LTC3246 Wide VIN Range Buck-Boost Charge Pump with Watchdog Timer DESCRIPTION FEATURES n n n n n n n n n n n n 2.7V - 38V Operating Range (42V Abs Max) IQ = 20A Operating, 1.5A in Shutdown Multimode Buck-Boost Charge Pump (2:1, 1:1, 1:2) with Automatic Mode Switching 12V to 5V Efficiency = 81% IOUT Up to 500mA VOUT: Fixed 3.3V, 5V or Adjustable (2.5V to 5V) Ultralow EMI Emissions Engineered for Diagnostic Coverage in ISO 26262 Systems Overtemperature, Overvoltage and Short-Circuit Protection Operating Junction Temperature: 150C Max POR/Watchdog Controller w/External Timing Control Thermally Enhanced 16-Lead MSOP Package The LTC(R)3246 is a switched capacitor buck-boost DC/DC converter with integrated watchdog timer. The device produces a regulated output (3.3V, 5V or adjustable) from a 2.7V to 38V input. Switched capacitor fractional conversion is used to maintain regulation over a wide range of input voltage. Internal circuitry automatically selects the conversion ratio to optimize efficiency as input voltage and load conditions vary. No inductors are required. The LTC3246's reset time and watchdog timeout may be set without external components, or adjusted using external capacitors. A windowed watchdog function is used for high reliability applications. The reset input can be used for additional supply monitoring or be configured as a pushbutton reset. Low operating current (20A without load, 1.5A in shutdown) and low external parts count make the LTC3246 ideally suited for low power, space constrained automotive/industrial applications. The device is short-circuit and overtemperature protected and is available in a thermally enhanced 16-lead MSOP package. APPLICATIONS n n n Automotive ECU/CAN Transceiver Supplies Industrial/Telecom Housekeeping Supplies Low Power 12V to 5V Conversion All registered trademarks and trademarks are the property of their respective owners. TYPICAL APPLICATION Regulated 5V Output with Pushbutton Reset Output Voltage vs Input Voltage 2.2F VIN 1F SEL2 SEL1 BIAS 10F C- VOUT OUTS/ADJ LTC3246 RST WDI 5.15 VOUT = 5V IOUT UP TO 500mA 500k 10F 5.10 500k C 5.05 VOUT (V) VIN = 2.7V TO 38V C+ 5.20 4.95 4.90 RT WT 5.00 GND RSTI 3246 TA01a 4.85 RESET 4.80 IOUT = 50mA IOUT = 500mA 0 2 4 6 8 10 12 14 16 VIN (V) 3246 TA01b For more information www.linear.com/LTC3246 3246fa 1 LTC3246 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Notes 1, 2) VIN, SEL1, SEL2, WDI ................................. -0.3V to 42V VOUT, OUTS/ADJ, RSTI, WT, RT, BIAS, RST . -0.3V to 6V IRST ........................................................................10mA VOUT Short Circuit Duration ............................. Indefinite Lead Temperature (Soldering, 10 sec)................... 300C Operating Junction Temperature Range (Notes 3, 4) (E-Grade/I-Grade) .................................. -40 to 125C (H-Grade) ............................................... -40 to 150C (MP-Grade) ............................................ -55 to 150C Storage Temperature Range ......................-65 to 150C ORDER INFORMATION TOP VIEW WT RT RSTI BIAS SEL2 VIN SEL1 BIAS 1 2 3 4 5 6 7 8 17 16 15 14 13 12 11 10 9 OUTS/ADJ GND RST C- VOUT C+ WDI VIN MSE PACKAGE 16-LEAD PLASTIC MSOP TJMAX = 150C, JA = 40C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB http://www.linear.com/product/LTC3246#orderinfo LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3246EMSE#PBF LTC3246EMSE#TRPBF 3246 16-Lead Plastic MSOP -40C to 125C LTC3246IMSE#PBF LTC3246IMSE#TRPBF 3246 16-Lead Plastic MSOP -40C to 125C LTC3246HMSE#PBF LTC3246HMSE#TRPBF 3246 16-Lead Plastic MSOP -40C to 150C LTC3246MPMSE#PBF LTC3246MPMSE#TRPBF 3246 16-Lead Plastic MSOP -55C to 150C Consult ADI Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult ADI Marketing for information on nonstandard 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 specified operating junction temperature range, otherwise specifications are at TA = 25C. VIN = 12V, CFLY = 2.2F, COUT = 10F, unless otherwise noted. SYMBOL PARAMETER CONDITIONS (Note 5) MIN VIN Operating Input Voltage Range VUVLO VIN Undervoltage Lockout Threshold IVIN VIN Quiescent Current Shutdown CP Enabled, Output in Regulation VHIGH SEL1, SEL2 Input Voltage l VLOW SEL1, SEL2 Input Voltage l ILOW SEL1, SEL2 Input Current IHIGH SEL1, SEL2 Input Current l TYP MAX 38 V 2.35 2.7 V 1.5 20 3 30 A A 1.1 1.6 V 2.7 l SEL1 = SEL2 = 0V SEL1 = VIN and/or SEL2 = VIN, RSTI = 5V UNITS 0.4 0.8 VPIN = 0V l V -1 0 1 A VPIN = 38V l 0.5 1 2 A 4.8 5.2 3.17 3.43 Charge Pump Operation VOUTS_5 VOUTS/ADJ Regulation Voltage SEL1 = 0V, SEL2 = VIN 2.7V < VIN < 38V (Notes 5, 6) l VOUTS_3 VOUTS/ADJ Regulation Voltage SEL1 = VIN, SEL2 = VIN 2.7V < VIN < 38V (Notes 5, 6) l VADJ VOUTS/ADJ Regulation Voltage SEL1 = VIN, SEL2 = 0V 2.7V < VIN < 38V (Notes 5, 6) l 2 1.08 1.11 1.14 V V V 3246fa For more information www.linear.com/LTC3246 LTC3246 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25C. VIN = 12V, CFLY = 2.2F, COUT = 10F, unless otherwise noted. SYMBOL PARAMETER IADJ VOUTS/ADJ Input Current SEL1 = SEL2 = VIN IOUT_SCKT IVOUT Short Circuit Foldback Current VOUT = 0V 250 mA ROUT Charge Pump Output Impedance 2:1 Step-Down Mode 1:1 Step-Down Mode, VIN = 5.5V 1:2 Step-Up Mode, VIN = 3V, VOUT 3.3V (Note 6) l 1 1.2 4 % of Final Regulation Voltage at Which VOUT Rising Makes RST Go Low VOUT Falling Makes RST Go Hi-Z l l 106 109 108.5 111.5 % % % of Final Regulation Voltage at Which VOUT Rising Makes RST Go Hi-Z VOUT Falling Makes RST Go Low l l 93 97.5 95 99 % % VOUT_OV_RST VOUT_UV_RST VOUT Overvoltage Reset VOUT Undervoltage Reset CONDITIONS l MIN TYP MAX UNITS -50 0 +50 nA 8 VOUT_PD VOUT Pull-Down in Shut Down SEL1 = SEL2 = 0V 100 k VOUT_RIPPLE VOUT Ripple Voltage COUT = 10F COUT = 22F 50 25 mV mV Reset Timer Control Pin (RT) IRT(UP) RT Pull-Up Current VRT = 0.3V l -2 -3.1 -4.2 A IRT(DOWN) RT Pull-Down Current VRT = 1.3V l 2 3.1 4.2 A IRT(INT) Internal RT Detect Current VRT = VBIAS l 0.4 1 A VRT(INT) RT Internal Timer Threshold VRT Rising l 2.4 2.65 V 1.22 1.27 2.0 Reset Timer Input (RSTI) VRSTI_H RSTI Input High Voltage l VRSTI_L RSTI Input Low Voltage l 1.04 1.2 V IRSTI_H RSTI Input High Current RSTI = 5V l -1 0 1 A IRSTI_L RSTI Input Low Current RSTI = 0V l -1 0 1 A V Reset Timing tRST(INT) Internal Reset Timeout Period VRT = VBIAS tRST(EXT) Adjustable Reset Timeout Period CRT = 2.2nF tRSTIL RSTI Low to RST Asserted 150 200 270 ms l 14 21 28 ms l 5 20 40 s 0.1 0.4 V Reset Output (RST) VOL(RST) Output Voltage Low RST IRST = 2mA l IOH(RST) RST Output Voltage High Leakage VRST = 5V l -1 0 1 A 1.6 2.2 s Watchdog Timing tWDU(INT) Internal Watchdog Upper Boundary VWT = VBIAS l 1.2 37.5 50 68 ms 100 160 220 ms tWDL(INT) Internal Watchdog Lower Boundary VWT = VBIAS l tWDR(EXT) External Watchdog Timeout Period CWT = 2.2nF l tWDU(EXT) External Watchdog Upper Boundary l tWDR(EXT) * (128/129) ms tWDL(EXT) External Watchdog Lower Boundary l tWDR(EXT) * (5/129) ms Watchdog Timer Input (WDI) VIH WDI Input High Voltage l VOL WDI Input Low Voltage l 0.4 1.1 0.8 1.6 V IIH WDI Input High Current VWDI = 38V l -1 0 1 A IIL WDI Input Low Current VWDI = 0V l -1 0 1 A tPW(WDI) Input Pulsewidth l 400 V ns 3246fa For more information www.linear.com/LTC3246 3 LTC3246 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25C. VIN = 12V, CFLY = 2.2F, COUT = 10F, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS -3.1 -4.2 A Watchdog Timer Control Pin (WT) IWT(UP) WT Pull-Up Current VWT = 0.3V l -2 IWT(DOWN) WT Pull-Down Current VWT = 1.3V l 2 IWT(INT) Internal WT Detect Current VWT = VBIAS l VWT(INT) WT Internal Timer Threshold VWT Rising l 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: All voltages are referenced to GND unless otherwise specified. Note 3: The LTC3246E is guaranteed to meet performance specifications from 0C to 85C operating junction temperature. Specifications over the -40C to 125C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC3246I is guaranteed over the -40C to 125C operating junction temperature range. The LTC3246H is guaranteed over the -40C to 150C operating junction temperature range. The LTC3246MP is guaranteed and tested over the -55C to 150C operating junction temperature range. High junction temperatures degrade operating lifetimes; operating lifetime is derated for junction temperatures greater than 125C. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. 10 9 1000 A 1 A 2.2 2.65 V TA = 25C, unless otherwise noted. Input Operating Current vs Input Voltage TA = 125C TA = 25C 4.2 The junction temperature (TJ, in C) is calculated from the ambient temperature (TA, in C) and power dissipation (PD, in watts) according to the formula: TJ = TA + (PD * JA), where JA (in C/W) is the package thermal impedance. Note 4: This IC has overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperatures will exceed 150C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 5: The maximum operating junction temperature of 150C must be followed. Certain combinations of input voltage, output current and ambient temperature will cause the junction temperature to exceed 150C and must be avoided. See Thermal Management section for information on calculating maximum operating conditions. Note 6: The LTC3246 will attempt to regulate the output voltage under all load conditions, but like any regulator, the output will drop out if inadequate supply voltage exists for the load. See VOUT Regulation section for calculating available load current at low input operating voltages. Also see "Boost Output Impedance at Dropout vs Temperature" for typical impedance values at output voltages less than 3.3V. TYPICAL PERFORMANCE CHARACTERISTICS Input Shutdown Current vs Input Voltage 2 3.1 0.4 Input Operating Current vs Input Voltage NO LOAD 60 125C 25C -55C 8 TA = 125C TA = 25C TA = -55C 50 7 40 5 4 IIN (A) IIN (A) IIN (A) 6 100 30 20 3 2 10 1 0 0 4 8 12 16 20 24 28 32 36 40 VIN (V) 0 5 10 15 20 25 30 35 40 VIN (V) 3246 G01 4 10 0 NO LOAD 4 6 8 10 12 14 16 VIN (V) 3246 G02 3246 G03 3246fa For more information www.linear.com/LTC3246 LTC3246 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, unless otherwise noted. 3.3V Fixed Output Voltage vs Input Voltage 3.3V Fixed Output Voltage vs Input Voltage 3.45 3.45 3.40 3.40 3.3V Efficiency and Power Loss vs Input Voltage 100 90 EFFICIENCY (%) VOUT (V) VOUT (V) 3.25 3.30 3.25 IOUT = 0mA IOUT = 50mA IOUT = 500mA 3.20 0 2 4 6 8 10 12 14 3.15 16 0 4 8 0.5 40 0.4 0 5.15 5.15 90 5.05 VOUT (V) 5.05 5.00 4.95 4.90 EFFICIENCY (%) 100 5.00 IOUT = 0mA IOUT = 50mA IOUT = 500mA 4.85 6 8 4.95 10 12 14 4.80 16 0 4 8 10 100 70 7 70 60 6 50 5 40 4 30 3 LOSS EFFICIENCY (%) 80 0.8 0.7 0.5 0.4 30 0.3 LOSS 20 0.2 10 0 0.1 0 2 4 6 8 10 12 14 16 0.0 3246 G09 8 EFFICIENCY 7 4 30 0 0 0 16 9 5 10 14 10 IOUT = 500mA 40 20 12 0.6 EFFICIENCY 50 1 10 0.9 70 6 2 8 1.0 80 60 10 6 0.0 3 LOSS POWER LOSS (W) 90 8 POWER LOSS (W) 9 4 16 3.3V Efficiency and Power Loss vs Input Voltage EFFICIENCY 20 14 VIN (V) 80 2 12 3246 G08 IOUT = 500mA 0 10 IOUT = 50mA VIN (V) 5V Efficiency and Power Loss vs Input Voltage 90 8 40 12 16 20 24 28 32 36 40 3246 G07 100 6 50 IOUT = 0mA IOUT = 50mA IOUT = 500mA 4.85 VIN (V) EFFICIENCY (%) 4 4 60 4.90 2 2 5V Efficiency and Power Loss vs Input Voltage 5.20 0 0 3246 G06 5.20 4.80 0.1 VIN (V) 5V Fixed Output Voltage vs Input Voltage 5.10 0.2 10 3246 G05 5.10 0.3 LOSS POWER LOSS (W) VOUT (V) 50 VIN (V) 3246 G04 5V Fixed Output Voltage vs Input Voltage 0.7 0.6 20 12 16 20 24 28 32 36 40 VIN (V) 0.8 60 30 IOUT = 0mA IOUT = 50mA IOUT = 500mA 3.20 0.9 EFFICIENCY 70 3.35 3.30 3.15 80 POWER LOSS (W) 3.35 1.0 IOUT = 50mA 2 1 0 2 4 VIN (V) 6 8 10 12 14 16 0 VIN (V) 3246 G10 3246 G11 3246fa For more information www.linear.com/LTC3246 5 LTC3246 TYPICAL PERFORMANCE CHARACTERISTICS Boost Output Impedance at Dropout vs Temperature 7.0 1.18 6.5 1.16 6.0 1.14 5.5 1.12 5.0 1.10 1.08 Internal Reset Timeout Period vs Temperature 300 IOUT = 500mA 275 250 TIME (ms) 1.20 RO () VADJ (V) ADJ Regulation Voltage vs Temperature 4.5 4.0 1.06 3.5 1.04 3.0 1.02 2.5 1.00 -60 -40 -20 0 TA = 25C, unless otherwise noted. 