LTC3566

FEATURES POWER MANAGER ■ High Efficiency Switching PowerPathTM Controller with Bat-TrackTM Adaptive Output Control ■ Programmable USB or Wall Input Current Limit (100mA/500mA/1A) ■ Full Featured Li-Ion/Polymer Battery Charger ■ “Instant-On” Operation with Discharged Battery ■ 1.5A Maximum Charge Current ■ Internal 180mΩ Ideal Diode Plus External Ideal Diode Controller Powers Load in Battery Mode ■ Low No-Load I when Powered from BAT ( VUVLO, Battery Charger Off, IOUT = 0μA VBUS = 0V, IOUT = 0μA (Ideal Diode Mode) VBAT < VTRIKL VPROG VPROG_TRIKL VC/10 hPROG ITRKL VTRIKL ΔVTRKL VRECHRG tTERM tBADBAT hC/10 VCHRG ICHRG PROG Pin Servo Voltage PROG Pin Servo Voltage in Trickle Charge C/10 Threshold Voltage at PROG Ratio of IBAT to PROG Pin Current Trickle Charge Current Trickle Charge Threshold Voltage Trickle Charge Hysteresis Voltage Recharge Battery Threshold Voltage Safety Timer Termination Bad Battery Termination Time End of Charge Indication Current Ratio CHRG Pin Output Low Voltage CHRG Pin Leakage Current Threshold Voltage Relative to VFLOAT Timer Starts When BAT = VFLOAT BAT < VTRKL (Note 5) ICHRG = 5mA VCHRG = 5V –75 3.3 0.42 0.088 BAT < VTRKL BAT Rising 2.7 0.100 100 1022 100 2.85 135 –100 4 0.5 0.1 65 –125 5 0.63 0.112 100 1 3.0 V mV mV Hour Hour mA/mA mV μA 3566fa 3 LTC3566 ELECTRICAL CHARACTERISTICS SYMBOL RON_CHG TLIM NTC VCOLD VHOT VDIS INTC Ideal Diode VFWD RDROPOUT IMAX_DIODE VLDO3V3 RCL_LDO3V3 ROL_LDO3V VIL VIH IPD1 IPD1_CHRGEN VIN1 VOUTUVLO Forward Voltage Internal Diode On-Resistance, Dropout Internal Diode Current Limit Regulated Output Voltage Closed-Loop Output Resistance Dropout Output Resistance Logic Low Input Voltage Logic High Input Voltage ILIM0, ILIM1, EN1, MODE Pull-Down Currents CHRGEN Pull-Down Current Input Supply Voltage VOUT UVLO -VOUT Falling VOUT UVLO - VOUT Rising Oscillator Frequency Input Current VIN1 Connected to VOUT Through Low Impedance. Switching Regulator Disabled in UVLO PWM Mode PWM Mode, IOUT1 = 0μA Burst Mode® Operation, IOUT1 = 0μA Shutdown ● The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, DVCC = 3.3V, RCLPROG = 3.01k, RPROG = 1k, VIN1 = VOUT1 = 3.8V unless otherwise noted. PARAMETER Battery Charger Power FET On Resistance (Between VOUT and BAT) Junction Temperature in Constant Temperature Mode Cold Temperature Fault Threshold Voltage Hot Temperature Fault Threshold Voltage NTC Disable Threshold Voltage NTC Leakage Current Rising Threshold Hysteresis Falling Threshold Hysteresis Falling Threshold Hysteresis VNTC = VBUS = 5V VBUS = 0V, IOUT = 10mA IOUT = 10mA VBUS = 0V 1.6 0mA < ILDO3V3 < 25mA 3.1 3.3 4 23 0.4 1.2 1.6 1.6 2.7 2.5 2.6 2.8 2.25 220 13 0 10 5.5 2.9 2.7 400 20 1 3.5 75.0 33.4 0.7 –50 2 15 0.18 CONDITIONS MIN TYP 0.18 110 MAX UNITS Ω °C 76.5 1.5 34.9 1.5 1.7 50 78.0 36.4 2.7 50 %VBUS %VBUS %VBUS %VBUS %VBUS mV nA mV mV Ω A V Ω Ω V V μA μA V V V MHz μA μA μA Always On 3.3V Supply Logic (ILIM0, ILIM1, EN1, CHRGEN, MODE) Buck-Boost Regulator fOSC IVIN1 1.8 Burst Mode is a registered trademark of Linear Technology Corporation. 3566fa 4 LTC3566 ELECTRICAL CHARACTERISTICS SYMBOL VOUT1(LOW) VOUT1(HIGH) ILIMF1 IPEAK1(BURST) IZERO1(BURST) IMAX1(BURST) VFB1 IFB1 RDS(ON)P RDS(ON)N ILEAK(P) ILEAK(N) RVOUT1 DBUCK(MAX) DBOOST(MAX) tSS1 PARAMETER Minimum Regulated Output Voltage Maximum Regulated Output Voltage Forward Current Limit (Switch A) PWM Mode ● ● ● The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, VBAT = 3.8V, DVCC = 3.3V, RCLPROG = 3.01k, RPROG = 1k, VIN1 = VOUT1 = 3.8V unless otherwise noted. CONDITIONS For Burst Mode Operation or Synchronous PWM Operation 5.50 2 200 –30 50 ● MIN TYP 2.65 5.60 2.5 275 0 MAX 2.75 