LT3582/LT3582-5/LT3582-12 Boost and Single Inductor Inverting DC/DC Converters with Optional I2C Programing and OTP DESCRIPTION FEATURES n n n n n n n n n n Output Voltages: 3.2V to 12.775V and –1.2V to –13.95V (LT3582) 5V and –5V (LT3582-5) 12V and –12V (LT3582-12) Digitally Re-Programmable (LT3582) via I2C for: Output Voltages Power Sequencing Output Voltage Ramp Rates Power-Up Defaults Settable with Non-Volatile OTP (LT3582) I2C Compatible Interface (Standard Mode*) All Power Switches Integrated 350mA Current Limit (Boost) 600mA Current Limit (Inverting) All Feedback Resistors Integrated Input Voltage Range: 2.55V to 5.5V Low Quiescent Current 325μA in Active Mode 0.01μA in Shutdown Mode Integrated Output Disconnect Tiny 16-Pin 3mm × 3mm QFN Package APPLICATIONS n n n AMOLED Power CCD Power General Purpose DC/DC Conversion The LT®3582/LT3582-5/LT3582-12 are dual DC/DC converters featuring positive and negative outputs and integrated feedback resistors. The LT3582, with its built-in One Time Programming (OTP), has configurable output settings via the I2C interface, including output voltage settings, power-up sequencing, power-down discharge, and output voltage ramp rates. LT3582 settings can be changed adaptively in the final product, or set during manufacturing and made permanent using the built in non-volatile OTP memory. The positive output voltage can be set between 3.2V and 12.775V in 25mV steps. The negative output voltage can be set between –1.2V and –13.95V in –50mV steps. The LT3582-5 and LT3582-12 are pre-configured at the factory for ±5V and ±12V outputs respectively, and as such, don’t require the use of the I2C interface. The LT3582 series includes two monolithic converters, one Boost and one Inverting. The Boost converter has an integrated power switch and output disconnect switch. The Inverting converter uses a single inductor topology and includes an integrated power switch. Both Boost and Inverting converters use a novel** control scheme resulting in low output voltage ripple while allowing for high conversion efficiency over a wide load current range. The LT3582 series is available in a 16-pin 3mm × 3mm QFN. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. * Input thresholds are reduced to allow communication with low voltage digital ICs. (See Electrical Characteristics). ** Patent Pending TYPICAL APPLICATION ±12V Supplies from a Single 5V Input SHDN SWN 6.8μH Efficiency and Power Loss 95 VIN SWN INPUT 4.5V TO 5.5V 6.8μH 350 VOUTP VOUTN 300 85 EFFICIENCY (%) GND 4.7μF LT3582 1μF VNEG –12V 85mA I2C INTERFACE OPTIONAL ON LT3582-5/LT3582-12 10μF CAPP VOUTN SDA CAPP VOUTP SCL CA 10nF VPOS 12V 80mA VPP RAMPP RAMPN 10nF 250 75 200 65 150 55 100 45 POWER LOSS (mW) SWP 50 4.7μF 3582512 TA01a 35 0.1 1 10 LOAD CURRENT (mA) 0 100 3582512 TA01b 3582512fb 1 LT3582/LT3582-5/LT3582-12 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) GND VPP SDA SCL TOP VIEW 16 15 14 13 12 SWP CA 1 VOUTN 2 11 CAPP 17 GND SWN 3 10 CAPP SWN 4 6 7 8 RAMPN RAMPP SHDN 9 5 VIN VIN Voltage ..................................................................6V SWP Voltage .............................................................15V SWN Voltage ........................................................ –16.5V CAPP Voltage ............................................................15V CAPP-VOUTP Voltage .................................... –0.8V to 8V ICAPP-VOUTP ....................................................... ±300mA VOUTP Voltage ...........................................................15V VOUTN Voltage ...................................................... –16.5V RAMPP Voltage ..........................................................3V RAMPN Voltage ..........................................................3V SHDN Voltage ................................................ –0.5 to 6V VPP Voltage ...................................................–0.2 to 16V SDA, CA, SCL Voltage .................................... –0.5 to 6V Operating Junction Temperature Range (Notes 3, 5) LT3582E ............................................ –40°C to 125°C Storage Temperature Range .............. –65°C to 150°C VOUTP UD PACKAGE 16-PIN (3mm × 3mm) PLASTIC QFN TJMAX = 125°C, θJA = 68°C/W EXPOSED PAD (PIN #17) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3582EUD#PBF LT3582EUD#TRPBF LDDB 16-Pin (3mm × 3mm) Plastic QFN –40°C to 125°C LT3582EUD-5#PBF LT3582EUD-5#TRPBF LDVG 16-Pin (3mm × 3mm) Plastic QFN –40°C to 125°C LT3582EUD-12#PBF LT3582EUD-12#TRPBF LDVH 16-Pin (3mm × 3mm) Plastic QFN –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, VSHDN = VIN unless otherwise noted. (Note 3) Switching Regulator Characteristics SYMBOL PARAMETER VIN_MIN Minimum Operating Voltage VIN_MAX Maximum Operating Voltage IVIN VIN Quiescent Current IVIN_SHDN CONDITIONS MIN TYP MAX UNITS l 2.4 2.475 2.55 V l 5.5 Ramp Current Configured to 1μA, SWOFF Bit Active 325 450 μA VIN Quiescent Current in Shutdown VSHDN = 0 0.01 0.5 μA ICAPP_SHDN CAPP Quiescent Current in Shutdown VSHDN = 0, VCAPP = 5.0V, VOUTP = 0V 0 0.5 μA TOFF_MINP Minimum Switch Off Time Boost Switch 100 ns TOFF_MINN Minimum Switch Off Time Inverting Switch 125 ns V 3582512fb 2 LT3582/LT3582-5/LT3582-12 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, VSHDN = VIN unless otherwise noted. (Note 3) Switching Regulator Characteristics SYMBOL PARAMETER CONDITIONS MIN TYP MAX TON_MAX Maximum Switch On-Time Inverting and Boost Switches ILIMIT_P Boost Switch Current Limit l 285 350 430 mA ILIMIT_N Inverting Switch Current Limit l 490 600 720 mA 10 UNITS μs RON_P Boost Switch On-Resistance ISWP = 200mA 500 mΩ RON_N Inverting Switch On-Resistance ISWN = –400mA 560 mΩ IOFF_P Boost Switch Leakage Current into SWP Pin VSWP = 5V 0.01 0.5 μA IOFF_N Inverting Switch Leakage Current Out of SWN Pin VIN = 5.0, VSWN = 0.0 0.01 1 μA RON_DIS Output Disconnect Switch On-Resistance VCAPP = 10V, RAMPP > 1.4V 1.4 ILIMIT_DIS Output Disconnect Current Limit 124 155 186 mA IVOUTP_PDS VOUTP Power-Down Discharge Current VOUTP = 8V 2.4 4.8 8.8 mA ICAPP_PDS CAPP Power-Down Discharge Current CAPP = 8V 1.2 2.4 4.4 mA IVOUTN_PDS VOUTN Power-Down Discharge Current VOUTN = –8V –1.4 –2.8 –4.2 mA Configuration Start-Up Delay VIN> VIN_MIN and SHDN > VSHDN_VIH Enabled and Power-Up Sequencing Start 64 128 μs MIN TYP MAX UNITS 4.95 11.88 5 12 5.05 12.1 V V TSTART-UP l to I2C l Ω Programmable Output Characteristics (Note 6) SYMBOL PARAMETER CONDITIONS VVOUTP Positive Output Voltage LT3582-5 LT3582-12 N_VOUTP Positive VOUTP Resolution (Note 2) VVOUTP_LSB VOUTP LSB (Note 2) l l 9 Bits 25 mV VVOUTP_FS VOUTP Full-Scale Voltage (Note 2) Code = BFh, VPLUS = 1 l 12.56 12.775 12.94 V VVOUTP_MIN VOUTP Minimum Voltage (Note 2) Code = 00h, VPLUS = 0 l 3.152 3.20 3.248 V VVOUTP_LR VOUTP Line Regulation Code = BFh, 2.575 < VIN < 5.5 VVOUTN Negative Output Voltage N_VOUTN Negative VOUTN Resolution (Note 2) VVOUTN_LSB VOUTN LSB (Note 2) VVOUTN_FS VOUTN Full-Scale Voltage (Note 2) LT3582-5 LT3582-12 –0.02 l l –5.075 –12.1 –5 –12 %/V –4.925 –11.868 8 Bits –50 mV Code = FFh l –14.2 –13.95 –13.7 l –1.23 –1.205 –1.18 VVOUTN_MIN VOUTN Minimum Voltage (Note 2) Code = 00h VVOUTN_LR VOUTN Line Regulation Code = FFh, 2.575 < VIN < 5.5 V V –0.01 V V %/V INL_VOUTP VOUTP Integral Nonlinearity (Notes 2, 4) l ±0.6 LSB DNL_VOUTP VOUTP Differential Nonlinearity (Notes 2, 4) l ±0.6 