2.0 -60 -45 -30 -15 0 20 40 60 80 100 120 140 TEMPERATURE (C) 200 175 150 VOUT = 2.5V VOUT = 3.0V VOUT = 3.3V VOUT = 5.0V 125 100 -60 -40 -20 0 15 30 45 60 75 90 TEMPERATURE (C) 3246 G13 Internal Watchdog Timeout Period vs Temperature 3246 G14 RT/WT Timer Control Current vs Temperature 2.0 3.5 1.9 3.4 VIN = 12V VIN = 2.7V 3.3 1.8 3.2 |IRT/WT| (A) 1.7 1.6 1.5 3.1 3.0 2.9 2.8 1.4 2.7 1.3 2.6 1.2 -60 -40 -20 0 2.5 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) 20 40 60 80 100 120 140 TEMPERATURE (C) 3246 G15 10000 20 40 60 80 100 120 140 TEMPERATURE (C) 3246 G12 TIME (s) 225 Reset Timeout Period vs CRT Capacitance 100000 1000 10000 100 1000 3246 G16 BIAS Output Voltage vs Input Voltage Watchdog Timeout Period vs CWT Capacitance 6.0 5.5 10 VBIAS (V) TIME (ms) TIME (ms) 5.0 100 4.5 4.0 1 0.1 0.001 10 0.01 0.1 1 10 100 1000 CRT (nF) 0.01 0.1 1 10 100 1000 CWT (nF) 3246 G17 6 1 0.001 3.5 3.0 VOUTSD VOUTEN 0 5 10 15 20 25 30 35 40 VIN (V) 3246 G18 3246 G19 3246fa For more information www.linear.com/LTC3246 LTC3246 TYPICAL PERFORMANCE CHARACTERISTICS Output Transient Response TA = 25C, unless otherwise noted. Output Voltage Ripple 2:1 MODE 50mV/DIV VOUT 50mV/DIV 1:1 MODE 50mV/DIV 1:2 MODE 50mV/DIV 440mA IOUT 25mA 5s/DIV VIN = 14V VOUT = 5V COUT = 10F 1s/DIV IOUT = 400mA COUT = 10F 3246 G20 3246 G21 TIMING DIAGRAMS Charge Pump Output Reset Timing RSTI tRSTIL tRST RST 3246 TD01 Watchdog Timing WDI RST t < tWDL tRST tWDL < t < tWDU tWDR tRST 3246 TD02 3246fa For more information www.linear.com/LTC3246 7 LTC3246 PIN FUNCTIONS WT (Pin 1): Watchdog Timer Control Pin. Attach an external capacitor (CWT) to GND to set a watchdog upper boundary timeout time (See "Watchdog Timeout Period vs WT Capacitance" graph on page 6). Tie WT to BIAS to generate a timeout of about 1.6s. Tie WT and WDI to GND to disable the watchdog timer. RT (Pin 2): Reset Timeout Control Pin. Attach an external capacitor (CRT) to GND to set a reset timeout time (See "Reset Timeout Period vs RT Capacitance" graph on page 6). Tie RT to BIAS to generate a reset timeout of about 200ms. RSTI (Pin 3): Reset Logic Comparator Pin. The RSTI input is compared to a reference threshold (1.2V typical). If RSTI is below the reference voltage, the part will enter the reset state and the RST pin will be low. Once RSTI exceeds the reference voltage and VOUT in regulation, the reset timer is started. RST pin will be low until the reset period times out. RSTI is a high impedance pin and must be driven to a valid level. Do not float. BIAS (Pin 4, 8): Internal BIAS Voltage. The bias pin is for internal operation only and should not be loaded or driven externally. Bypass BIAS with a 10F or greater ceramic capacitor. SEL2 (Pin 5): Logic Input Pin. See Table 1 for SEL1/SEL2 operating logic. SEL2 enables and disables the charge pump along with the SEL1 pin. The SEL2 pin has a 1A (typical) pull down current to ground and can tolerate 38V inputs allowing it to be pin-strapped to VIN. VIN (Pin 6, 9): Power Input Pin. Input voltage for both charge pump and IC control circuitry. The VIN pin operates from 2.7V to 38V. All VIN pins should be connected together at pins and bypassed with a 1F or greater ceramic capacitor. SEL1 (Pin 7): Logic Input Pin. See Table 1 for SEL1/SEL2 operating logic. SEL1 enables and disables the charge pump along with the SEL2 pin. The SEL1 pin has a 1A (typical) pull down current to ground and can tolerate 38V inputs allowing it to be pin-strapped to VIN. 8 Table 1. VOUT Operating Modes SEL2 SEL1 MODE LOW LOW Shutdown LOW HIGH Adjustable VOUT HIGH LOW Fixed 5V HIGH HIGH Fixed 3.3V WDI (Pin 10): Watchdog Logic Input Pin. If the watchdog timer is not disabled then WDI must be driven such that a falling edge occurs within a time less than the watchdog upper boundary time, or RST will be asserted low. The WDI period must also be greater than the watchdog lower boundary time, and only falling edges are considered. Tie WT and WDI to GND to disable the watchdog timer. WDI is a high impedance pin and must be driven to a valid level. Do not float. C+ (Pin 11): Connect to positive flying capacitor terminal only. Do not load or drive externally. VOUT (Pin 12): Charge Pump Output Voltage. The charge pump output is enabled if either SEL1 or SEL2 are logic high. C- (Pin 13): Connect to negative flying capacitor terminal only. Do not load or drive externally. RST (Pin 14): Reset Open Drain Logic Output. The RST pin is low impedance during the reset period, and goes high impedance during the watchdog period. RST is intended to be pulled up to low voltage supply (such as VOUT) with an external resistor. GND (Pin 15, Exposed Pad): Ground. The exposed package pad is ground and must be soldered to the PC board ground plane for proper functionality and for rated thermal performance. OUTS/ADJ (Pin 16): VOUT Sense/Adjust Input Pin. This pin acts as VOUT sense (OUTS) for 5V or 3.3V fixed outputs and adjust (ADJ) for adjustable output through external feedback. The ADJ pin servos to 1.1V when the device is enabled in adjustable mode. (OUTS/ADJ are selected by SEL1 and SEL2 pins; See Table 1). Connect OUTS/ADJ to VOUT or external divider as appropriate. 