LTC3101 Wide VIN, Multi-Output DC/DC Converter and PowerPath Controller DESCRIPTION FEATURES n n n n n n n n n n n n The LTC®3101 is a complete power management solution for low power portable devices. It provides three high efficiency switching DC/DC converters which seamlessly transition from battery to USB/wall adapter power when available.
LTC3101 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) ENA3 SW3B ENA1 FB2 FB1 ENA2 TOP VIEW 24 23 22 21 20 19 PWM 1 18 HSO SW1 2 17 OUT3 BAT1 3 16 USB2 25 GND USB1 4 15 SW3A SW2 5 14 BAT2 13 RESET PBSTAT CRS 9 10 11 12 MAX 8 LDO 7 FB3 PWRON 6 PWRKEY VBAT1, VBAT2, VUSB1, VUSB2 ......................... –0.3V to 6V VSW1, VSW2, VSW3A, VSW3B DC............................................................ –0.3V to 6V Pulsed (<100ns) ...................................... –1.
LTC3101 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VUSB1 = VUSB2 = VBAT1 = VBAT2 = 3V and VOUT3 = 3.3V, unless otherwise noted. PARAMETER CONDITIONS MIN Minimum Duty Cycle l ENA1 Input Logic Threshold l ENA1 Pull-Down Resistance 0.3 VPWRON = 3V or VPWRKEY = 0V N-Channel Switch Resistance TYP 0.7 Ω Ω VSW1 = VUSB1,2 = VBAT1,2 = 5.5V 0.
LTC3101 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VUSB1 = VUSB2 = VBAT1 = VBAT2 = 3V and VOUT3 = 3.3V, unless otherwise noted. PARAMETER CONDITIONS MIN N-Channel Switch Leakage VSW3A,B = VUSB1,2 = VBAT1,2 = VOUT3 = 5.5V P-Channel Switch Leakage VSW3A,B = 0V, VUSB1,2 = VBAT1,2 = VOUT3 = 5.5V Power Good Threshold VFB3 Falling l –11.5 Power Good Hysteresis TYP MAX UNITS 0.
LTC3101 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise specified) Buck Efficiency 2 AA Cells to 1.5V 90 80 80 PWM Mode 40 100 Burst Mode OPERATION 70 60 PWM Mode 50 40 30 20 L = 4.7μH VBAT = 3.2V VBAT = 1.8V 0 1000 10 1 100 LOAD CURRENT (mA) 3101 G01 100 Burst Mode OPERATION 40 30 L = 4.7μH VBAT = 3.2V VBAT = 1.8V 10 0 80 Burst Mode OPERATION 70 60 PWM Mode 50 40 20 10 10 QUIESCENT CURRENT (μA) VOUT = 1.
LTC3101 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise specified) Current Limit Thresholds vs Temperature 10 240 800 700 SWITCH RDS(ON) (mΩ) BUCK P-CHANNEL CURRENT LIMIT 6 4 2 BUCK-BOOST INDUCTOR CURRENT LIMIT 0 –2 –4 –6 220 PMOS 600 SWITCH RDS(ON) (mΩ) 8 500 NMOS 400 300 200 –10 –50 50 0 TEMPERATURE (°C) 0 –50 100 SWITCH A´ 140 0 50 100 –50 150 100 TEMPERATURE (°C) 250 200 SWITCH RDS(ON) (Ω) SWITCH C 100 50 0 –50 0 0.9 0.30 0.8 0.28 0.26 PMOS SWITCHES 0.
LTC3101 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise specified) Buck-Boost Maximum Load Current, PWM Mode 1200 100 LOAD CURRENT (mA) LOAD CURRENT (mA) VOUT3 = 3.3V 800 600 VOUT3 = 5V 400 200 VOUT3 = 3.3V 80 VOUT3 = 5V 60 40 20 0 1 2 3 4 5 SUPPLY VOLTAGE, VBAT OR VUSB (V) 1 0.10 0.05 0 –0.05 –0.10 –0.15 2 3 4 5 SUPPLY VOLTAGE, VBAT OR VUSB (V) 6 1.0 0.4 0.8 0.2 0.1 0 –0.1 –0.2 –0.3 –0.4 –0.5 1.0 0.4 0.2 0 –0.2 –0.4 –0.6 0.