LSB INL_VOUTN VOUTN Integral Nonlinearity (Note 2) l ±0.85 LSB DNL_VOUTN VOUTN Differential Nonlinearity (Note 2) l ±0.85 LSB IRAMP00 RAMPP/RAMPN Pull-Up Current IRMP Code = 00 VRAMPP = 0.0V VRAMPN = 0.0V l 0.7 1.0 1.3 μA IRAMP01 RAMPP/RAMPN Pull-Up Current (Note 2) IRMP Code = 01 VRAMPP = 0.0V VRAMPN = 0.0V l 1.4 2.0 2.6 μA 3582512fb 3 LT3582/LT3582-5/LT3582-12 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, VSHDN = VIN unless otherwise noted. (Note 3) Programmable Output Characteristics SYMBOL PARAMETER CONDITIONS IRAMP10 RAMPP/RAMPN Pull-Up Current (Note 2) IRMP Code = 10 VRAMPP = 0.0V VRAMPN = 0.0V IRAMP11 RAMPP/RAMPN Pull-Up Current (Note 2) IRMP Code = 11 VRAMPP = 0.0V VRAMPN = 0.0V VVPLUS VOUTP Voltage Increase When VPLUS Bit is Set from 0 to 1 (Note 2) MIN TYP MAX l 2.8 4.0 5.2 μA l 5.6 8.0 10.4 μA 25 UNITS mV Input/Output Pin Characteristics SYMBOL PARAMETER VSHDN_VIH SHDN Input Voltage High CONDITIONS l MIN VSHDN_VIL SHDN Input Voltage Low l VHYST_SHDN SHDN Input Hysteresis ISHDN_BIAS SHDN Pin Bias Current VCA_VIH CA Input Voltage High l VCA_VIL CA Input Voltage Low l VSDA_VIH SDA Input Voltage High l VSDA_VIL SDA Input Voltage Low l VSCL_VIH SCL Input Voltage High l VSCL_VIL SCL Input Voltage Low l TYP MAX 1.1 V 0.3 50 VSHDN = 1V 2.5 UNITS 4.5 V mV 6.5 0.7 × VIN μA V 0.3 × VIN 1.25 V V 0.85 V 0.85 V 1.25 V VHYST Input Hysteresis SDA, SCL Pins ILEAK_CA CA Input Leakage Current CA = 0V and 5.5V l 80 ±1 mV μA ILEAK_SCL SCL Input Leakage Current SCL = 0V and 5.5V l ±1 μA ILEAK_SDA SDA Input Leakage Current SDA = 0V and 5.5V l ±1 μA CIN Input Capacitance SDA, SCL Pins VSDA_OL SDA Output Low Voltage 3mA into SDA Pin VPP_RANGE VPP Voltage Range for OTP Write (Note 2) VPPUVLO Undervoltage Lockout for VPP Pin (Note 2) 3 l 0.4 13 l pF V 15 V 12.05 12.45 12.85 V MIN TYP MAX UNITS 100 kHz I2C Timing Characteristics SYMBOL PARAMETER fSCL Serial Clock Frequency CONDITIONS l tLOW Serial Clock Low Period l 4.7 μs tHIGH Serial Clock High Period l 4.0 μs tBUF Bus Free Time Between Stop and Start l 4.7 μs tHD,STA Start Condition Hold Time l 4.0 μs tSU,STA Start Condition Setup Time l 4.7 μs tSU,STO Stop Condition Setup Time l 4.0 μs tHD,DATXMIT Data Hold Time Transmitting LT3582 Sending Data to Host l 300 ns tHD,DATRCV Data Hold Time Receiving LT3582 Receiving Data from Host l 0 ns tSU,DAT Data Setup Time l 250 tF SDA Fall Time 400pF Load, VIN ≥ 2.5V l ns 250 ns 3582512fb 4 LT3582/LT3582-5/LT3582-12 ELECTRICAL CHARACTERISTICS Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: LT3582 only. Note 3: The LT3582E is guaranteed to meet performance specifications from 0°C to 125°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlations with statistical process controls. Note 4: These specifications apply to the VP trim bits in REG0 using a 50mV LSB and do not include the additional VPLUS trim bit. See Registers and OTP in the Applications Information section. Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed the maximum operating junction temperature when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 6: Output voltage is measured under non-switching test conditions approximating a moderate load current from the output. 3582512fb 5 LT3582/LT3582-5/LT3582-12 TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequencies (Figure 13) TA = 25°C unless otherwise noted. Load Regulation (Figure 13) Output Voltage (Figure 13) 1.00 10000 0.45 0.75 0.30 0.50 ΔVOUT/VOUT (%) 1000 VOUTN 100 ΔVOUT/VOUT (%) FREQUENCY (kHz) VOUTP 0.25 VOUTP 0 –0.25 VOUTN 0.15 VOUTN 0 VOUTP –0.15 –0.50 –0.30 –0.75 –1.00 10 20 40 60 80 LOAD CURRENT (mA) 0 100 20 40 60 80 LOAD CURRENT (mA) 370 0.6 310 290 270 2.5 125 Switch Current Limit 700 VOUTN 0.5 VOUTP 0.4 0.3 0.2 3 3.5 4 4.5 5 SWN 600 500 400 SWP 300 2.5 3 3.5 4 4.5 INPUT VOLTAGE (V) 3582512 G04 PMOS CURRENT LIMIT (mA) VP CODE SET TO 12V VP CODE SET TO 5V 0 VN CODE SET TO –5V –20 VN CODE SET TO –12V –40 –60 CURRENT OUT OF VOUTN PIN –80 0 2.5 5 7.5 10 |VOUT| (V) 12.5 15 3582512 G07 –25 0 25 50 75 TEMPERATURE (°C) 100 Output Disconnect PMOS On-Resistance 200 2.5 180 2 160 140 120 100 –50 125 3582512 G06 ON-RESISTANCE (Ω) CURRENT INTO VOUTP PIN 20 5.5 Output Disconnect PMOS Current Limit During Normal Operation 80 40 5 3582512 G05 VOUTP and VOUTN Pin Current During Normal Operation 60 200 –50 0 5.5 VIN (V) PIN CURRENT (μA) 100 0.1 250 –100 0 25 50 75 TEMPERATURE (°C) 3582512 G03 Switch Resistance O.7 SWITCH RESISTANCE (Ω) QUIESCENT CURRENT (μA) Quiescent Current – Not Switching 390 330 –25 3582512 G02 3582512 G01 350 –0.45 –50 100 SWITCH CURRENT LIMIT (mA) 0 1.5 1 0.5 –25 0 25 50 75 TEMPERATURE (°C) 100 125 3582512 G08 0 2 4 6 8 VCAPP (V) 10 12 3582512 G09 3582512fb 6 LT3582/LT3582-5/LT3582-12 TYPICAL PERFORMANCE CHARACTERISTICS Note: All waveforms on this page apply to Figure 13. Switching Waveform at 1mA Load (Boost) Switching Waveform at 100mA Load (Boost) Switching Waveform at 10mA Load (Boost) VSWP 5V/DIV VSWP 5V/DIV VSWP 5V/DIV VVOUTP 10mV/DIV AC COUPLED VVOUTP 10mV/DIV AC COUPLED VVOUTP 10mV/DIV AC COUPLED IL2 0.2A/DIV IL2 0.2A/DIV IL2 0.2A/DIV 5μs/DIV 3582512 G10 2μs/DIV Switching Waveform at 1mA Load (Inverting) VSWN 10V/DIV VVOUTN 0.1V/DIV AC COUPLED VVOUTN 50mV/DIV AC COUPLED LOAD CURRENT –20mA/DIV IL1 0.2A/DIV IL1 0.2A/DIV 5μs/DIV 3582512 G13 VOUTP 0.2V/DIV AC COUPLED IL1 0.2A/DIV 5μs/DIV Load Transient, VOUTP, 30mA to 60mA to 30mA Steps 50μs/DIV 3582512 G14 3582512 G15 Power-Down Discharge Waveforms (PUSEQ = 11, PDDIS = 1) Power-Up Sequencing Waveforms (PUSEQ = 11) VRAMPN 1V/DIV VRAMPP 1V/DIV VRAMPN 1V/DIV LOAD CURRENT 20mA/DIV 3582512 G12 Load Transient, VOUTN, 30mA to 60mA to 30mA Steps Switching Waveform at 10mA Load (Inverting) VSWN 10V/DIV VVOUTN 20mV/DIV AC COUPLED 200ns/DIV 3582512 G11 VRAMPP 1V/DIV VVOUTP 5V/DIV VVOUTP 5V/DIV IL2 0.2A/DIV VVOUTN 5V/DIV 50μs/DIV 3582512 G16 VVOUTN 5V/DIV 5ms/DIV 3582512 G17 5ms/DIV 3582512 G18 3582512fb 7 LT3582/LT3582-5/LT3582-12 PIN FUNCTIONS CA (Pin 1): I2C Address Select Pin. Tie this pin to VIN to set the 7-bit address to 0110 001. Tie to GND for 1000 101. VOUTN (Pin 2): Negative Output Voltage Pin. When the converter is operating, this pin is regulated to the programmed negative output voltage. Place a ceramic capacitor from this pin to GND. SWN (Pins 3, 4): Negative Switching Node for the Inverting Converter. This is the drain of the internal PMOS power switch. Connect one end of the Inverting inductor to these pins. Keep the trace area on these pins as small as possible. VIN (Pin 5): Input Supply Pin and Source of the PMOS Power Switch. This pin must be bypassed locally with a ceramic capacitor. The operating voltage range of this pin is 2.55V to 5.5V. RAMPN (Pin 6): Soft-Start Ramp Pin for the Inverting Converter. Place a capacitor from this pin to GND. A programmable current of 1μA to 8μA (LT3582) or 1μA (LT3582-5/LT3582-12) charges this pin during start-up, limiting the ramp rate of VOUTN. This pin is discharged to GND during shutdown. RAMPP (Pin 7): Soft-Start Ramp Pin for the Boost Converter. Place a capacitor from this pin to GND. A programmable current of 1μA to 8μA (LT3582) or 1μA (LT3582-5/LT3582-12) charges this pin during start-up, limiting the ramp rate of VOUTP. This pin is discharged to GND in shutdown. SHDN (Pin 8): Shutdown Pin. Drive this pin to 1.1V or higher to enable the part. Drive to 0.3V or lower to shut down. Includes an integrated 