3246fa For more information www.linear.com/LTC3246 LTC3246 SIMPLIFIED BLOCK DIAGRAM 2.2F 11 13 C+ VIN 2.7V TO 38V 6 VIN ILIM C- 17 CHARGE PUMP GND 1F 9 4 VIN 5V LDO BIAS VOUT 10F 8 15 BIAS MODE 2 VIN VOUT CLK 10F OUT MODE COMP OSC EN 12 + ADJ OUTS/ ADJ VOUT 3.5V/5V/ADJ 500mA 16 1.1V 3.3V MUX - 5V PGOOD +9%/-5% SEL1 UP TO 38V 7 SEL2 UP TO 38V 5 SEL2 1.2V RSTI 0V TO 5V 3 WDI UP TO 38V 10 SD SEL1 RSTI WDI - RST + 14 RESET TIMER WATCHDOG TIMER WT 1 RT 2 CWT 3246 BD CRT 3246fa For more information www.linear.com/LTC3246 9 LTC3246 APPLICATIONS INFORMATION General Operation The LTC3246 uses switched capacitor based DC/DC conversion to provide the efficiency advantages associated with inductor based circuits as well as the cost and simplicity advantages of a linear regulator. The LTC3246 uses an internal switch network and fractional conversion ratios to achieve high efficiency and regulation over widely varying VIN and output load conditions. Internal control circuitry selects the appropriate conversion ratio based on VIN and load conditions. The device has three possible conversion modes: 2:1 step-down mode, 1:1 step-down mode and 1:2 step-up mode. Only one external flying capacitor is needed to operate in all three modes. 2:1 mode is chosen when VIN is greater than two times the desired VOUT. 1:1 mode is chosen when VIN falls between two times VOUT and VOUT. 1:2 mode is chosen when VIN falls below the desired VOUT. The internal mode control logic maintains output regulation over all load conditions. Regulation is achieved by sensing the output voltage and enabling charge transfer when the output falls below regulation. When the charge pump is enabled, it controls the current into the flying capacitor to limit the output ripple beyond that of conventional switched capacitor charge pumps. The part has two SEL pins that select the output regulation (fixed 5V, fixed 3.3V or adjustable) as well as shutdown. The charge pump operates at a nominal frequency of about 450kHz, though actual output ripple frequency will vary with output load, operating mode and output capacitance. The LTC3246 is designed for applications requiring high system reliability. The part includes output supply monitoring and watchdog timing circuitry as well as overvoltage, short-circuit and overtemperature protection. VOUT Regulation and Mode Selection Regulation is achieved by sensing the output voltage and enabling charge transfer when the output falls below the programmed regulation voltage. The amount of charge transferred per cycle is controlled over the full input range to minimize output ripple. The regulation voltage (fixed 5V, fixed 3.3V or adjustable) is selected through the SEL1 and SEL2 pins per Table 1 in the Pin Function section. 10 The optimal conversion ratio is chosen based on VIN, VOUT and output conditions. Two internal comparators are used to select the default conversion ratio. The conversion ratio switch point is optimized to provide peak efficiency over all supply and load conditions while maintaining regulation. Each comparator also has built-in hysteresis to reduce the tendency of oscillating between modes when a transition point is reached. The LTC3246 will attempt to regulate its output over the full operating range (2.7V to 38V), but like any regulator the output will drop out of regulation if inadequate supply voltage exists to the operating load. As the input voltage drops, the LTC3246 will eventually end up in the 1:2 step up mode. As the input voltage drops further, the output will eventually drop out of regulation. At this point, the 1:2 step-up charge pump impedance can be calculated as: R OUT = 2 * VIN - VOUT IOUT This equation can be rewritten to determine the output current at which the output will drop out for a given input voltage as: IOUT = 2 * VIN - VOUT R OUT IOUT 500mA For a typical 1:2 step-up charge pump impedance of 4 with 5V output voltage and 3V input voltage, the output current at dropout will be about: IOUT = 2 * 3 - 4.8 4 mA = 300mA Thus, typically the part should be able to output 300mA without dropping out. To be conservative, the max 1:2 step-up charge pump impedance of 8 should be used which gives a more conservative output current of 150mA. Any supply impedance in series with the LTC3246 must be doubled and added to the 1:2 step-up charge pump impedance. It is also important to have the specified COUT and CFLY capacitance to achieve the specified output impedance. Observing dropout will allow the user to calculate the output impedance for their specific application. 3246fa For more information www.linear.com/LTC3246 LTC3246 APPLICATIONS INFORMATION Short-Circuit/Thermal Protection The LTC3246 has built-in short-circuit current limiting on both the VOUT and BIAS outputs to protect the part in the event of a short. During short-circuit conditions, the device will automatically limit the output current from both outputs. The LTC3246 has thermal protection that will shut down the device if the junction temperature exceeds the overtemperature threshold (typically 175C). Thermal shutdown is included to protect the IC in cases of excessively high ambient temperatures, or in cases of excessive power dissipation inside the IC. The charge transfer will reactivate once the junction temperature drops back to approximately 165C. When the thermal protection is active, the junction temperature is beyond the specified operating range. The thermal and short-circuit protection are intended for momentary overload conditions outside normal operation. Continuous operation above the specified maximum operating conditions may impair device reliability. Programming the Output Voltage (OUTS/ADJ Pin) The LTC3246 output voltage programming is very flexible offering a fixed 3.3V output, fixed 5V output as well as adjustable output that is programmed through an external resistor divider. The desired