductor for more information. **Automotive Grade (Q) product incorporates enhanced manufacturing and support processes for the automotive market, including defect detection methodologies. Reliability qualification is compliant with the requirements and temperature grades defined in the AEC-Q100 standard. Automotive grade products are identified with the letter Q. For more information go to http://www.national.com/automotive. 3 www.national.com LM3880/LM3880Q Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VCC EN, FLAG1, FLAG2, FLAG3 Max Flag 'ON' Current Storage Temperature Range Junction Temperature Lead Temperature (Soldering, 5 sec.) Minimum ESD Rating −0.3V to +6.0V −0.3V to 6.0V 50 mA −65°C to +150°C 150°C 260°C ±2 kV Operating Ratings VCC to GND EN, FLAG1, FLAG2, FLAG3 Junction Temperature (Note 1) 2.7V to 5.5V −0.3V to VCC + 0.3V −40°C to +125°C Electrical Characteristics Specifications with standard typeface are for TJ = 25°C, and those in bold face type apply over the full Operating Temperature Range (TJ = -40°C to +125°C). Minimum and Maximum limits are guaranteed through test, design or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C and are provided for reference purposes only. VCC = 3.3V, and limits apply to all timing options, unless otherwise specified. Symbol IQ Open Drain Flags IFLAG VOL Power Up Sequence td1 td2 td3 Timer delay 1 accuracy 2ms Timing Option Timer delay 2 accuracy 2ms Timing Option Timer delay 3 accuracy 2ms Timing Option Power Down Sequence td4 td5 td6 Timing Delay Error (td(x) – 400 µs) / td(x+1) Ratio of timing delays td(x) / td(x+1) ENABLE Pin VEN IEN EN pin threshold EN pin pull-up current VEN = 0V 1.0 1.25 7 1.4 V µA Ratio of timing delays For x = 1 or 4 For x = 1 or 4, 2ms option For x = 2 or 5 For x = 2 or 5, 2ms option 95 90 95 90 105 110 105 110 % % Timer delay 4 accuracy 2ms Timing Option Timer delay 5 accuracy 2ms Timing Option Timer delay 6 accuracy 2ms Timing Option -15 -20 -15 -20 -15 -20 15 20 15 20 15 20 % % % -15 -20 -15 -20 -15 -20 15 20 15 20 15 20 % % % FLAGx Leakage Current FLAGx Output Voltage Low VFLAGx = 3.3V IFLAGx = 1.2mA 1 20 0.4 nA V Parameter Operating Quiescent current Conditions Min (Note 3) Typ (Note 4) 25 Max (Note 3) 80 Unit µA 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 does not guarantee specific performance limits. For guaranteed specifications and conditions, see the Electrical Characteristics. Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. Note 3: Limits are 100% production tested at 25°. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. The limits are used to calculate National's Average Outgoing Quality Level (AOQL). Note 4: Typical numbers are at 25°C and represent the most likely parametric norm. www.national.com 4 LM3880/LM3880Q Typical Performance Characteristics Quiescent Current vs VCC Quiescent Current vs Temperature (VCC = 3.3V) 20192605 20192604 Enable Threshold vs Temperature Time Delay (30ms) vs VCC 20192606 20192607 Time Delay Ratio vs Temperature Time Delay (30ms) vs Temperature 20192608 20192609 5 www.national.com LM3880/LM3880Q FLAG VOL vs VCC (RFLAG = 100 kΩ) FLAG Voltage vs Current 20192611 20192610 Block Diagram Block Diagram 20192612 www.national.com 6 LM3880/LM3880Q Timing Diagrams (Sequence 1) All standard options use this sequence for output flags rise and fall order. 20192613 Power Up Sequence 20192614 Power Down Sequence Application Information OVERVIEW The LM3880 Power Sequencer provides an easy solution for sequencing multiple rails in a controlled manner. Six independent timers are integrated to control the timing sequence (power up and power down) of three open drain output flags. These flags permit connection to either a shutdown / enable pin of linear regulators and switchers to control the power supplies’ operation. This allows a complete power system to be designed without worrying about large in-rush currents or latch-up conditions that can occur. The timing sequence of the LM3880 is controlled entirely by the enable (EN) pin. Upon power up, all the flags are held low until this precision enable is pulled high. After the EN pin is asserted, the power up sequence will commence. An internal counter will delay the first flag (FLAG1) from rising until a fixed time period has expired. Upon the release of the first flag another timer will begin to delay the release of the second flag (FLAG2). This process repeats until all three flags have sequentially been released. The three timers that control the delays are all independent of each other and can be individually programmed if needed. (See custom sequencer section). The power down sequence is the same as power-up, but in reverse. When EN pin is de-asserted a timer will begin that delays the third flag (FLAG3) from pulling low. The second and first flag will then follow in a sequential manner after their 7 appropriate delays. The three timers that are used to control the power down scheme can also be individually programmed and are completely independent of the power up timers. Additional sequence patterns are also available in addition to customizable timers. For more information see the custom sequencer section. PART OPERATION The timing sequence of the LM3880 is controlled by the assertion of the enable signal. The enable pin is designed with