222k pull-down resistor. CAPP (Pins 10, 11): Connect the Boost output capacitor from these pins to GND. During shutdown, the voltage on these pins will remain close to the input voltage due to the path through the Boost inductor and Schottky. During normal operation, CAPP will be boosted slightly higher than the programmed output voltage. SWP (Pin 12): Positive Switching Node for the Boost Converter. This is the drain of the internal NMOS power switch. Connect one end of the Boost inductor to this pin. Keep the trace area on this pin as small as possible. GND (Pin 13): Ground Pin. Tie to a local ground plane. Proper PCB layout is required to achieve advertised performance; see the Applications Information section for more information. VPP (Pin 14): Programming Voltage Pin. Drive this pin to 13-15V when programming the OTP memory. Float otherwise. A bypass capacitor should be placed from this node to GND if VPP is used for programming. If VPP falls below 13V during OTP programming, an internal FAULT bit, which can be read through the I2C interface, can be set high. SDA (Pin 15): I2C Bidirectional Data Pin. Tie to GND or VIN if unused. SCL (Pin 16): I2C Clock Pin. Tie to GND or VIN if unused. Exposed Pad (Pin 17): Ground Pin. Tie to a local ground plane. Proper PCB layout is required to achieve advertised performance; see the Applications Information section for more information. VOUTP (Pin 9): Output of the Boost Converter Output Disconnect Circuit. A ceramic capacitor should be placed from this node to GND. During shutdown, this pin is disconnected from the Boost network which allows this pin to discharge to GND, assuming a load is present to discharge the capacitance. 3582512fb 8 LT3582/LT3582-5/LT3582-12 BLOCK DIAGRAM SWP VIN Q S Q R VARIABLE DELAY VARIABLE DELAY S Q R Q CAPP CAPP VOUTP DISCONNECT CONTROL – + SWN – + SWN IPEAK TOFF CONTROL – IPEAK TOFF CONTROL + VOUTN VCN FBN OTP + + – 2V VCP GND – – + + – OTP + + FBP 0.80V SHDN CHIP ENABLE 222k VIN VPP 0.80V SCL VIN OTP ADJUST CAPP VOUTP SERIAL INTERFACE, LOGIC AND OTP SDA RAMPN OUTPUT SEQUENCING BY OTP 2V + – + – 0.75V CA FBP FBN VOUTN 3582512 BD 50mV OUTPUT SEQUENCING OTP ADJUST RAMPP 3582512fb 9 LT3582/LT3582-5/LT3582-12 OPERATION The LT3582 series are dual DC/DC converters, each containing both a Boost and an Inverting converter. Operation can be best understood by referring to the Block Diagram. The Boost and Inverting converters each use a novel control technique, which simultaneously varies both peak inductor current and switch off time. This results in high efficiency over a large load range and low output voltage ripple. In addition, this technique further minimizes output ripple when the switching frequency is in the audio band. Boost Converter: The Boost converter uses a grounded source NMOS power transistor as the main switching element. The current in the NMOS is constantly monitored and controlled, along with the off-time of the switch to achieve regulation of VOUTP. The VOUTP voltage is divided by the internal programmable (LT3582 only) resistor divider to create FBP. The voltage on FBP is compared to an internal reference and amplified, creating an error signal on the VCP node which commands the appropriate peak inductor current and off time for the subsequent switching cycle. Inverting Converter: The Inverting converter uses a power PMOS transistor with the source connected to VIN. This topology requires only one external inductor, instead of the normally required two inductors plus flying capacitor. Regulation is achieved in a similar manner as the Boost. Output Power-Up Sequencing: After an initial start-up delay (TSTART-UP = 64μs typical), the outputs VOUTP and VOUTN rise (in magnitude) simultaneously with the LT3582-5/ LT3582-12 or in one of four selectable sequences with the LT3582. Using the I2C interface, the LT3582 outputs can be configured such that (1) they both rise simultaneously, (2) VOUTP rises to regulation before VOUTN rises, (3) VOUTN rises to regulation before VOUTP rises, or (4) neither output rises. The outputs of the LT3582-5 and LT3582-12 are pre-configured to rise simultaneously. The ramp rates of the outputs are proportional to the ramp rates of their respective RAMP pins. A capacitor is placed between each RAMP pin and ground. The RAMP pins are discharged during shutdown. Once enabled, configurable (LT3582) or pre-configured (LT3582-5/LT3582-12) currents charge each RAMP pin in the desired sequence causing the outputs to rise. Output Power-Down Discharge: The power-down discharge feature is permanently enabled on the LT3582-5 and LT3582-12 and can be enabled or disabled through I2C on the LT3582. Upon SHDN falling, and when powerdown discharge is enabled, internal transistors will activate to assist in discharging the outputs toward ground. When power-down discharge is disabled, the chip powers down immediately after SHDN falls and the outputs will discharge on their own depending on their external load capacitances and currents. OTP Memory (LT3582 Only): The LT3582 includes 22 bits of user programmable output settings and 1 programming lockout bit. Parameters such as positive and negative output voltages and power sequencing settings can be changed in real time with the integrated I2C interface. Settings can then be made permanent by programming to the on-chip non-volatile OTP (One Time Programmable) memory. 3582512fb 10 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION I2C Interface ACKnowledge The LT3582 series contains an I2C compatible interface allowing it to be digitally configured. The use of this interface is optional for the LT3582-5 and LT3582-12 as these parts are pre-configured at the factory. The CA, SDA and SCL pins can be grounded if the I2C interface is unused. The acknowledge signal (ACK) is used in handshaking between transmitter and receiver to indicate that the most recent byte of data was received. The transmitter always releases the SDA line during the acknowledge clock pulse. When the slave is the receiver, it pulls down the SDA line so that it remains LOW during this pulse to acknowledge receipt of the data. If the slave fails to acknowledge by leaving SDA high, then the master may abort the transmission by generating a STOP condition. When the master is receiving data from the slave, the master pulls down the SDA line during the clock pulse to indicate receipt of the data. After the last byte has been received the master leaves the SDA line HIGH (not acknowledge) and issues a stop condition to terminate the transmission. The I2C interface has reduced input threshold voltages to allow for direct communication with low voltage digital ICs (see Electrical Characteristics). I2C communication is disabled when SHDN is low. After SHDN rises, I2C communication is re-enabled after a delay of 64μs (typical). The chip is a read-write slave device which allows the user to read the current settings and, for the LT3582, write new ones. Most settings can be made permanent via the One-Time-Programmable memory. The chip will always enable using the data stored in OTP and the LT3582 can be reconfigured after power-up. Device Addressing The LT3582 series supports two 7-bit chip addresses depending on the logic state of the CA pin. The addresses are 0110 001 (CA = 1) and 1000 101 (CA = 0). Also, there are seven internal data byte