output regulation method is selected through the SEL pins. For a fixed output simply short OUTS (OUTS/ADJ pin) to VOUT as shown in Figure 1. Fixed 3.3V operation is enabled by driving both SEL1 and SEL2 pins high, while fixed 5V operating is selected by driving SEL2 high with SEL1 low. Driving both SEL1 and SEL2 low shuts down the device causing VOUT to be pulled low by an internal impedance of about 80k. VOUT FIXED 3.3V OR FIXED 5.0V VOUT LTC3246 OUTS/ADJ COUT Adjustable output programming is accomplished by connecting ADJ (OUTS/ADJ pin) to a resistor divider between VOUT and GND as shown in Figure 2. Adjustable operation is enabled by driving SEL1 high and SEL2 low. Driving both SEL1 and SEL2 low shuts down the device, causing VOUT to be pulled low by an internal impedance of about 80k. VOUT VOUT LTC3246 RA COUT OUTS/ADJ 1.1V 1 RA RB RB GND 3246 F02 Figure 2. Adjustable Output Operation Using adjustable operation, the output (VOUT) can be programmed to regulate from 2.5V to 5V. The limited programming range provides the required VOUT operating voltage without overstressing the VOUT pin. The desired adjustable output voltage is programmed by solving the following equation for RA and RB: V = OUT - 1 RB 1.11V RA Select a value for RB in the range of 1k to 1M and solve for RA. Note that the resistor divider current adds to the total no load operating current. Thus, a larger value for RB will result in lower operating current. 2:1 Step-Down Charge Pump Operation When the input supply is greater than about two times the output voltage, the LTC3246 will operate in 2:1 stepdown mode. Charge transfer happens in two phases. On the first phase, the flying capacitor (CFLY) is connected between VIN and VOUT. On this phase, CFLY is charged up and current is delivered to VOUT. On the second phase, the flying capacitor (CFLY) is connected between VOUT and GND. The charge stored on CFLY during the first phase is transferred to VOUT on the second phase. When in 2:1 step-down mode, the input current will be approximately GND 3246 F01 Figure 1. Fixed Output Operation 3246fa For more information www.linear.com/LTC3246 11 LTC3246 APPLICATIONS INFORMATION half of the total output current. The efficiency ( ) and chip power dissipation (PD) in 2:1 are approximately: POUT V *I 2V = OUT OUT = OUT 1 PIN VIN VIN * IOUT 2 PD = VIN 2 - VOUT IOUT VOUT Ripple and Capacitor Selection The type and value of capacitors used with the LTC3246 determine output ripple and charge pump strength. The value of COUT directly controls the amount of output ripple for a given load current. Output ripple decreases with output capacitance until about 20F, at which point output peak to peak ripple remains more or less constant. See Figure 3 for graph of output ripple vs output capacitance. 200 1:1 Step-Down Charge Pump Operation *I V V = OUT OUT = OUT PIN VIN * IOUT VIN POUT 150 125 100 75 50 25 0 0 5 10 15 20 25 30 COUT CAPACITANCE (F) 35 40 3246 TA01b Figure 3. Typical VOUT Ripple Voltage vs COUT Capacitance PD = VIN - VOUT IOUT 1:2 Step-Up Charge Pump Operation When the input supply is less than the output voltage, the LTC3246 will operate in 1:2 step-up mode. Charge transfer happens in two phases. On the first phase, the flying capacitor (CFLY) is connected between VIN and GND. On this phase, CFLY is charged up. On the second phase, the flying capacitor (CFLY) is connected between VIN and VOUT and the charge stored on CFLY during the first phase is transferred to VOUT. When in 1:2 step-up mode, the input current will be approximately twice the total output current. Thus, efficiency ( ) and chip power dissipation (PD) in 1:2 are approximately: V *I V = OUT OUT = OUT PIN VIN * 2IOUT 2VIN VOUT RIPPLE (mVP-P) When the input supply is less than about two times the output voltage, but more than the programmed output voltage, the LTC3246 will operate in 1:1 step-down mode. This method of regulation is very similar to a linear regulator. Charge is delivered directly from VIN to VOUT through most of the oscillator period. The charge transfer is briefly interrupted at the end of the period. When in 1:1 step-down mode, the input current will be approximately equal to the total output current. Thus, efficiency ( ) and chip power dissipation (PD) in 1:1 are approximately: POUT BOOST, 500mA BOOST, 50mA BUCK, 500mA BUCK, 50mA LDO, 500mA LDO, 50mA 175 To reduce output noise and ripple, it is suggested that a low ESR (equivalent series resistance < 0.1) ceramic capacitor (10F or greater) be used for COUT. For optimal performance, it is best to increase COUT for low VOUT as the ripple becomes a larger percentage of the regulation voltage degrading performance. Tantalum and aluminum capacitors can be used in parallel with a ceramic capacitor to increase the total capacitance but are not recommended to be used alone because of their high ESR. VOUT Overvoltage Protection An internal comparator monitors the voltage at VOUT and will prevent charge transfer in the event that VOUT exceeds the overvoltage threshold (5.9V typ.). Overvoltage protection is added as a safety feature to prevent damage to the part in the event of a fault such as VOUTS/ADJ pin shorted to ground or not connected to VOUT. Charge transfer will start once the output falls to about 5.75V. PD = 2VIN - VOUT IOUT 12 3246fa For more information www.linear.com/LTC3246 LTC3246 APPLICATIONS INFORMATION VIN Capacitor Selection The finite charge transfer architecture used by the LTC3246 makes input noise filtering much less demanding than the sharp current spikes of conventional regulated charge pumps. Depending on the mode of operation, the input current of the LTC3246 can step from about 1A to 0A on a cycle-by-cycle basis. Low ESR will reduce the voltage steps caused by changing input