LTC3101 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise specified) Reverse USB Current vs BAT Voltage PBSTAT Deglitch Duration PBSTAT Deglitch Duration 30 25 25 24 22 20 18 16 14 REVERSE USB CURRENT (μA) 26 DEGLITCH DURATION (ms) DEGLITCH DURATION (ms) 28 24 23 22 21 20 PWM MODE, VUSB = 0V 15 10 5 0 12 10 –50 0 50 100 TEMPERATURE (°C) 20 150 1 2 4 5 3 SUPPLY VOLTAGE, VBAT OR VUSB (V) 3101 G28 REVERSE BAT CURRENT (μA) 140 120 100 80 OUTPUT VOLTAGE 200mV/DIV INDUCTOR
LTC3101 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise specified) Buck-Boost Burst Mode Ripple OUTPUT VOLTAGE 20mV/DIV OUTPUT VOLTAGE 10mV/DIV INDUCTOR CURRENT 200mA/DIV INDUCTOR CURRENT 50mA/DIV VBAT = 3V VOUT = 3.3V L = 4.7μH COUT = 10μF ILOAD = 10mA 20μs/DIV 3101 G34 Buck-Boost Burst to PWM Mode Transient Buck Burst Mode Ripple VOUT3 50mV/DIV VBAT = 5.5V VOUT3 50mV/DIV VBAT = 3V VOUT3 50mV/DIV VBAT = 1.8V VBAT = 3V VOUT = 1.2V L = 4.
LTC3101 PIN FUNCTIONS PWM (Pin 1): Pulse Width Modulation/Burst Mode Selection Input. Forcing this pin high causes all switching converters to operate in low noise fixed frequency PWM mode. Forcing this pin low enables Burst Mode operation for all converters. With PWM held low, the buck-boost converter will operate solely in Burst Mode operation and can only support a minimal load current (typically 50mA).
LTC3101 PIN FUNCTIONS RESET (Pin 13): Active-Low μP Reset and Fault Signal. This pin provides an active-low microprocessor reset signal. During the power-up sequence, the μP reset signal is held low until all converters are in regulation for a duration programmed by the CRS capacitor. In addition, this pin is held low during a fault condition and when the IC is disabled in order to prevent spurious turn-on of the microprocessor. BAT2 (Pin 14): Battery Power Input for the Buck-Boost Converter.
LTC3101 BLOCK DIAGRAM 14 16 BAT2* 15 USB2* 20 SW3A 17 SW3B OUT3 WELL CONTROL MAX CONTROL AND CURRENT LIMIT D HSO 18 A 11 MAX B A´ 10 3 4 C Hot Swap CONTROL ALWAYS-ON LDO CONTROL LDO BAT1* FB3 BUCK-BOOST CONTROL USB1* ENA3 4M WELL CONTROL 7 19 VCC 400k 2 SW1 1.
LTC3101 OPERATION INTRODUCTION The LTC3101 provides a complete power management solution for low power portable devices. It generates a total of six output voltage rails and provides a seamless, automatic transition between two input power sources. The LTC3101 contains three high efficiency synchronous DC/DC converters: a 5-switch buck-boost DC/DC converter and two synchronous 3-switch step-down DC/DC converters. The buck-boost DC/DC converter is typically utilized to provide a 3V or 3.
LTC3101 OPERATION remain enabled. Power-down is usually accomplished by having the microprocessor monitor PBSTAT to detect an additional push of the pushbutton. Once this is detected, the microprocessor disables the LTC3101 by forcing PWRON low (or simply releasing PWRON and allowing it be pulled low by its internal pull-down resistor). In this manner, a single external momentary pushbutton is all that is required to provide sequenced power-up and power-down control.
LTC3101 OPERATION Independent Enables Each of the buck converters and the buck-boost converter have independent enable pins (ENA1, ENA2 and ENA3). These provide an additional degree of flexibility by allowing any unused channels to be independently disabled and skipped in the power-up sequence. For example, if the additional low voltage rail generated by the second buck converter is not required, it can be disabled by simply forcing ENA2 to ground.
LTC3101 OPERATION MAX OUTPUT The MAX output generates a protected output rail that tracks the higher of the two input supplies, BAT2 or USB2. The MAX output is current-limit protected and is guaranteed to support a 200mA load. The MAX output is an always-alive output, meaning it is always enabled independent of the state of the pushbutton interface. This allows the MAX output to power additional LDOs or critical circuitry that must remain powered in standby.
LTC3101 OPERATION Low Dropout Operation Internal Voltage Mode Soft-Start As the input voltage decreases to a value approaching the output regulation voltage, the duty cycle increases to the maximum on-time of the P-channel switch. Further reduction of the supply voltage will force the main switch to remain on for more than one cycle and subharmonic switching will occur to provide a higher effective duty cycle.