locations as shown in Table 1. OTP0-OTP2 are the OTP memory bytes. REG0-REG2 are the corresponding volatile registers used for storing alternate settings. Finally, the Command Register (CMDR) is used for additional control of the chip. START and STOP Conditions When the bus is idle, both SCL and SDA are high. A bus master signals the beginning of a transmission with a START condition by transitioning SDA from high to low while SCL is high, as shown in Figure 1. When the master has finished communicating with the slave, it issues a STOP condition by transitioning SDA from low to high while SCL is high. The bus is then free for another transmission. SDA A6 - A0 SCL 1-7 B7 - B0 8 9 1-7 B7 - B0 8 9 1-7 8 9 S START CONDITION P CHIP ADDRESS R/W ACK DATA ACK DATA ACK STOP CONDITION 3582512 F01 Figure 1. Data Transfer Over I2C Bus 3582512fb 11 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION All data bytes can be read from their assigned register addresses. Since they share the same register addresses, reads of the OTP and REG data bytes are differentiated by their corresponding RSEL (Register Select) bits in the CMDR register. All data written to register addresses 0-2 is stored in REGO-REG2. Regardless of the RSEL bits, OTP bytes cannot be written directly. See the OTP Programming section for more information. Data Transfer Protocol The LT3582 series supports 8-bit data transfers in the transaction formats shown in Figures 2 and 3. Multiple data bytes can only be transferred by issuing multiple transactions. Figure 2 shows the required format for writing a byte of data to the LT3582 series. Again, the chip address depends on the CA pin logic state. S CHIP ADDR W A REG ADDR A DATA A 0110 001 OR 1000 101 0 0 00000b2:b0 0 b7:b0 0 FROM MASTER TO SLAVE FROM SLAVE TO MASTER P A: ACKNOWLEDGE (LOW) A: NOT ACKNOWLEDGE (HIGH) R: READ BIT (HIGH) W WRITE BIT (LOW) S: START CONDITION P: STOP CONDITION Figure 2. I2C Byte Write Transaction A byte of data is read from the LT3582 series using the format shown in Figure 3. This transaction requires four I2C bytes to read one byte of chip data and must be repeated for each subsequent byte of data that is read. S CHIP ADDR W A REG ADDR A 0110 001 OR 1000 101 0 0 00000b2:b0 0 S CHIP ADDR R A DATA A 0110 001 OR 1000 101 1 0 b7:b0 1 Figure 3. I2C Byte Read Transaction P LT3582 Chip Configuration Settings such as output voltages and sequencing are digitally programmable. The chip uses settings from either the REG or OTP bytes, depending on the states of the corresponding RSEL bits (0 for OTP and 1 for REG). During shutdown the RSEL bits are reset low. As a result, the initial configuration comes from the OTP data bytes. After power-up, the configuration can be changed by writing new settings to the appropriate REG data byte(s) then setting the corresponding RSEL bit(s). Finally, data in the REG bytes can be permanently programmed to OTP by applying voltage to the VPP pin and setting the WOTP bit in the Command Register. See the OTP Programming section for more information. LT3582-5/LT3582-12 Chip Configuration The LT3582-5/LT3582-12 are shipped from the factory with the OTP memory pre-programmed and LOCKed which prohibits subsequent changes to the configuration. The configuration can still be read through the I2C bus and the RST and SWOFF bits of the CMDR register (described later) are functional. The following sections describe the various configurable features of the LT3582. The LT3582-5 and LT3582-12 are pre-configured as follows: VP and VN are programmed for ±5V or ±12V respectively, LOCK = 1, IRMP = 00, PDDIS = 1, PUSEQ = 11 and VPLUS may be 1 or 0. Since LOCK = 1, subsequent configuration changes are prohibited. See Configuration Lockout (LOCK Bit) for more information. Registers and OTP The registers and OTP bytes for the LT3582 series are organized as shown in Table 1. The CMDR is reset to 00h upon power-up, during shutdown and during undervoltage and thermal lockouts. REG0-REG2 are never reset and must always be loaded with valid data before use. The LT3582’s OTP memory is shipped with all 0’s, and as a result, the PUSEQ bits are configured to disable the outputs. The PUSEQ bits must be reconfigured to enable the outputs. 3582512fb 12 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION CMDR: The Command Register is used to control various functions of the chip. During shutdown and power-up the CMDR is initialized to 00h. The RSEL (Register Select) bits are functional only for the LT3582. The LT3582-5 and LT3582-12 function as if the RSEL bits are always “0”. These bits perform three functions: • Each RSEL bit instructs the chip whether to use the configuration data from the corresponding OTP byte (RSELx = 0) or the REG byte (RSELx = 1). Changing an RSELx bit immediately updates the chip configuration. Table 1: LT3582 Series Register Map REGISTER REGISADDRESS TER NAME BIT DESCRIPTION NAME 00h REG0/ OTP0 7:0 VP VOUTP Output Voltage (00h=3.2V, BFh = 12.75V) 01h REG1/ OTP1 7:0 VN VOUTN Output Voltage (00h=1.2V, FFh = 13.95V) 7 - 6 LOCK Lockout Bit: See the OTP Programming Lockout Section. 5 VPLUS VOUTP Output Voltage Bit: Increase VOUTP by ~25mV 4:3 IRMP RAMPP and RAMPN Pull-Up Current: IRAMP = (2) IRMP μA 02h REG2/ OTP2 • Each RSEL bit determines if I2C reads return data from the corresponding OTP byte (RSELx = 0) or the REG byte (RSELx = 1). 2 Reserved, Write to 0 PDDIS Power-Down Discharge Enable. PUSEQ Must be 11 if Set. 1:0 PUSEQ Power-Up Sequencing: 00 = Outputs Disabled, 01 = VOUTN Ramp 1st, 10 = VOUTP Ramp 1st, 11 = Both Ramp Together • OTP programming only programs data to the bytes with corresponding RSEL bits set high. Setting the SWOFF bit immediately disables the Boost and Inverting power switches and opens the output disconnect PMOS switch. It is recommended to set this bit before writing new configuration data. This can prevent unexpected chip behavior while modifying the configuration and also forces a soft-start after SWOFF is cleared (see Soft-Start and Power-Up Sequencing). Writing “1” to the RST bit resets the internal I2C logic and the CMDR register. Reading bit 6 of the CMDR returns the FAULT bit indicating if an OTP programming attempt may have failed. FAULT is cleared during reset, power-up, or by writing a “1” to the CF (Clear Fault) bit. Conditions that set the FAULT bit are (1) OTP programming in which the VPP voltage is too low or (2) attempted OTP programming when the LOCK bit is set. OTP write attempts that set the FAULT bit due to low VPP voltage should be considered failures and the device should be discarded. Attempts to re-program the OTP memory after the FAULT bit has been set are not recommended. Finally, setting the WOTP bit starts the OTP programming. BIT 7 WOTP Write OTP Memory 6 CF/ Clear Fault/OTP Programming FAULT Fault 5 4 04h CMDR 3 RST Reset SWOFF Switches-Off - Reserved, Write to 0 2 RSEL2 Register Select 2 (0 = OTP2, 1 = REG2) 1 RSEL1 Register Select 1 (0 = OTP1, 1 = REG1) 0 RSEL0 Register Select 0 (0 = OTP0, 1 = REG0) OTP0/REG0 and OTP1/REG1: Data in addresses 00h and 01h is used to set the output voltages of the Boost and Inverting converters respectively. See Setting the Output Voltages for more information. 