UNITS V V 3 350 30 A mA mA mA Forward Burst Current Limit (Switch Burst Mode Operation A) Reverse Burst Current Limit (Switch D) Burst Mode Operation Maximum Deliverable Output Current 2.7V ≤ VIN1 ≤ 5.5V, 2.75V ≤ VOUT ≤ 5.5V in Burst Mode Operation (Note 6) Feedback Servo Voltage FB1 Input Current PMOS RDS(ON) NMOS RDS(ON) PMOS Switch Leakage NMOS Switch Leakage VOUT1 Pull-Down in Shutdown Maximum Buck Duty Cycle Maximum Boost Duty Cycle Soft-Start Time PWM Mode PWM Mode ● 0.780 –50 0.800 0.22 0.17 0.820 50 V nA Ω Ω VFB1 = 0.8V Switches A, D Switches B, C Switches A, D Switches B, C –1 –1 10 100 75 0.5 1 1 μA μA kΩ % % ms 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: The LTC3566E is guaranteed to meet performance specifications from 0°C to 85°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: The LTC3566 includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperatures will exceed 125°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 4: Total input current is the sum of quiescent current, IVBUSQ, and measured current given by: VCLPROG/RCLPROG • (hCLPROG + 1) Note 5: hC/10 is expressed as a fraction of measured full charge current with indicated PROG resistor. Note 6: Guaranteed by design. 3566fa 5 LTC3566 TYPICAL PERFORMANCE CHARACTERISTICS Ideal Diode V-I Characteristics 1.0 INTERNAL IDEAL DIODE WITH SUPPLEMENTAL EXTERNAL VISHAY Si2333 PMOS RESISTANCE (Ω) 0.25 TA = 25°C unless otherwise noted. Output Voltage vs Output Current (Battery Charger Disabled) 4.50 BAT = 4V VBUS = 5V 5x MODE Ideal Diode Resistance vs Battery Voltage 0.8 CURRENT (A) 0.20 INTERNAL IDEAL DIODE 0.15 OUTPUT VOLTAGE (V) 4.25 0.6 INTERNAL IDEAL DIODE ONLY 0.4 4.00 BAT = 3.4V 3.75 0.10 INTERNAL IDEAL DIODE WITH SUPPLEMENTAL EXTERNAL VISHAY Si2333 PMOS 0.2 VBUS = 0V VBUS = 5V 0 0 0.04 0.12 0.16 0.08 FORWARD VOLTAGE (V) 0.20 3566 G01 0.05 3.50 0 2.7 3.0 3.6 3.9 3.3 BATTERY VOLTAGE (V) 4.2 3566 G02 3.25 0 200 600 800 400 OUTPUT CURRENT (mA) 1000 3566 G03 USB Limited Battery Charge Current vs Battery Voltage 700 600 CHARGE CURRENT (mA) CHARGE CURRENT (mA) 500 400 300 200 100 VBUS = 5V RPROG = 1k RCLPROG = 3.01k 150 125 100 75 50 25 0 USB Limited Battery Charge Current vs Battery Voltage 25 Battery Drain Current vs Battery Voltage IVOUT = 0μA VBUS = 0V 20 VBUS = 5V RPROG = 1k RCLPROG = 3.01k BATTERY CURRENT (μA) 15 10 VBUS = 5V (SUSPEND MODE) 5 1x USB SETTING, BATTERY CHARGER SET FOR 1A 2.7 3.0 3.3 3.6 3.9 BATTERY VOLTAGE (V) 4.2 3566 G05 5x USB SETTING, BATTERY CHARGER SET FOR 1A 0 3.0 3.3 3.6 2.7 3.9 BATTERY VOLTAGE (V) 4.2 3566 G04 0 2.7 3.0 3.6 3.9 3.3 BATTERY VOLTAGE (V) 4.2 3566 G06 PowerPath Switching Regulator Efficiency vs Output Current 100 90 EFFICIENCY (%) 80 70 60 50 40 0.01 BAT = 3.8V 1x MODE 100 5x, 10x MODE 90 EFFICIENCY (%) Battery Charging Efficiency vs Battery Voltage with No External Load (PBAT/PBUS) RCLPROG = 3.01k RPROG = 1k IVOUT = 0mA 50 5x CHARGING EFFICIENCY 1x CHARGING EFFICIENCY 80 VBUS Quiescent Current vs VBUS Voltage (Suspend) BAT = 3.8V IVOUT = 0mA QUIESCENT CURRENT (μA) 40 30 20 70 10 0.1 OUTPUT CURRENT (A) 1 3566 G07 60 2.7 3.0 3.6 3.9 3.3 BATTERY VOLTAGE (V) 4.2 3566 G08 0 0 1 3 2 VBUS VOLTAGE (V) 4 5 3566 G09 3566fa 6 LTC3566 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Load Current in Suspend 5.0 0.5 TA = 25°C unless otherwise noted. 