an internal comparator, referenced to a bandgap voltage (1.25V), to provide a precision threshold. This allows a delayed timing to be externally set using a capacitor or to start the sequencing based on a certain event, such as a line voltage reaching 90% of nominal. For an additional delayed sequence from the rail powering VCC, simply attach a capacitor to the EN pin as shown below. www.national.com LM3880/LM3880Q 20192615 Cap Timing Using the internal pull-up current source to charge the external capacitor (CEN) the enable pin delay can be calculated by the equation below: A resistor divider can also be used to enable the LM3880 based on a certain voltage threshold. Care needs to be taken when sizing the resistor divider to include the effects of the internal current source. One of the features of the enable pin is that it provides glitch free operation. The first timer will start counting at a rising threshold, but will always reset if the enable pin is de-asserted before the first output flag is released. This can be shown in the timing diagram below: 20192617 EN Glitch If the enable signal remains high for the entire power-up seWhen this event occurs, the falling edge of enable pin resets quence, then the part will operate as shown in the standard the current timer and will allow the remaining power-up cycle timing diagrams. However, if the enable signal is de-asserted to complete before beginning the power down sequence. The before the power-up sequence is completed the part will enter power down sequence starts approximately 120ms after the a controlled shutdown. This allows the system to walk through final power-up flag. This allows output voltages in the system a controlled power cycling, preventing any latch conditions to stabilize before everything is shutdown. An example of this from occuring. This state only occurs if the enable pin is deoperation can be seen below: asserted after the completion of timer 1, but before the entire power-up sequence is completed. 20192618 Incomplete Sequence All the internal timers are generated by a master clock that mately 400 µs to timers 1 and 4 which is a result of the has an extremely low tempco. This allows for tight accuracy EPROM refresh. This refresh time is in addition to the proacross temperature and a consistent ratio between the indigrammed delay time and will be almost insignificant to all but vidual timers. There is a slight additional delay of approxithe shortest of timer delays. www.national.com 8 LM3880/LM3880Q CUSTOM SEQUENCER The LM3880 Power Sequencer is based on a CMOS process utilizing an EPROM that has the capability to be custom programmed at the factory. Approximately 500,000,000 different options are available allowing even the most complex system to be simply sequenced. Because of the vast options that are possible, customization is limited to orders of a certain quanTimer Options 1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 All times listed are in milliseconds tity. Please contact National Semiconductor for more information. The variables that can be programmed include the six delay timers and the reverse sequence order. For the timers, each can be individually selected from one of the timer selector columns in the table shown below. However, all six time delays must be from the same column. Timer Options 3 0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 Timer Options 4 0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 Timer Options 2 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 The sequencing order for power up is always controlled by layout. The flag number translates directly into the sequence order during power up (ie FLAG1 will always be first). However, for some systems a different power down order could be required. To allow flexibility for this aspect in a design, the Power Sequencer incorporates six different options for controlling the power down sequence. These options can be seen in the timing diagrams on the next page. This ability can be programmed in addition to the custom timers. 9 www.national.com LM3880/LM3880Q 20192619 Power Down Sequence Options www.national.com 10 LM3880/LM3880Q Physical Dimensions inches (millimeters) unless otherwise noted SOT23-6 Package NS Package Number MF06A 11 www.national.com LM3880/LM3880Q Power Sequencer Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Amplifiers Audio Clock Conditioners Data Converters Displays Ethernet Interface LVDS Power Management Switching Regulators LDOs LED Lighting PowerWise Serial Digital Interface (SDI) Temperature Sensors Wireless (PLL/VCO) www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/displays www.national.com/ethernet www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/powerwise www.national.com/sdi www.national.com/tempsensors www.national.com/wireless WEBENCH Analog University App Notes Distributors Green Compliance Packaging Design Support www.national.com/webench www.national.com/AU www.national.com/appnotes www.national.com/contacts www.national.com/quality/green www.national.com/packaging www.national.com/quality www.national.com/refdesigns www.national.com/feedback Quality and Reliability Reference Designs Feedback THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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