current, while the absolute capacitor value will determine the level of ripple. The total amount and type of capacitance necessary for input bypassing is very dependent on the applied source impedance as well as existing bypassing already on the VIN node. For optimal input noise and ripple reduction, it is recommended that a low ESR ceramic capacitor be used for CIN bypassing. An electrolytic or tantalum capacitor may be used in parallel with the ceramic capacitor on CIN to increase the total capacitance, but, due to the higher ESR, it is not recommended that an electrolytic or tantalum capacitor be used alone for input bypassing. The LTC3246 will operate with capacitors less than 1F, but, depending on the source impedance, input noise can feed through to the output causing degraded performance. For best performance 1F or greater total capacitance is suggested for CIN. material will retain most of its capacitance from -40C to 85C, whereas a Z5U or Y5V style capacitor will lose considerable capacitance over that range (60% to 80% loss typical). Z5U and Y5V capacitors may also have a very strong voltage coefficient, causing them to lose an additional 60% or more of their capacitance when the rated voltage is applied. Therefore, when comparing different capacitors, it is often more appropriate to compare the amount of achievable capacitance for a given case size rather than discussing the specified capacitance value. For example, over rated voltage and temperature conditions, a 4.7F, 10V, Y5V ceramic capacitor in an 0805 case may not provide any more capacitance than a 1F, 10V, X5R or X7R available in the same 0805 case. In fact, over bias and temperature range, the 1F, 10V, X5R or X7R will provide more capacitance than the 4.7F, 10V, Y5V. The capacitor manufacturer's data sheet should be consulted to determine what value of capacitor is needed to ensure minimum capacitance values are met over operating temperature and bias voltage. Below is a list of ceramic capacitor manufacturers and how to contact them: MANUFACTURER WEBSITE AVX www.avxcorp.com Kemet www.kemet.com Flying Capacitor Selection Murata www.murata Ceramic capacitors should always be used for the flying capacitor. The flying capacitor controls the strength of the charge pump. In order to achieve the rated output current, it is necessary for the flying capacitor to have at least 1F of capacitance over operating temperature with a bias voltage equal to the programmed VOUT (see Ceramic Capacitor Selection Guidelines). If only 100mA or less of output current is required for the application, the flying capacitor minimum can be reduced to 0.2F. The voltage rating of the ceramic capacitor should be VOUT + 1V or greater. Taiyo Yuden www.t-yuden.com TDK www.tdk.com Wurth Elektronik www.we-online.com Ceramic Capacitor Selection Guidelines Capacitors of different materials lose their capacitance with higher temperature and voltage at different rates. For example, a ceramic capacitor made of X5R or X7R BIAS Pin and Capacitor Selection The BIAS pin of the LTC3246 is a 5V output that is generated by an internal Low Drop-Out (LDO) regulator supplied by VIN. The BIAS voltage is used as a supply for the internal low voltage circuitry. A capacitor on the BIAS pin is necessary to stabilize the LDO output and minimize ripple during transient conditions. A low ESR ceramic capacitor with a minimum capacitance of 2F over temperature with 5V bias should be used. Since the BIAS voltage comes from an LDO, the BIAS voltage will drop with VIN as VIN goes below 5V. This is normal and expected operation. The BIAS pin voltage is for internal circuitry only and should not be loaded externally. 3246fa For more information www.linear.com/LTC3246 13 LTC3246 APPLICATIONS INFORMATION The LTC3246 pulls the RST open-drain output low whenever RSTI is below threshold (typically 1.2V) or VOUT is greater than the overvoltage threshold or less than the undervoltage threshold. RST remains asserted low for a reset timeout period (tRST) once RSTI goes above the threshold and VOUT is in regulation (within the overvoltage and undervoltage thresholds). RST de-asserts by going high impedance at the end of the reset timeout period. The reset timeout can be configured to use an internal timer without external components or an adjustable timer programmed by connecting an external capacitor from the RT pin to GND. Glitch filtering ensures reliable reset operation without false triggering. During initial power up, the RST output asserts low while VIN is below the VIN undervoltage lockout threshold. The state of VOUT and RSTI have no effect on RST while VIN is below the undervoltage lockout threshold. The reset timeout period cannot start until VIN exceeds the undervoltage lockout threshold. VOUT Undervoltage/Overvoltage Reset A built-in VOUT supply monitor ensures the VOUT is in regulation before RST is allowed to go high impedance. The monitor detects both overvoltage and undervoltage faults. If VOUT is greater than the overvoltage threshold or less than the undervoltage threshold, the part registers a fault and pulls RST low. The fault condition is removed when VOUT is within the overvoltage and undervoltage thresholds. Load transients within the operating range of the part will not registering as a fault by design. Selecting the Reset Timing Capacitor The reset timeout period can be set to a fixed internal timer or programmed with a capacitor in order to accommodate a variety of applications. Connecting a capacitor, CRT, between the RT pin and GND sets the reset timeout period, tRST. Figure 4 shows the desired reset timeout period as a function of the value of the timer capacitor. Leaving RT 14 open without external capacitor generates a reset timeout of approximately 0.5ms. Shorting