3.3V LDO Output Voltage vs Load Current, VBUS = 0V 3.4 BAT = 3.9V 4.2V , BAT = 3.4V BAT = 3.5V BAT = 3.6V VBUS Current vs Load Current in Suspend VBUS = 5V BAT = 3.3V RCLPROG = 3.01k OUTPUT VOLTAGE (V) 4.5 OUTPUT VOLTAGE (V) VBUS CURRENT (mA) 0.4 3.2 4.0 0.3 3.0 3.5 0.2 2.8 3.0 VBUS = 5V BAT = 3.3V RCLPROG = 3k 0 0.1 0.3 0.4 0.2 LOAD CURRENT (mA) 0.5 3566 G10 0.1 2.5 0 2.6 0 0.1 0.3 0.4 0.2 LOAD CURRENT (mA) 0.5 3566 G11 BAT = 3V BAT = 3.1V BAT = 3.2V BAT = 3.3V 0 5 15 20 10 LOAD CURRENT (mA) 25 3566 G12 Battery Charge Current vs Temperature 600 500 CHARGE CURRENT (mA) 400 THERMAL REGULATION 300 200 100 RPROG = 2k 10x MODE 0 –40 –20 0 4.21 Battery Charger Float Voltage vs Temperature 3.68 Low-Battery (Instant-On) Output Voltage vs Temperature BAT = 2.7V IVOUT = 100mA 5x MODE OUTPUT VOLTAGE (V) 3.66 4.20 FLOAT VOLTAGE (V) 4.19 3.64 4.18 3.62 20 40 60 80 TEMPERATURE (°C) 100 120 3566 G13 4.17 –40 –15 35 10 TEMPERATURE (°C) 60 85 3566 G14 3.60 –40 –15 35 10 TEMPERATURE (°C) 60 85 3566 G15 Oscillator Frequency vs Temperature 2.6 15 VBUS Quiescent Current vs Temperature VBUS = 5V IVOUT = 0μA QUIESCENT CURRENT (μA) 5x MODE 70 VBUS Quiescent Current in Suspend vs Temperature IVOUT = 0μA 2.4 FREQUENCY (MHz) VBUS = 5V 2.2 BAT = 3V VBUS = 0V BAT = 2.7V VBUS = 0V 1.8 –40 –15 35 10 TEMPERATURE (°C) QUIESCENT CURRENT (mA) BAT = 3.6V VBUS = 0V 12 60 9 50 1x MODE 6 2.0 40 60 85 3566 G16 3 –40 –15 35 10 TEMPERATURE (°C) 60 85 3566 G17 30 –40 –15 35 10 TEMPERATURE (°C) 60 85 3566 G18 3566fa 7 LTC3566 TYPICAL PERFORMANCE CHARACTERISTICS CHRG Pin Current vs Voltage (Pull-Down State) 100 VBUS = 5V BAT = 3.8V BATTERY CURRENT (μA) ILDO3V3 5mA/DIV 0mA VLDO3V3 20mV/DIV AC COUPLED 3566 G2 TA = 25°C unless otherwise noted. Battery Drain Current vs Temperature 50 BAT = 3.8V VBUS = 0V BUCK REGULATORS OFF 3.3V LDO Step Response (5mA to 15mA) CHRG PIN CURRENT (mA) 80 40 60 30 40 20 20 BAT = 3.8V 20μs/DIV 10 0 0 1 3 4 2 CHRG PIN VOLTAGE (V) 5 3566 G19 0 –40 –15 35 10 TEMPERATURE (°C) 60 85 3566 G21 RDS(ON) for Buck-Boost Regulator Power Switches vs Temperature 0.30 PMOS VIN1 = 3V PMOS VIN1 = 3.6V 0.25 PMOS VIN1 = 4.5V PMOS RDS(ON) (Ω) 0.20 0.15 0.10 0.05 0 –55 –35 –15 NMOS VIN1 = 3V NMOS VIN1 = 3.6V NMOS VIN1 = 4.5V 0.40 0.35 NMOS RDS(ON) (Ω) 0.30 0.25 0.20 0.15 0.10 5 25 45 65 85 105 125 TEMPERATURE (°C) 3566 G22 Buck-Boost Regulator Current Limit vs Temperature 2600 2550 VIN1 = 3.6V 2500 ILIMF (mA) VIN1 = 4.5V 2450 2400 2350 2300 –55 –35 –15 IQ (μA) 12.5 12.0 11.5 13.0 VIN1 = 3V 14.0 13.5 Buck-Boost Regulator Burst Mode Operation Quiescent Current VOUT1 = 3.3V VIN1 = 4.5V VIN1 = 3V VIN1 = 3.6V 5 25 45 65 85 105 125 TEMPERATURE (°C) 3566 G23 11.0 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 3566 G24 Buck-Boost Regulator PWM Mode Efficiency 100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.1 1 VOUT1 = 3.3V TA = 27°C TYPE 3 COMPENSATION 10 ILOAD (mA) 100 1000 3566 G25 Buck-Boost Regulator PWM Efficiency vs VIN1 100 90 100 Buck-Boost Regulator vs ILOAD Burst Mode OPERATION 90 CURVES 80 EFFICIENCY (%) 70 60 50 40 30 20 10 VIN1 = 3V VIN1 = 3.6V VIN1 = 4.5V PWM MODE CURVES VIN1 = 3V VIN1 = 3.6V VIN1 = 4.5V EFFICIENCY (%) Burst Mode OPERATION CURVES VIN1 = 3V VIN1 = 3.6V VIN1 = 4.5V 80 PWM MODE CURVES VIN1 = 3V VIN1 = 3.6V VIN1 = 4.5V 70 60 50 40 30 20 VOUT1 = 3.3V 10 TA = 27°C TYPE 3 COMPENSATION 0 3.1 3.9 2.7 3.5 VIN1 (V) ILOAD = 50mA ILOAD = 200mA ILOAD = 1000mA 4.3 4.7 3566 G26 0 0.1 VOUT1 = 5V TA = 27°C TYPE 3 COMPENSATION 1 10 ILOAD (mA) 100 1000 3566 G27 3566fa 8 LTC3566 TYPICAL PERFORMANCE CHARACTERISTICS Buck-Boost Regulator Load Regulation 3.333 3.322 3.311 VOUT1 (V) 3.300 3.289 3.278 VOUT1 = 3.3V TA = 27°C TYPE 3 COMPENSATION 3.267 1 10 ILOAD (mA) 3566 G28 TA = 25°C unless otherwise noted. Buck-Boost Regulator Load Step, 0mA to 300mA Reduction in Current Deliverability at Low VIN1 300 250 200 150 100 50 0 VOUT1 = 3.3V TA = 27°C TYPE 3 COMPENSATION 2.7 3.1 3.5 3.9 VIN1 (V) 4.3 4.7 3566 G29 REDUCTION BELOW 1A (mA) VIN1 = 3V VIN1 = 