LTC3101 OPERATION BUCK-BOOST CONVERTER OPERATION The buck-boost converter is a synchronous 5-switch DC/DC converter with the capability to operate efficiently with input voltages that are above, below or equal to the output regulation voltage. A proprietary switching algorithm provides a smooth transition between operational modes while maintaining high efficiency and low noise performance. Referring to the Block Diagram, the buck-boost converter has two P-channel input power switches, A and A´.
LTC3101 OPERATION transient response of the converter. Increasing the value of R2 generally leads to greater stability at the expense of reduced transient response speed. Increasing the value of R2 can yield substantial transient response improvement in cases where the phase margin has been reduced due to use of a small value output capacitor or a large inductance (particularly with large boost step-up ratios).
LTC3101 OPERATION Power Good Comparator Operation The buck-boost converter contains an internal power good comparator that continuously monitors the voltage of the feedback pin FB3. The output of this comparator is used during power-up for sequencing purposes. In addition, during operation, if the power good comparator indicates a fault condition, CRS and RESET will be driven low. This feature can be used to reset a microprocessor in the application circuit if the buck-boost output loses regulation.
LTC3101 APPLICATIONS INFORMATION The basic LTC3101 application circuit is shown as the Typical Application on the front page of this data sheet. The external component selection is dependent upon the required performance of the IC in each particular application given considerations and tradeoffs such as PCB area, output voltages, output currents, ripple voltages and efficiency.
LTC3101 APPLICATIONS INFORMATION buck converter is going to be utilized at duty cycles over 40%, the inductance value must be at least equal to LMIN as given by the following equation: Table 2. Representative Buck Inductors VALUE (μH) DCR (Ω) MAX DC CURRENT (A) SIZE (mm) W×L×H Coilcraft LPS3015 EPL2014 EPL2010 LPS4018 4.7 4.7 4.7 4.7 0.20 0.23 0.43 0.125 1.2 0.88 0.65 1.9 3.0 × 3.0 × 1.5 2.0 × 2.0 × 1.4 2.0 × 2.0 × 1.0 4.0 × 4.0 × 1.8 Cooper-Bussmann SD3118 SD3112 SD3110 SD10 4.7 4.7 4.7 4.7 0.
LTC3101 APPLICATIONS INFORMATION capacitance of the feedback pin produce a parasitic pole that can reduce the loop phase margin if it becomes too low in frequency. For these reasons, it is recommended that the resistance of R1 in parallel with R2 be kept under 300k. A reasonable compromise between noise immunity and quiescent current is provided by choosing R2 = 221k. The required value for R1 can then be calculated via Equation 1. Table 3.
LTC3101 APPLICATIONS INFORMATION If a substantially larger output capacitor is utilized, the bandwidth of the loop will be reduced. In such cases, the feedforward capacitor can be increased in value in order to lower the zero frequency and improve the transient response. Buck-Boost Output Voltage Programming The buck-boost output voltage is set via an external resistor divider connected to the FB3 pin as shown in Figure 5.
LTC3101 APPLICATIONS INFORMATION provides a small sampling of inductors that are well suited to many LTC3101 buck-boost converter applications. All inductor specifications are listed at an inductance value of 4.7μH for comparison purposes but other values within these inductor families are generally well suited to this application. Within each family (i.e., at a fixed size), the DC resistance generally increases and the maximum current generally decreases with increased inductance. Table 5.
LTC3101 APPLICATIONS INFORMATION to lose 45% of its rated capacitance when operated near its rated voltage. As a result, it is sometimes necessary to use a larger value capacitance or a capacitor with a higher voltage rating than required in order to actually realize the intended capacitance at the full operating voltage. For details, consult the capacitor vendor’s curve of capacitance versus DC bias voltage.
VUSB VBAT VOUT2 INNER COPPER LAYER INNER COPPER LAYER (21) ENA1 (10) LDO (22) FB2 (9) PBSTAT (23) FB1 (8) PWRKEY (24) ENA2 (7) FB3 (13) RESET (14) BAT2 (15) SW3A (16) USB2 (17) OUT3 (18) HSO INNER COPPER LAYER Figure 6.
LTC3101 TYPICAL APPLICATIONS 2 AA Cell/USB/Wall Adapter Power Supply with Six Output Rails and Pushbutton On/Off C4 10μF CELLS USB POWER 4.3V TO 5.5V WALL ADAPTER 4.0V TO 5.5V C5 10μF C3 10μF L3 4.7μH BAT1 BAT2 SW3A USB1 USB2 LTC3101 ON/OFF VOUT1 L2 4.7μH R6 221k PWRKEY 5V/DIV 100 VOUT1 2V/DIV 80 VOUT2 2V/DIV 70 EFFICIENCY (%) 3101 TA02b C10 22pF C1 10μF VOUT2 1.8V 350mA R5 110k R4 221k VOUT1 1.