3582512fb 13 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION OTP2/REG2: Data in address 02h configures the output voltage sequencing, sets a fine voltage adjust for VOUTP, and determines if further OTP programming is permitted or not. Proper uses of the bits in address 02h are discussed in the following sections. Setting the Output Voltages (VP , VPLUS and VN Bits) The LT3582 series contains two resistor dividers which are programmable in the LT3582, to set the output voltages. The positive output voltage VOUTP is adjustable in 25mV steps by setting the VP bits in REG0/OTP0 in addition to the VPLUS bit in REG2/OTP2. VOUTP = 3.2V + (VP • 50mV) + (VPLUS • 25mV) where: VP = an integer value from 0 to 191 VPLUS = 0 or 1 The VOUTN voltage is adjustable in –50mV steps by setting the VN bits in REG1/OTP1. VOUTN = –1.2V – (VN • 50mV) where: VN = an integer value from 0 to 255 Dynamically Changing the Output Voltage (LT3582 Only): After output regulation has been reached, it’s possible to change the output voltages by writing new values to the VN or VP bits. When reducing the magnitude of an output voltage, it will decay at a rate dependent on the load current and capacitance. Configuring a large increase in magnitude of an output voltage can cause a large increase in switch current to charge the output capacitor. Before reconfiguring the outputs, consider forcing a soft-start by asserting the SWOFF bit before writing the new VP or VN codes. Subsequently clearing SWOFF initiates the new soft-start sequence. Soft-Start/Output Voltage Ramping (IRMP Bits) The LT3582 series contains soft-start circuitry to control the output voltage ramp rates, therefore limiting peak switch currents during start-up. High switch currents are inherent in switching regulators during start-up since the feedback loop is saturated due to VOUT being far from its final value. The regulator tries to charge the output capacitor as quickly as possible which results in large currents. Capacitors must be connected from RAMPP and RAMPN to ground for soft-start. During shutdown or when the SWOFF bit is set, the RAMP capacitors are discharged to ground. After SHDN rises or SWOFF is cleared, the capacitors are charged by programmable (LT3582 only) currents, thus creating linear voltage ramps. The VOUT voltages ramp in proportion to their respective RAMP voltages according to: ⎞ ⎛V ⎞ ⎛ I VOUT _RAMP _RATE = ⎜ OUT ⎟ • ⎜ RAMP ⎟ Volts / Sec ⎝ 0.8V ⎠ ⎝ CRAMP ⎠ Proportionality Constant RAMP pin ramp rate (V/Sec) where: IRAMP = RAMP pin charging current set by IRMP bits (1μA, 2μA, 4μA or 8μA for LT3582, 1μA for LT3582-5/LT3582-12) CRAMP = External RAMP pin capacitor (Farads) VOUT = Output voltage during regulation For example, selecting IRAMP = 1μA, CRAMP = 10nF and VOUTP = 12V results in a power-up ramp rate of 1.5Volt/ms (see Figure 6). Ramp rates less than 1-10V/ms generally result in good start-up characteristics. The outputs should linearly follow the RAMPx voltages with no distortions. Figure 7 shows an excessive start-up ramp rate of ~120V/ms in which 3582512fb 14 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION several start-up issues have occurred: A) the expected VOUTP ramp up path is not followed B) inductor current ringing occurs C) the VOUTP ramp rate is limited due to the output disconnect current limit being reached D) additional ringing occurs when the CAPP pin starts charging E) output voltage overshoot occurs because the inductor currents are maximized during the output ramp-up. The LT3582 series incorporates an output disconnect PMOS allowing VOUTP to be grounded during shutdown. Once enabled, the Disconnect Control circuit actively drives the PMOS gate allowing VOUTP to ramp up linearly as shown in Figure 6. Once VOUTP reaches regulation, the PMOS is fully turned “on” to reduce resistance and improve efficiency. In some cases it may be desirable to use only one RAMP pin capacitor. In cases where PUSEQ = 11 (see the PowerUp Sequencing section) the RAMPP and RAMPN pins can be connected together and to a single capacitor. In this case the capacitor will charge with twice the current configured by the IRMP bits. Power-Up Sequencing (PUSEQ bits) Ramping VOUTP from Ground: The LT3582 series has the unique ability to generate a smooth VOUTP voltage ramp starting from ground and continuing all the way up to regulation (see Figure 6). This ability is not possible with typical Boost converters in which the output is taken from the cathode of the Schottky diode (CAPP node in Figure 5). Once enabled, the part requires a delay of TSTART-UP (64μs typ) to properly configure itself. Once configured, the order in which VOUTP and VOUTN ramp to regulation is controlled by the PUSEQ bits. The combinations available for the LT3582 are shown in Table 2. The LT3582-5/LT3582-12 are pre-configured with the 11 combination. Table 2. Power-Up Sequences PUSEQ[1:0] Power-Up Sequence 00 Outputs are disabled, neither output ramps up 01 VOUTN ramps up 1st, followed by VOUTP 10 VOUTP ramps up 1st, followed by VOUTN 11 Both VOUTP and VOUTN ramp-up starting at the same time. L1 SWP D1 LT3582 SERIES CAPP VOUTP C1 C2 VIN C3 DISCONNECT CONTROL Selecting the 01 or 10 combinations cause one of the outputs to start ramping shortly after SHDN rises. The ramp rate of VOUT is controlled by the RAMP pin as discussed in the Soft-Start section. After VOUT nears its target regula- LOAD A 3582512 F05 Figure 5. Boost Converter Topology E VRAMPP 0.5V/DIV CAPP 3V/DIV B D VOUTP 3V/DIV C IL2 0.2A/DIV CAPP 2V/DIV 50μs/DIV VOUTP 2V/DIV VRAMPP 0.2V/DIV IL2 0.2A/DIV 3582512 F07 Figure 7. VOUTP Soft-Start with Excessive Ramp Rate 1ms/DIV 3582512 F06 Figure 6. VOUTP Soft-Start Ramping from Ground 3582512fb 15 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION tion voltage, the remaining output is activated and ramps under control of its respective RAMP pin (see Figure 8). The power-up sequencing concludes when both outputs have reached regulation. Evaluating PUSEQ Settings (LT3582 Only): After SHDN rises, the LT3582 uses the PUSEQ configuration found in OTP. The effects of differing PUSEQ settings can be observed without writing to OTP by taking the following actions: The PDDIS bit must only be set in conjunction with PUSEQ being set to 11. Driving SHDN low, with powerdown discharge enabled (PDDIS = 1) causes the chip to power-down after first discharging the output voltages. Specifically, driving SHDN low causes the following sequence of events to happen: 1. Both converters are turned off. 2. Discharge currents are enabled to discharge the output capacitors 1. Write the SWOFF bit high, stopping both converters and discharging the RAMP pins. • See Electrical Characteristics for IVOUTP-PDS and ICAPP-PDS which help discharge VOUTP and CAPP 2. Write the desired settings to the PUSEQ bits in REG2. 3. Set the RSEL2 bit high which selects the REG2 configuration settings. • See Electrical Characteristics for IVOUTN-PDS which helps discharge VOUTN 4. Write SWOFF low which restarts both converters. 3. The chip waits until the output voltages have discharged to within ~0.5V to ~1.5V of ground. This will initiate the desired power-up sequence that can be observed with an oscilloscope. 