3.6V VIN1 = 4.5V STEADY STATE ILOAD START-UP WITH A RESISTIVE LOAD START-UP WITH A CURRENT SOURCE LOAD CH1 VOUT1 AC 100mV/DIV CH2 ILOAD DC 200mA/DIV VIN1 = 4.2V VOUT1 = 3.3V L = 2.2μH COUT = 47μF 100μs/DIV 3566 G30 100 1A PIN FUNCTIONS LDO3V3 (Pin 1): 3.3V LDO Output Pin. This pin provides a regulated, always-on, 3.3V supply voltage. LDO3V3 gets its power from VOUT. It may be used for light loads such as a watchdog microprocessor or real time clock. A 1μF capacitor is required from LDO3V3 to ground. If the LDO3V3 output is not used it should be disabled by connecting it to VOUT. CLPROG (Pin 2): USB Current Limit Program and Monitor Pin. A resistor from CLPROG to ground determines the upper limit of the current drawn from the VBUS pin. A fraction of the VBUS current is sent to the CLPROG pin when the synchronous switch of the PowerPath switching regulator is on. The switching regulator delivers power until the CLPROG pin reaches 1.188V. Several VBUS current limit settings are available via user input which will typically correspond to the 500mA and the 100mA USB specifications. A multilayer ceramic averaging capacitor or R-C network is required at CLPROG for filtering. NTC (Pin 3): Input to the Thermistor Monitoring Circuits. The NTC pin connects to a battery’s thermistor to determine if the battery is too hot or too cold to charge. If the battery’s temperature is out of range, charging is paused until it re-enters the valid range. A low drift bias resistor is required from VBUS to NTC and a thermistor is required from NTC to ground. If the NTC function is not desired, the NTC pin should be grounded. FB1 (Pin 4): Feedback Input for the (Buck-Boost) Switching Regulator. When the regulator’s control loop is complete, this pin servos to a fixed voltage of 0.8V. VC1 (Pin 5): Output of the Error Amplifier and Voltage Compensation Node for the (Buck-Boost) Switching Regulator. External Type I or Type III compensation (to FB1) connects to this pin. See Applications Information section for selecting buck-boost loop compensation components. GND (Pins 6, 12): Power GND pins for the buck-boost. SWAB1 (Pin 7): Switch Node for the (Buck-Boost) Switching Regulator. Connected to internal power switches A and B. External inductor connects between this node and SWCD1. MODE (Pin 8): Logic Input. Mode enables Burst Mode functionality for the buck-boost switching regulator when pin is set high. Has a 1.6μA internal pull-down current source. VIN1 (Pin 9): Power Input for the (Buck-Boost) Switching Regulator. This pin will generally be connected to VOUT (Pin 20). A 1μF(min) MLCC capacitor is recommended on this pin. VOUT1 (Pin 10): Regulated Output Voltage for the (BuckBoost) Switching Regulator. 3566fa 9 LTC3566 PIN FUNCTIONS SWCD1 (Pin 11): Switch Node for the (Buck-Boost) Switching Regulator. Connected to internal power switches C and D. External inductor connects between this node and SWAB1. ILIM0 (Pin 13): Logic Input. Control pin for ILIM0 bit of the current limit of the PowerPath switching regulator. See Table 2. Active high. Has a 1.6μA internal pull-down current source. ILIM1 (Pin 14): Logic Input. Control pin for ILIM1 bit of the current limit of the PowerPath switching regulator. See Table 2. Active high. Has a 1.6μA internal pull-down current source. PROG (Pin 15): Charge Current Program and Charge Current Monitor Pin. Connecting a resistor from PROG to ground programs the charge current. If sufficient input power is available in constant-current mode, this pin servos to 1V. The voltage on this pin always represents the actual charge current. CHRG (Pin 16): Open-Drain Charge Status Output. The CHRG pin