RT to BIAS generates a reset timeout of approximately 0.2s. 10000 1000 TIME (ms) Reset Generation (RSTI input, RST output) 100 10 1 0.1 0.001 0.01 0.1 1 10 100 1000 CRT (nF) 3246 F04 Figure 4. Reset Timeout Period vs CRT Capacitance RST Output Characteristics RST is an open-drain pin and, thus, requires an external pull-up resistor to a logic supply. RST may be pulled up to any valid logic level (such as VOUT) providing the voltage limits of the pin are observed (See Absolute Maximum Ratings section). Watchdog Timer (WDI input, RST output) The LTC3246 includes a windowed watchdog function that can continuously monitor the application's logic or microprocessor and issue automatic resets to aid recovery from unintended lockups or crashes. With the RSTI input held above threshold, the application must periodically toggle the logic state of the watchdog input (WDI pin) in order to clear the watchdog timer. Specifically, successive falling edges on the WDI pin must be spaced by more than the watchdog lower boundary but less than the watchdog upper boundary. As long as this condition holds, RST remains high impedance. If a falling edge arrives before the watchdog lower boundary, or if the watchdog timer reaches the upper boundary without seeing a falling edge on WDI, the watchdog timer immediately enters its reset state and asserts RST 3246fa For more information www.linear.com/LTC3246 LTC3246 APPLICATIONS INFORMATION low for the reset timeout period. Once the reset timeout completes, RST is released to go high and the watchdog timer starts again. During power-up, the watchdog timer remains cleared while RST is asserted low. As soon as the reset timer times out, RST goes high and the watchdog timer is started. 128 129 The external watchdog lower boundary (tWDL(EXT)) occurs five clock cycles into the watchdog timeout period (tWDR(EXT)). Thus the external watchdog lower boundary can be calculated from the external watchdog timeout period as: 5 129 The internal watchdog lower boundary can be calculated from the internal watchdog timeout period by the following: t WDL(INT) = t WDR(INT) TIME (ms) The watchdog upper boundary (tWDU) and lower boundary (tWDL) are not observable outside the part; only the watchdog timeout period (tWDR) of the part is observable via the RST pin. The watchdog upper boundary (tWDU) occurs one watchdog clock cycle before the watchdog timeout period (tWDR). The internal watchdog timeout period consists of 8193 clock cycles, so the internal watchdog upper boundary time is essentially the same as the internal watchdog timeout period. Conversely, the external watchdog timeout period consists of only 129 clock cycles, so the external watchdog upper boundary should be more accurately calculated as: t WDL EXT = t WDR(EXT) * 100000 10000 Setting the Watchdog Timeout Period t WDU(EXT) = t WDR(EXT) * Figure 5 shows the approximate external watchdog timeout period as a function of the watchdog capacitor. Shorting WT to BIAS sets an upper and lower watchdog timeout period of about 50ms and 1.6s respectively. 1000 100 10 1 0.001 0.01 0.1 1 10 100 1000 CWT (nF) 3246 F05 Figure 5. External Watchdog Timeout Period vs CWT Capacitance Layout Considerations Due to the high switching frequency and transient currents produced by the LTC3246, careful board layout is necessary for optimal performance. A true ground plane and short connections to all capacitors will optimize performance, reduce noise and ensure proper regulation over all conditions. When using the LTC3246 with an external resistor divider it is important to minimize any stray capacitance to the ADJ (OUTS/ADJ pin) node. Stray capacitance from ADJ to C+ or C- can degrade performance significantly and should be minimized and/or shielded if necessary. Minimize stray capacitance from WT and RT to C+ and C- when using external timing capacitors to minimize timing variation. Thermal Management/Thermal Shutdown 32 The watchdog upper boundary is adjustable and can be optimized for software execution. The watchdog upper boundary is adjusted by connecting a capacitor, CWT, between the WT and GND pins. The on-chip power dissipation in the LTC3246 will cause the junction to ambient temperature to rise at rate of typically 40C/W in still air with a good thermal connection to the PC board. Connecting the die pad (Pin 17) with multiple vias to a large gro und plane under the device can reduce the thermal resistance of the package and PC board con3246fa For more information www.linear.com/LTC3246 15 LTC3246 APPLICATIONS INFORMATION siderably. Poor board layout and failure to connect the die pad (Pin 17) to a large ground plane can result in thermal junction to ambient impedance well in excess of 40C/W. It is also possible to get thermal rates less than 40C/W with good airflow over the part and PC board. Thus, the ambient temperature under this condition cannot exceed 102C if the junction temperature is to remain below 150C, and, if the ambient temperature exceeds about 127C, the device will cycle in and out of the thermal shutdown. Because of the wide input operating range, it is possible to exceed the specified operating junction temperature and even reach thermal shutdown (175C typ). Figure 6 and Figure 7 show the available output current vs ambient temperature to ensure the 150C operating junction temperature is not exceeded. Every application will have a slightly different thermal rise than the specified 40C/W, especially applications with good airflow. Calculating the actual thermal rate for a specific application circuit is too complex to be presented here, but the thermal rate can be measured in application. This is done by first taking the final application circuit and enabling the LTC3246 under a known power dissipation (PD) and raising