4. Discharge currents are disabled and the LT3582 powers down. Power-Down Discharge (PDDIS bit) Since the LT3582 series won’t power-down until both outputs are discharged (when power-down sequencing is enabled), make sure VOUTP and VOUTN can be grounded. This is not a problem in most topologies. However, read the section Output Disconnect Operating Limits for additional information. The PDDIS bit is used to enable power-down discharge. This bit is pre-configured to a “1” for the LT3582-5 and LT3582-12, thus enabling power-down discharge.Setting PDDIS = 0 disables the power-down discharge causing the chip to shut down immediately after SHDN falls. RAMPP VRAMPP 0.5V/DIV VRAMPN 0.5V/DIV RAMPN VVOUTP 5V/DIV VVOUTN 5V/DIV 5ms/DIV 3582512 F08 Figure 8. Power-Up Sequencing (PUSEQ = 10) 3582512fb 16 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION Configuration Lockout (LOCK bit) After a desired configuration is programmed into OTP, the LOCK bit can be set to prohibit subsequent changes to the configuration. The LT3582-5 and LT3582-12 are preconfigured with the LOCK bit set to a logic “1” which: • Forces the chip to use the OTP configuration only. • Forces all I2C reads from addresses 0-2 to return OTP data. • Prohibits any further programming of the OTP memory. Any further attempts to program OTP leaves the OTP memory unchanged and sets the FAULT bit in the CMDR. The LOCK OTP bit is set by programming a logic “1” into bit 6 of OTP2. Regardless of the RSEL2 setting, I2C reads of the LOCK bit always indicate the LOCKed or unlocked state of the OTP memory. OTP Programming (LT3582 only) The LT3582 contains One Time Programmable non-volatile memory to permanently store the chip configuration. Before programming, it’s recommended to set the SWOFF bit to disable switching activity and prevent unexpected chip behavior while the configuration is being changed. Programming involves the transfer of information from the REG bytes to the OTP bytes. Therefore, valid data must first be written to the desired REG bytes. After the REG bytes are written, they are selected by setting the corresponding RSEL bits in the CMDR. This forces the chip into the desired configuration and selects those bytes for programming to OTP. After 15V has been applied to VPP, the WOTP bit is set in the CMDR to start the programming. Finally, the WOTP bit is cleared to finish the programming. An example programming algorithm is given below. OTP programming draws about 3mA to 6mA per bit from the VPP pin. It is possible to program all 23 bits simultaneously (up to ~138mA), but it is recommended that one byte is programmed at a time to reduce noise on VPP caused by the sudden change in current. A 1-10μF VPP bypass capacitor is also recommended to prevent voltage droop after programming begins. Also, avoid hot-plugging VPP which results in very fast voltage ramp rates and can lead to excessive voltage on the VPP pin. Example OTP Programming Algorithm: 1. Apply 15V to the VP-P pin. This can be done at any time before step 5. 2. Write 50h to the CMDR. This disables the power switches during programming by setting the SWOFF bit in the CMDR. This also clears the FAULT bit. 3. Write desired data to REG0-REG2. 4. Write 11h to the CMDR. This selects REG0 for programming while keeping the switches off. 5. Write 91h to the CMDR. This programs the REG0 data to OTP0. 6. Write 11h to the CMDR. This command can be sent immediately after step 5. This stops the programming. 7. Read the CMDR and verify that the FAULT bit is not set. 8. Repeat steps 4-7 for the remaining bytes that need programming. 9. Write 10h to the CMDR. This selects the OTP data for read verification. 10. Read the OTP data and verify the contents. 11. Write 00h to CMDR. This enables the power switches and the chip will operate from the OTP configuration. 12. Float the VPP pin. This can be done at any time after step 8. 3582512fb 17 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION Choosing Inductors Several series of inductors that work well with the LT3582 series are listed in Table 3. This table is not complete, and there are many other manufacturers and parts that can be used. Consult each manufacturer for more detailed information and for their entire selection of related parts, as many different sizes and shapes are available. Table 3. Inductor Manufacturers Peak Current Rating: Real inductors can experience a drop in inductance as current and temperature increase. The inductors should have saturation current ratings higher than the peak inductor currents. The peak inductor currents can be calculated as: IPK ≅ILIMIT + VLSWON • TOS mA L where: Coilcraft LPS3008-LPS4018 Series, XPL2010 Series www.coilcraft.com Murata LQH32C, LQH43C Series www.murata.com Sumida CDRH26D09, CDRH26D11, www.sumida.com CDRH3D14 Series TDK VLF and VLCF Series www.tdk.com Würth Elektronik WE-TPC Series Type T, TH, XS and S www.we-online.com Inductances of 2.2μH to 10μH typically result in a good tradeoff between inductor size and system performance. More inductance typically yields an increase in efficiency at the expense of increased output ripple. Less inductance may be used in a given application depending on required efficiency and output current. For higher efficiency, choose inductors with high frequency core material, such as ferrite, to reduce core losses. Also to improve efficiency, choose inductors with more volume for a given inductance. The inductor should have low DCR (copper-wire resistance) to reduce I2R losses, and must be able to handle the peak inductor current without saturating. To minimize radiated noise, use a toroidal or shielded inductor (note that the inductance of shielded types will drop more as current increases, and will saturate more easily). IPK ILIMIT L VLSWON TOS = Peak inductor current = Typically 350mA for Boost and 600mA for Inverting = Inductance in μH = Maximum inductor voltage when the power switch is “on.” Typically max VIN for the Boost and Inverting converters. = 100 for Boost and 125 for Inverting 3582512fb 18 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION Maximum Load Currents: Use one of the following equations to estimate the maximum output load current for the positive and negative output voltages: IOUTP = ⎛ VIN(MIN) ⎞ ⎛ TOFF _ MIN • (VOUTP + 0.5 – VIN(MIN) )⎞ ⎜ ⎟• ⎜IPK – ⎟• 0.8η 2•L ⎝ VOUTP ⎠ ⎝ ⎠ or IOUTN = ⎛ ⎞ ⎛ VIN(MIN) • (|VOUTN | +0.5)⎞ T ⎜ ⎟ • ⎜IPK – OFF _ MIN ⎟ • 0.8η ⎜V ⎟ 2•L ⎠ ⎝ IN(MIN) + |VOUTN |⎠ ⎝ where: VOUT = Regulation voltage VIN(MIN) = Minimum input voltage. = Peak inductor current. See the Peak IPK Current Rating section. Use minimum ILIMIT rating for these calculations. η = Power conversion efficiency (about 88% for Boost or 78% for Inverting) TOFF_MIN = Minimum switch off time. Typically 100ns for Boost and 125ns for Inverting. = Output load current IOUT For example, if VOUTP = 10V, VOUTN = –10V, VIN = 5V, and L = 4.7μH then IOUTP = 117mA and IOUTN = 105mA. Note: The 155mA (Typ) current limit of the output disconnect PMOS (see Electrical Characteristics) may limit maximum IOUTP unless CAPP is shorted to VOUTP. See the Improving Boost Converter Efficiency section. Maximum Slew Rate: Lower inductance causes higher current slew rates which can lead to current limit overshoot. Choose an inductance higher than LMIN to limit the overshoot: LMIN = VIN(MAX) • 0.2μH where VIN(MAX) is the maximum input voltage. Using the previous example VIN = 3V, LMIN = 0.6μH. Capacitor Selection The small size and low ESR of ceramic capacitors makes them suitable for most LT3582 series applications. X5R and X7R types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V or