indicates the status of the battery charger. Four possible states are represented by CHRG: charging, not charging, unresponsive battery and battery temperature out of range. CHRG is modulated at 35kHz and switches between a low and high duty cycle for easy recognition by either humans or microprocessors. See Table 1. CHRG requires a pull-up resistor and/or LED to provide indication. GND (Pin 17): GND pin for USB Power Manager. GATE (Pin 18): Analog Output. This pin controls the gate of an optional external P-channel MOSFET transistor used to supplement the ideal diode between VOUT and BAT. The external ideal diode operates in parallel with the internal ideal diode. The source of the P-channel MOSFET should be connected to VOUT and the drain should be connected to BAT. If the external ideal diode FET is not used, GATE should be left floating. BAT (Pin 19): Single-Cell Li-Ion Battery Pin. Depending on available VBUS power, a Li-Ion battery on BAT will either deliver power to VOUT through the ideal diode or be charged from VOUT via the battery charger. VOUT (Pin 20): Output Voltage of the Switching PowerPath Controller and Input Voltage of the Battery Charger. The majority of the portable product should be powered from VOUT. The LTC3566 will partition the available power between the external load on VOUT and the internal battery charger. Priority is given to the external load and any extra power is used to charge the battery. An ideal diode from BAT to VOUT ensures that VOUT is powered even if the load exceeds the allotted power from VBUS or if the VBUS power source is removed. VOUT should be bypassed with a low impedance ceramic capacitor. VBUS (Pin 21): Primary Input Power Pin. This pin delivers power to VOUT via the SW pin by drawing controlled current from a DC source such as a USB port or wall adapter. SW (Pin 22): Power Transmission Pin for the USB PowerPath. The SW pin delivers power from VBUS to VOUT via the step-down switching regulator. A 3.3μH inductor should be connected from SW to VOUT. CHRGEN (Pin 23): Logic Input. This logic input pin independently enables the battery charger. Active low. Has a 1.6μA internal pull-down current source. EN1 (Pin 24): Logic Input. This logic input pin independently enables the buck-boost switching regulator. Active high. Has a 1.6μA internal pull-down current source. Exposed Pad (Pin 25): Ground. Buck-boost logic and USB Power Manager ground connections. The Exposed Pad should be connected to a continuous ground plane on the printed circuit board directly under the LTC3566. 3566fa 10 LTC3566 BLOCK DIAGRAM 21 VBUS 2.25MHz PowerPath BUCK REGULATOR 3.3V LDO SW 22 LDO3V3 1 VOUT SUSPEND LDO 500μA/2.5mA 2 3 16 20 NTC CHRG CHARGE STATUS 1.2V CHRGEN 3.6V +– 0.3V ENABLE SWAB1 MODE ILIM DECODE LOGIC CHRGEN EN1 ILIM0 ILIM1 MODE GND 6, 12, 17, 25 3566 BD 23 24 13 14 8 1A, 2.25MHz BUCK-BOOST REGULATOR + – + + + BATTERY TEMPERATURE MONITOR – – CLPROG + IDEAL GATE 18 – CC/CV CHARGER 15mV BAT 19 PROG 15 VIN1 9 7 VOUT1 10 SWCD1 11 FB1 4 VC1 5 3566fa 11 LTC3566 OPERATION Introduction The LTC3566 is a highly integrated power management IC which includes a high efficiency switch mode PowerPath controller, a battery charger, an ideal diode, an always-on LDO, and a 1A buck-boost switching regulator. The entire chip is controlled via direct digital inputs. Designed specifically for USB applications, the PowerPath controller incorporates a precision average input current step-down switching regulator to make maximum use of the allowable USB power. Because power is conserved, the LTC3566 allows the load current on VOUT to exceed the current drawn by the USB port without