LTC3101 TYPICAL APPLICATIONS Manual Enable with Simultaneous Start-Up + 2 AA C3 10μF CELLS USB POWER 4.3V TO 5.5V C2 10μF C4 10μF 4.7μH BAT1 BAT2 SW3A USB1 USB2 R1 1M VOUT3 = 3.3V 300mA FOR VIN ≥ 1.8V 800mA FOR VIN ≥ 3V R2 221k SW3B OUT3 FB3 HSO Hot Swap OUTPUT 3.3V 100mA C5 4.7μF MAX PWM PWRON TRACKING OUTPUT 200mA C6 4.7μF LDO DISABLE ENABLE C1 0.22μF ENA1 ENA2 ENA3 LTC3101 4.7μH SW2 R3 221k CRS 1.8V 50mA C7 4.7μF C8 22pF C9 10μF C10 22pF C11 10μF VOUT2 1.
LTC3101 TYPICAL APPLICATIONS Li-Ion/USB-Powered Six Output Power Supply with Pushbutton Control Li-Ion 1.8V TO 4.2V + C3 10μF USB POWER 4.3V TO 5.5V C2 10μF C4 10μF L3 4.7μH BAT1 BAT2 SW3A USB1 USB2 R3 1M R4 221k SW3B OUT3 FB3 HSO CRS TRACKING OUTPUT 200mA C6 4.7μF LDO LTC3101 ON/OFF Hot Swap OUTPUT 3.3V 100mA C5 4.7μF MAX ENA3 ENA2 ENA1 C1 0.22μF VOUT3 = 3.3V 300mA FOR VIN ≥ 1.8V 800mA FOR VIN ≥ 3V L2 4.7μH SW2 PWRKEY R5 221k VOUT2 1.8V 50mA C7 4.
LTC3101 TYPICAL APPLICATIONS Sequenced Start-Up, Buck-Boost Followed by Buck Converters + 2 AA C3 10μF CELLS USB POWER 4.3V TO 5.5V C2 10μF C4 10μF 4.7μH BAT1 BAT2 SW3A USB1 USB2 LTC3101 R5 100k R4 221k C5 0.1μF Hot Swap OUTPUT 3.3V 100mA C6 4.7μF MAX PWM ENA3 CRS ON/OFF R3 1M SW3B OUT3 FB3 ENA2 ENA1 HSO C1 0.033μF VOUT3 = 3.3V 300mA FOR VIN ≥ 1.8V 800mA FOR VIN ≥ 3V TRACKING OUTPUT 200mA C7 4.7μF LDO 4.7μH SW2 PWRKEY R6 221k VOUT1 C9 22pF C10 10μF C11 22pF C12 10μF VOUT2 1.
LTC3101 PACKAGE DESCRIPTION UF Package 24-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1697) 0.70 ±0.05 4.50 ± 0.05 2.45 ± 0.05 3.10 ± 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 4.00 ± 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD R = 0.115 TYP 0.75 ± 0.05 PIN 1 NOTCH R = 0.20 TYP OR 0.35 × 45° CHAMFER 23 24 PIN 1 TOP MARK (NOTE 6) 0.40 ± 0.10 1 2 2.45 ± 0.10 (4-SIDES) (UF24) QFN 0105 0.200 REF 0.00 – 0.05 0.25 ± 0.05 0.50 BSC NOTE: 1.
LTC3101 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION B 4/10 Added Graphs G41 and G42 PAGE NUMBER 8 Text Changed on Pin 25 11 Updated Related Parts 34 3101fb 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.
LTC3101 TYPICAL APPLICATION 2 AA Cell/USB/Wall Adapter Power Supply with Six Output Rails and Pushbutton On/Off + 2 AA C4 10μF CELLS USB POWER 4.3V TO 5.5V WALL ADAPTER 4.0V TO 5.5V C5 10μF C3 10μF L3 4.7μH BAT1 BAT2 SW3A USB1 USB2 LTC3101 VOUT1 LDO μP C9 22pF R6 221k L1 4.7μH R2 50k 1.8V 50mA C6 4.7μF L2 4.7μH FB2 PBSTAT PWRON RESET PWM TRACKING OUTPUT 200mA C7 4.7μF SW2 PWRKEY R1 50k Hot Swap OUTPUT 3.3V 100mA C8 4.