Z5U. A 4.7μF input capacitor and a 2.2μF to 10μF output capacitor are sufficient for most LT3582 series applications. Always use a capacitor with a sufficient voltage rating. Many capacitors rated at 2.2μF to 10μF, particularly 0805 or 0603 case sizes, have greatly reduced capacitance at the desired output voltage. Generally a 1206 capacitor will be adequate. A 0.22μF to 1μF capacitor placed on the CAPP node is recommended to filter the inductor current while the larger 2.2μF to 10μF placed on the VOUTP and VOUTN nodes will give excellent transient response and stability. Avoid placing large value capacitors (generally > 6.8μF) on both CAPP and VOUTP. This configuration can be less stable since it creates two poles, one at the CAPP pin and the other at the VOUTP pin, which can be near each other in frequency. Table 4 shows a list of several capacitor manufacturers. Consult the manufacturers for more detailed information and for their entire selection of related parts. Table 4. Ceramic Capacitor Manufacturers MANUFACTURER PHONE URL Kemet 408-986-0424 www.kemet.com Murata 814-237-1431 www.murata.com Taiyo Yuden 408-573-4150 www.t-yuden.com TDK 847-803-6100 www.tdk.com Diode Selection Schottky diodes, with their low forward voltage drops and fast switching speeds, are recommended for use with the LT3582 series. The Diodes Inc. B0540WS is a very good choice in a small SOD-323 package. This diode is rated to handle an average forward current of 500mA and performs well across a wide temperature range. Schottky diodes with very low forward voltage drops are also available. These diodes may improve efficiency at moderate and cold temperatures, but will likely reduce efficiency at higher temperatures due to excessive reverse leakage currents. 3582512fb 19 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION Output Disconnect Operating Limits Improving Boost Converter Efficiency The LT3582 series has a PMOS output disconnect switch connected between CAPP and VOUTP. During normal operation, the switch is closed and current is internally limited to about 155mA (see Figure 9). Make sure that the output load current doesn’t exceed the PMOS current limit. Exceeding the current limit causes a significant rise in PMOS power consumption which may damage the device. The efficiency of the Boost converter can be improved by shorting the CAPP pin to the VOUTP pin (see Figure 11). The power loss in the PMOS disconnect circuit is then made negligible. In most applications, the associated CAPP pin capacitor can be removed and the larger VOUTP capacitor can adequately filter the output voltage. During shutdown, the PMOS switch is open and CAPP is isolated from VOUTP up to a voltage difference of 5-5.5V. In most cases this allows VOUTP to discharge to ground. However, when the Boost inductor input exceeds 5.5V, the CAPP-VOUTP voltage may exceed 5V allowing some current flow through the PMOS switch. In addition, applying CAPPVOUTP voltages in excess of 5.7V(typical) may activate internal protection circuitry which turns the PMOS “on” (see Figure 10). If the current is not limited, this can lead to a sharp increase in the PMOS power consumption and may damage the device. If this situation cannot be avoided, limit PMOS power consumption to less than 1/3 Watt (about 50mA at 7V) to avoid damaging the device. Refer to the Absolute Maximum Ratings table for maximum limits on CAPP-VOUTP voltages and currents. 180 ICAPP-VOUTP 20μA/DIV Figure 10. PMOS Current vs Voltage During Shutdown 4 3 13 160 SWN SWP SWN VIN CAPP GND LT3582 PMOS CURRENT (mA) 140 CAPP VOUTP 120 2 100 VOUTN VPP SDA 80 SCL 60 8 40 20 3582512 F11 VCAPP-VOUTP 1V/DIV SHDN RAMPP RAMPN 7 6 CA 12 5 11 10 C1 ILOAD 9 14 15 16 1 3582512 F12 0 0 100 200 300 CAPP-VOUTP (mV) 400 500 Figure 11. Improved Efficiency 3582512 F10 Figure 9. PMOS Current vs Voltage During Normal Operation 3582512fb 20 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION Note that the ripple voltage on VOUTP will typically increase in this configuration since the output disconnect PMOS, when not shorted, helps to create an RC filter at the output. Also, if the VOUTP pin is shorted to CAPP, the power-down discharge should not be enabled. VOUTP cannot be discharged to ground during shutdown due to the path from VIN to VOUTP through the external inductor and diode. Finally, due to the path from VIN to VOUTP , current will flow through the integrated feedback resistor whenever voltage is present on VIN. the switching regulator to minimize interplane coupling. Suggested component placement is shown in Figure 12. Make sure to include the ground plane cuts as shown in Figure 12. The switching action of the regulators can cause large current steps in the ground plane. The cuts reduce noise by recombining the current steps into a continuous flow under the chip, thus reducing di/dt related ground noise in the ground plane. CA SCL SDA VPP CVPP (OPT) Inrush Current When the Boost inductor input voltage (usually VIN) is stepped from ground to the operating voltage, a high level of inrush current may flow through the inductor and Schottky diode into the CAPP capacitor. Conditions that increase inrush current include a larger more abrupt voltage step at the inductor input, larger CAPP capacitors and inductors with low inductances and/or low saturation currents. For circuits that use output capacitor values within the recommended range and have input voltages of less than 5V, inrush current remains low, posing no hazard to the devices. In cases where there are large input voltage steps (more than 5V) and/or a large CAPP capacitor is used, inrush current should be measured to ensure safe operation. 16 VOUTN 15 14 13 L1 1 12 COUTN 17 2 L2 GND CIN 11 3 10 4 9 5 VIN 6 7 CCAPP COUTP 8 SHDN VOUTP VIAS TO GROUND PLANE UNDER PIN 17 REQUIRED TO IMPROVE THERMAL PERFORMANCE Thermal Lockout If the die temperature reaches approximately 147°C, the part will go into thermal lockout. In this event, the chip is reset which turns off the power switches and starts to discharge the RAMP capacitors. The part will be re-enabled when the die temperature drops by about 3.5°C. Board Layout Considerations As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. To maximize efficiency, switch rise and fall times are made as short as possible. To prevent electromagnetic interference (EMI) problems, proper layout of the high frequency switching path is essential. The voltage signals of the SWP and SWN pins have sharp rising and falling edges. Minimize the length and area of all traces connected to the SWP/SWN pins and always use a ground plane under GROUND PLANE 3582512 F13 Figure 12. Suggested Component Placement (Not to Scale) 3582512fb 21 LT3582/LT3582-5/LT3582-12 APPLICATIONS INFORMATION D1 L1 6.8μH SWN SHDN SWN VIN INPUT 4.5V TO 5.5V SWP L2 6.8μH GND D2 LT3582 C2 4.7μF VNEG –12V 85mA CAPP VOUTN CAPP SDA I2C INTERFACE OPTIONAL ON LT3582-12 C1 4.7μF C4 1μF SCL CA VPOS 12V 80mA VOUTP VPP RAMPP RAMPN C5 10nF REG0/OTP0 = B0h REG1/OTP1 = D8h REG2/OTP2 = 03h C3 3582512 TA05a C6 10nF D1-D2: DIODES INC. B0540WS-7 L1-L2: COILCRAFT XPL2010-682 C1: 4.7μF, 6.3V, X5R, 0805 C2: 4.7μF, 16V, X5R, 0805 C3: 1s 4.7μF OR 2s 4.7μF OR 10μF 16V, X5R, 0805 C4: 1μF, 16V, X5R, 0603 C5-C6: 10nF, 0603 Figure 13. ±12V Outputs from a Single 5V Input VOUTP Ripple VOUTN Ripple and C2 Selection 80 25 4.7μF 16V 