exceeding the USB load specifications. The PowerPath switching regulator and battery charger communicate to ensure that the input current never violates the USB specifications. The ideal diode from BAT to VOUT guarantees that ample power is always available to VOUT even if there is insufficient or absent power at VBUS. An “always-on” LDO provides a regulated 3.3V from available power at VOUT. Drawing very little quiescent current, this LDO will be on at all times and can be used to supply up to 25mA. The LTC3566 also has a general purpose buck-boost switching regulator, which can be independently enabled via direct digital control. Along with constant frequency PWM mode, the buck-boost regulator has a low power burst-only mode setting for significantly reduced quiescent current under light load conditions. High Efficiency Switching PowerPath Controller Whenever VBUS is available and the PowerPath switching regulator is enabled, power is delivered from VBUS to VOUT via SW. VOUT drives both the external load (including the buck-boost regulator) and the battery charger. If the combined load does not exceed the PowerPath switching regulator’s programmed input current limit, VOUT will track 0.3V above the battery (Bat-Track). By keeping the voltage across the battery charger low, efficiency is optimized because power lost to the linear battery charger is minimized. Power available to the external load is therefore optimized. If the combined load at VOUT is large enough to cause the switching power supply to reach the programmed input current limit, the battery charger will reduce its charge current by the amount necessary to enable the external load to be satisfied. Even if the battery charge current is set to exceed the allowable USB current, the USB specification will not be violated. The switching regulator will limit the average input current so that the USB specification is never violated. Furthermore, load current at VOUT will always be prioritized and only remaining available power will be used to charge the battery. If the voltage at BAT is below 3.3V, or the battery is not present and the load requirement does not cause the switching regulator to exceed the USB specification, VOUT will regulate at 3.6V, thereby providing “Instant-On” operation. If the load exceeds the available power, VOUT will drop to a voltage between 3.6V and the battery voltage. If there is no battery present when the load exceeds the available USB power, VOUT can drop toward ground. The power delivered from VBUS to VOUT is controlled by a 2.25MHz constant-frequency step-down switching regulator. To meet the USB maximum load specification, the switching regulator includes a control loop which ensures that the average input current is below the level programmed at CLPROG. The current at CLPROG is a fraction (hCLPROG–1) of the VBUS current. When a programming resistor and an averaging capacitor are connected from CLPROG to GND, the voltage 3566fa 12 LTC3566 OPERATION on CLPROG represents the average input current of the switching regulator. When the input current approaches the programmed limit, CLPROG reaches VCLPROG, 1.188V and power out is held constant. The input current is programmed by the ILIM0 and ILIM1 pins. It can be configured to limit average input current to one of several possible settings as well as be deactivated (USB Suspend). The input current limit will be set by the VCLPROG servo voltage and the resistor on CLPROG according to the following expression: I VBUS = IBUSQ + VCLPROG •(hCLPROG + 1) RCLPROG 2200 2000 1800 1600 CURRENT (mA) 1400 1200 1000 800 600 400 200 0 0 60 120 180 240 300 360 420 480 FORWARD VOLTAGE (mV) (BAT – VOUT) 3566 F02 VISHAY Si2333 OPTIONAL EXTERNAL IDEAL DIODE LTC3566 IDEAL DIODE ON SEMICONDUCTOR MBRM120LT3 Figure 2. Ideal Diode Operation Figure 1 shows the range of possible voltages at VOUT as a function of battery voltage. 