the ambient temperature slowly until the LTC3246 shuts down. Note this temperature as T1. Now, remove the load from the part and raise the ambient temperature slowly until the LTC3246 shuts down again. Note this temperature as T2. The thermal rate can be calculated as: The figures assume worst-case operating conditions and a thermal impedance of 40C/W. It is always safe to operate under the line shown on the graph. Operation above the line is conditional and is the responsibility of the user to calculate worst-case operating conditions (temperature and power) to make sure the part does not exceed the 150C operating junction temperature for extended periods of time. The 2:1 Step-Down Charge Pump Operation, 1:1 StepDown Charge Pump Operation, and 1:2 Step-Up Charge Pump Operation sections provide equations for calculating power dissipation (PD) in each mode. For example, if it is determined that the maximum power dissipation (PD) is 1.2W under normal operation, then the junction to ambient temperature rise will be: TJA = 1.2W * 40C/W = 48C JA = PD/(T2 - T1) Another method for determining maximum safe operating temperature in application is to configure the LTC3246 to operate under the worst case operating power dissipation. Then slowly raise the ambient temperature until the LTC3246 shuts down. At this point the LTC3246 junction temperature will be about 175C, so simply subtract 25C from the shutdown temperature and this is the safe operating temperature for the application. 0.5 0.5 0.3 SAFE OPERATION 0.2 0.1 0.0 25 50 100 75 125 AMBIENT TEMPERATURE (C) 0.3 SAFE OPERATION 0.2 0.1 2.7V < VIN < 22V JA = 40C/W 0 150 0.0 3246 F06 Figure 6. 5V Output Operation vs Ambient Temperature 16 CONDITIONAL OPERATION 0.4 CONDITIONAL OPERATION IOUT (A) IOUT (A) 0.4 2.7V < VIN < 15V JA = 40C/W 0 25 50 100 75 125 AMBIENT TEMPERATURE (C) 150 3246 F07 Figure 7. 3.3V Output Operation vs Ambient Temperature 3246fa For more information www.linear.com/LTC3246 LTC3246 TYPICAL APPLICATIONS Regulated 2.5V Output with Externally Programmed Watchdog Timing 2.2F VIN = 2.7V TO 38V VIN 1F C- VOUT = 2.5V IOUT UP TO 500mA VOUT SEL1 SEL2 BIAS 10F C+ 500k LTC3246 RSTI RT RST 47F C WDI 1270k OUTS/ADJ GND 10nF WT 3246 TA02 1000k 22nF 3246fa For more information www.linear.com/LTC3246 17 LTC3246 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LTC3246#packaging for the most recent package drawings. MSE Package 16-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1667 Rev F) BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 0.102 (.112 .004) 5.10 (.201) MIN 2.845 0.102 (.112 .004) 0.889 0.127 (.035 .005) 8 1 1.651 0.102 (.065 .004) 1.651 0.102 3.20 - 3.45 (.065 .004) (.126 - .136) 0.305 0.038 (.0120 .0015) TYP 16 0.50 (.0197) BSC 4.039 0.102 (.159 .004) (NOTE 3) RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 0.35 REF 0.12 REF DETAIL "B" CORNER TAIL IS PART OF DETAIL "B" THE LEADFRAME FEATURE. FOR REFERENCE ONLY 9 NO MEASUREMENT PURPOSE 0.280 0.076 (.011 .003) REF 16151413121110 9 DETAIL "A" 0 - 6 TYP 3.00 0.102 (.118 .004) (NOTE 4) 4.90 0.152 (.193 .006) GAUGE PLANE 0.53 0.152 (.021 .006) DETAIL "A" 1.10 (.043) MAX 0.18 (.007) SEATING PLANE 1234567 8 0.17 - 0.27 (.007 - .011) TYP 0.50 NOTE: (.0197) 1. DIMENSIONS IN MILLIMETER/(INCH) BSC 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE. 18 0.86 (.034) REF 0.1016 0.0508 (.004 .002) MSOP (MSE16) 0213 REV F 3246fa For more information www.linear.com/LTC3246 LTC3246 REVISION HISTORY REV DATE DESCRIPTION A 12/17 Changed ROUT VIN condition PAGE NUMBER 3 Changed VRSTI_L lower limit 3 Changed IOUT equation resultant to 300mA and text to 150mA 10 Changed circuit pin names 17 3246fa Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. For more information www.linear.com/LTC3246 19 LTC3246 TYPICAL APPLICATION Reduced Ripple 3.3V Output with Watchdog Timing Disabled 2.2F VIN = 2.7V TO 38V VIN C+ SEL2 1F C- 10F VOUT OUTS/ADJ SEL1 BIAS VOUT = 3.3V IOUT UP TO 500mA 500k RST RST LTC3246 22F RSTI RT WT WDI GND 3246 TA03 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3204-3.3/ LTC3204B-3.3/ LTC3204-5/ LTC3204B-5 Low Noise, Regulated Charge Pumps in (2mm x 2mm) DFN Package VIN: 1.8V to 4.5V (LTC3204B-3.3), 2.7V to 5.5V (LTC3204B-5), IQ = 48A, B Version without Burst Mode Operation, 6-Lead (2mm x 2mm) DFN Package LTC3440 600mA (IOUT) 2MHz Synchronous Buck-Boost DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 2.5V, IQ = 25A, ISD 1A, 10-Lead MS Package LTC3441 High Current Micropower 1MHz Synchronous Buck-Boost DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 2.5V, IQ = 25A, ISD 1A, DFN Package LTC3443 High Current Micropower 600kHz Synchronous Buck-Boost DC/DC Converter 96% Efficiency, VIN: 2.4V to 5.5V, VOUT(MIN) = 2.4V, IQ = 28A, ISD < 1A, DFN Package LTC3240-3.3/ LTC3240-2.5 3.3V/2.5V Step-Up/Step-Down Charge Pump DC/DC Converter VIN: 1.8V to 5.5V, VOUT(MAX) = 3.3V/2.5V, IQ = 65A, ISD < 1A, 2mm x 2mm DFN Package LTC3260 Low Noise Dual Supply Inverting Charge Pump VIN Range: 4.5V to 32V, IQ = 100A, 100mA Charge Pump, 50mA Positive LDO, 50mA Negative LDO LTC3261 High Voltage Low IQ Inverting Charge Pump VIN Range: 4.5V to 32V, IQ = 60A, 100mA Charge Pump LTC3245 High Voltage, Low Noise 250mA Buck-Boost Charge Pump VIN Range: 2.7V to 38V, VOUT Range: 2.5V to 5V, IQ = 18A, ISD = 4A, 3mm x 4mm DFN and 12-Pin MSE Packages LTC3255 Wide VIN Range Fault Protected 50mA Step-Down Charge Pump VIN Range: 4V to 48V, VOUT Range: 2.4V to 15V, IQ = 20A, 10-Pin 3mm x 3mm DFN and MSE Packages LTC3256 Wide VIN Range Dual Output 350mA Step-Down Charge Pump with WDT VIN Range: 5.5V to 38V, VOUT Range: 5V/3.3V, IQ = 18A, 16-Pin MSE Package 20 3246fa LT 1217 REV A * PRINTED IN USA www.linear.com/LTC3246 For more information www.linear.com/LTC3246 ANALOG DEVICES, INC. 2016