0805 X5R OUTPUT RIPPLE (mV) OUTPUT RIPPLE (mV) 20 15 10 60 10μF 16V 0805 X5R 40 2× 4.7μF 16V 0805 X5R 20 5 0 0 0 20 40 60 LOAD CURRENT (mA) 80 0 20 40 60 LOAD CURRENT (mA) 3582512 TA05b 80 3582512 TA05c Also See Typical Characteristics and Front Page for Additional Data 3582512fb 22 LT3582/LT3582-5/LT3582-12 TYPICAL APPLICATION ±5V Outputs from a Single 2.7V to 3.8V Input D1 L1 6.8μH SWN SHDN SWN VIN INPUT 2.7V TO 3.8V SWP L2 6.8μH GND D2 LT3582 VNEG –5V 100mA (VIN ≥ 2.7V) 125mA (VIN ≥ 3.3V) C2 10μF CAPP VOUTN I2C INTERFACE OPTIONAL ON LT3582-5 CAPP SDA VOUTP SCL VPP CA RAMPP RAMPN C5 22nF REG0/OTP0 = 24h REG1/OTP1 = 4Ch REG2/OTP2 = 03h C3 10μF C6 22nF D1-D2: DIODES INC. B0540WS-7 L1-L2: COILCRAFT LPS4018-682ML C1: 4.7μF, 6.3V, X5R, 0805 C2-C3: 10μF, 6.3V, X5R 0805 C4: 1μF, 6.3V, X5R, 0603 C5-C6: 22nF, 0603 Efficiency and Power Loss, Load from VOUTN to GND 100 VIN = 3.3V VPOS 5V 100mA (VIN ≥ 2.7V) 124mA (VIN ≥ 3.3V) 3582512 TA02a Efficiency and Power Loss, Load from VOUTP to GND 95 C1 4.7μF C4 1μF 95 180 VIN = 3.3V 90 160 85 80 50 65 40 55 30 EFFICIENCY (%) 60 140 100 65 80 55 60 40 20 45 120 75 45 20 10 0.1 1 10 LOAD CURRENT (mA) 0 100 35 1 10 LOAD CURRENT (mA) 0.1 3582512 TA02b 0 100 3582512 TA02c Efficiency and Power Loss, Load from VOUTP to VOUTN 95 300 VIN = 3.3V 85 250 75 200 65 150 55 100 45 50 35 0.1 1 10 LOAD CURRENT (mA) POWER LOSS (mW) EFFICIENCY (%) 35 POWER LOSS (mW) 70 75 POWER LOSS (mW) EFFICIENCY (%) 85 0 100 3582512 TA02d 3582512fb 23 LT3582/LT3582-5/LT3582-12 TYPICAL APPLICATION ±5V Outputs from a Single 2.7V to 3.8V Input (Improved Efficiency) D1 L1 6.8μH SWN SHDN SWN VIN SWP GND C2 10μF C3 10μF C1 4.7μF CAPP VOUTN I2C INTERFACE OPTIONAL ON LT3582-5 L2 6.8μH D2 LT3582 VNEG –5V 100mA (VIN ≥ 2.7V) 125mA (VIN ≥ 3.3V) INPUT 2.7V TO 3.8V CAPP SDA VOUTP SCL VPP CA RAMPP RAMPN C5 22nF REG0/OTP0 = 24h REG1/OTP1 = 4Ch REG2/OTP2 = 03h VPOS 5V 110mA (VIN ≥ 2.7V) 150mA (VIN ≥ 3.3V) 3582512 TA03 C6 22nF D1-D2: DIODES INC. B0540WS-7 L1-L2: COILCRAFT LPS4018-682ML C1: 4.7μF, 6.3V, X5R, 0805 C2-C3: 10μF, 6.3V, X5R, 0805 C4: 1μF, 6.3V, X5R, 0603 C5-C6: 22nF, 0603 Efficiency and Power Loss, Load from VOUTP to GND 95 80 VIN = 3.3V 70 85 50 65 40 30 55 POWER LOSS (mW) EFFICIENCY (%) 60 75 20 45 10 35 0.1 1 10 LOAD CURRENT (mA) 0 100 3582512 TA03a 3582512fb 24 LT3582/LT3582-5/LT3582-12 TYPICAL APPLICATION 12V and –5V Outputs from a Single 2.7V to 5.5V Input D1 L1 6.8μH SWN SHDN SWN VIN INPUT 2.7V TO 5.5V SWP L2 6.8μH GND D2 LT3582 C2 10μF VNEG –5V 100mA CAPP SDA VOUTP SCL VPP CA RAMPP RAMPN C5 22nF REG0/OTP0 = B0h REG1/OTP1 = 4Ch REG2/OTP2 = 0Bh C3 4.7μF 3582512 TA04a D1-D2: DIODES INC. B0540WS-7 L1-L2: COILCRAFT LPS4018-682ML C1: 4.7μF, 6.3V, X5R, 0805 C2: 10μF, 6.3V, X5R, 0805 C3: 4.7μF, 16V, X5R, 0805 C4: 1μF, 16V, X5R, 0603 C5-C6: 22nF, 0603 Efficiency and Power Loss, Load from VOUTN to GND 95 100 VIN = 3.6V VPOS 12V 38mA (VIN = 2.7) 58mA (VIN = 3.6) 95mA (VIN = 5.5) C6 22nF Efficiency and Power Loss, Load from VOUTP to GND 95 C1 4.7μF CAPP VOUTN I2C INTERFACE C4 1μF 180 VIN = 3.6V 90 160 85 80 60 50 65 40 55 30 EFFICIENCY (%) 75 140 100 65 80 55 60 40 20 45 120 75 45 20 10 0 100 35 1 10 LOAD CURRENT (mA) 35 1 10 LOAD CURRENT (mA) 0.1 0 100 3582512 TA04c 3582512 TA04b Efficiency and Power Loss, Load from VOUTP to VOUTN 95 200 VIN = 3.6V 180 85 160 140 75 120 100 65 80 55 60 POWER LOSS (mW) EFFICIENCY (%) 0.1 POWER LOSS (mW) 70 POWER LOSS (mW) EFFICIENCY (%) 85 40 45 20 35 0.1 1 10 LOAD CURRENT (mA) 0 100 3582512 TA04d 3582512fb 25 LT3582/LT3582-5/LT3582-12 PACKAGE DESCRIPTION UD Package 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 p0.05 3.50 p 0.05 1.45 p 0.05 2.10 p 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 p0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 p 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP OR 0.25 s 45o CHAMFER R = 0.115 TYP 0.75 p 0.05 15 PIN 1 TOP MARK (NOTE 6) 16 0.40 p 0.10 1 1.45 p 0.10 (4-SIDES) 2 (UD16) QFN 0904 0.200 REF 0.00 – 0.05 NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.25 p 0.05 0.50 BSC 3582512fb 26 LT3582/LT3582-5/LT3582-12 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION B 11/09 Revised Title and Add text to Description PAGE NUMBER 1 Revised Pin Configuration 2 Added Text to I2C Interface Section 11 Revised Typical Application Drawings 22, 23, 24 3582512fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 27 LT3582/LT3582-5/LT3582-12 TYPICAL APPLICATION Tiny AMOLED Power Supply is 0.8mm (Max) Thin INPUT 2.7V TO 4.2V VIN SWP L2 1.5μH GND D2 LT3582 C2 10μF VNEG –5V 90mA C4 10μF CAPP SDA I2C INTERFACE 250 C1 10μF CAPP VOUTN CA VPOS 4.6V 100mA VOUTP SCL VPP RAMPP RAMPN C5 10nF 300 80 EFFICIENCY (%) SWN 350 VIN = 3.3V 70 200 60 150 50 100 40 C3 10μF 50 30 3582512 TA06a 0.1 C6 10nF POWER LOSS (mW) L1 1.5μH 90 SHDN SWN D1 Efficiency and Power Loss, Load from VOUTP to VOUTN 1 10 LOAD CURRENT (mA) 0 100 3582512 TA06b REG0/OTP0 = 1Ch REG1/OTP1 = 4Ch REG2/OTP2 = 07h D1-D2: PANASONIC M21D3800L LOW VF SCHOTTKY L1-L2: TDK MLP3216S1R5L C1-C4: TAIYO YUDEN JMK212BJ106MK, 6.3V, X5R 0805 C5-C6: 0402 X5R RELATED PARTS PART DESCRIPTION COMMENTS LT1944/LT1944-1(Dual) Dual Output 350mA ISW, Constant Off-Time, High Efficiency Step-Up DC/DC Converter VIN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 20μA, ISD <1μA, MS10 LT1945(Dual) Dual Output, Pos/Neg, 350mA ISW, Constant Off-Time, High Efficiency Step-Up DC/DC Converter VIN: 1.2V to 15V, VOUT(MAX) = ±34V, IQ = 20μA, ISD <1μA, MS10 LT3463/LT3463A Dual Output, Boost/Inverter, 250mA ISW, Constant Off-Time, High Efficiency Step-Up DC/DC Converter with Integrated Schottkys VIN: 2.4V to 15V, VOUT(MAX) = ±40V, IQ = 40μA, ISD <1μA, DFN LT3471 Dual Output, Boost/Inverter, 1.3A ISW, 1.2MHz, High Efficiency Boost-Inverting DC/DC Converter VIN: 2.4V to 16V, VOUT(MAX) = ±40V, IQ = 2.5mA, ISD <1μA, DFN LT3472 Dual Output, Boost/Inverter, 0.35A ISW, 1.2MHz, High Efficiency Boost-Inverting DC/DC Converter VIN: 2.2V to 16V, VOUT(MAX) = ±34V, IQ = 2.8mA, ISD <1μA, DFN LT3477 42V, 3A, 3.5MHz Boost, Buck-Boost, Buck LED Driver VIN: 2.5V to 25V, VOUT(MAX) = 40V, IQ = Analog/PWM, ISD <1μA, QFN, TSSOP-20E LT3494/LT3494A 180/350mA (ISW), Low Noise High Efficiency Step-Up DC/DC Converter VIN: 2.3V to 16V, VOUT(MAX) = 40V, IQ = 65μA, ISD <1μA, 2mm × 3mm DFN LT3495/LT3495B/ LT3495-1/LT3495B-1 650/350mA (ISW), Low Noise High Efficiency Step-Up DC/DC Converter VIN: 2.5V to 16V, VOUT(MAX) = 40V, IQ = 60μA, ISD <1μA, 2mm × 3mm DFN LT1930/LT1930A 1A (ISW), 1.2/2.2MHz, High Efficiency Step-Up DC/DC Converter VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2/5.5mA, ISD <1μA, ThinSOT™ LT1931/LT1931A 1A (ISW), 1.2/2.2MHz, High Efficiency Inverting DC/DC Converter VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2/5.5mA, ISD <1μA, ThinSOT LT3467/LT3467A 1.1A (ISW), 1.3/2.1MHz, High Efficiency Step-Up DC/DC VIN: 2.4V to 16V, VOUT(MAX) = 40V, IQ = 1.2mA, ISD <1μA, ThinSOT Converter with Soft-Start LT1618 1.5A (ISW), 1.4MHz, High Efficiency Step-Up DC/DC Converter LT1946/LT1946A 1.5A (ISW), 1.2/2.7MHz, High Efficiency Step-Up DC/DC VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 3.2mA, ISD <1μA, MS8E Converter VIN: 1.6V to 18V, VOUT(MAX) = 35V, IQ = 1.8mA, ISD <1μA, MS10, DFN ThinSOT is a trademark of Linear Technology Corporation. 3582512fb 28 Linear Technology Corporation LT 0110 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2009