4.5 4.2 3.9 VOUT (V) NO LOAD 3.6 300mV 3.3 3.0 2.7 2.4 2.4 consists of a precision amplifier that enables a large onchip P-channel MOSFET transistor whenever the voltage at VOUT is approximately 15mV (VFWD) below the voltage at BAT. The resistance of the internal ideal diode is approximately 180mΩ. If this is sufficient for the application, then no external components are necessary. However, if more conductance is needed, an external P-channel MOSFET transistor can be added from BAT to VOUT. When an external P-channel MOSFET transistor is present, the GATE pin of the LTC3566 drives its gate for automatic ideal diode control. The source of the external P-channel MOSFET should be connected to VOUT and the drain should be connected to BAT. Capable of driving a 1nF load, the GATE pin can control an external P-channel MOSFET transistor having an on-resistance of 40mΩ or lower. Suspend LDO If the LTC3566 is configured for USB suspend mode, the switching regulator is disabled and the suspend LDO provides power to the VOUT pin (presuming there is power available to VBUS). This LDO will prevent the battery from running down when the portable product has access to a suspended USB port. Regulating at 4.6V, this LDO only becomes active when the switching converter is disabled (suspended). To remain compliant with the USB specification, the input to the LDO is current limited so that it will not exceed the 500μA low power suspend specification. If the load on VOUT exceeds the suspend current limit, the additional current will come from the battery via the ideal diode. 3566fa 2.7 3.0 3.6 3.3 BAT (V) 3.9 4.2 3566 F01 Figure 1. VOUT vs BAT Ideal Diode from BAT to VOUT The LTC3566 has an internal ideal diode as well as a controller for an optional external ideal diode. The ideal diode controller is always on and will respond quickly whenever VOUT drops below BAT. If the load current increases beyond the power allowed from the switching regulator, additional power will be pulled from the battery via the ideal diode. Furthermore, if power to VBUS (USB or wall power) is removed, then all of the application power will be provided by the battery via the ideal diode. The transition from input power to battery power at VOUT will be quick enough to allow only a 10μF capacitor to keep VOUT from drooping. The ideal diode 13 LTC3566 OPERATION TO USB OR WALL ADAPTER 21 VBUS SW 22 SYSTEM LOAD 3.5V TO (BAT + 0.3V) ISWITCH/N PWM AND GATE DRIVE IDEAL DIODE OV VOUT 20 CONSTANT CURRENT CONSTANT VOLTAGE BATTERY CHARGER + – + – GATE 18 OPTIONAL EXTERNAL IDEAL DIODE PMOS 15mV 0.3V 3.6V 2 1.188V AVERAGE INPUT CURRENT LIMIT CONTROLLER AVERAGE OUTPUT VOLTAGE LIMIT CONTROLLER 3566 F03 Figure 3. PowerPath Block Diagram 3.3V Always-On Supply The LTC3566 includes a low quiescent current low dropout regulator that is always powered. This LDO can be used to provide power to a system pushbutton controller, standby microcontroller or real time clock. Designed to deliver up to 25mA, the always-on LDO requires at least a 1μF low impedance ceramic bypass capacitor for compensation. The LDO is powered from VOUT, and therefore will enter dropout at loads less than 25mA as VOUT falls near 3.3V. If the LDO3V3 output is not used, it should be disabled by connecting it to VOUT. VBUS Undervoltage Lockout (UVLO) An internal undervoltage lockout circuit monitors VBUS and keeps the PowerPath switching regulator off until VBUS rises above 4.30V and is about 200mV above the battery voltage. Hysteresis on the UVLO turns off the regulator if VBUS drops below 4.00V or to within 50mV of BAT. When this happens, system power at VOUT will be drawn from the battery via the ideal diode. Battery Charger The LTC3566 includes a constant-current/constant-voltage battery charger with automatic recharge, automatic 14 + + – + – CLPROG +– BAT 19 + SINGLE CELL Li-Ion termination by safety timer, low voltage trickle charging, bad cell detection and thermistor sensor input for out-oftemperature charge pausing. Battery Preconditioning When a battery charge cycle begins, the battery charger first determines if the battery is deeply discharged. If the battery voltage is below VTRKL, typically 2.85V, an automatic trickle charge feature sets the battery charge current to 10% of the programmed value. If the low voltage persists for more than 1/2 hour, the battery charger automatically terminates and indicates via the CHRG pin that the battery was unresponsive. Once the battery voltage is above 2.85V, the battery charger begins charging in full power constant-current mode. The current delivered to the battery will try to reach 1022V/ RPROG. Depending on available input power and external load conditions, the battery charger may or may not be able to charge at the full programmed rate. The external load will always be prioritized over the battery charge current. The USB current limit programming will always be observed and only additional power will be available to charge the battery. When system loads are light, battery charge current will be maximized. 3566fa LTC3566 OPERATION Charge Termination The battery charger has a built-in safety timer. When the voltage on the battery reaches the pre-programmed float voltage of 4.200V, the battery charger will regulate the battery voltage and the charge current will decrease naturally. Once the battery charger detects that the battery has reached 4.200V, the four hour safety timer is started. After the safety timer expires, charging of the battery will discontinue and no more current will be delivered. Automatic Recharge After the battery charger terminates, it will remain off drawing only microamperes of current from the battery. If the portable product remains in this state long enough, the battery will eventually self discharge. To ensure that the battery is always topped off, a charge cycle will automatically begin when the battery voltage falls below 4.1V. In the event that the safety timer is running when the battery voltage falls below 4.1V, it will reset back to zero. To prevent brief excursions below 4.1V from resetting the safety timer, the battery voltage must be below 4.1V for more than 1.3ms. The charge cycle and safety timer will also restart if the VBUS UVLO cycles low and then high (e.g. VBUS, is removed and then replaced) or if the battery charger is cycled on and off by the CHRGEN digital I/O pin. Charge Current The charge current is programmed using a single resistor from PROG to ground. 1/1022th of the battery charge current is sent to PROG which will attempt to servo to 1.000V. Thus, the battery charge current will try to reach 1022 times the current in the PROG pin. The program resistor and the charge current are calculated using the following equations: RPROG = 1022V 1022V ,ICHG = ICHG RPROG In either the constant-current or constant-voltage charging modes, the voltage at the PROG pin will be proportional to the actual charge current delivered to the battery. Therefore, the actual charge current can be determined at any time by monitoring the PROG pin voltage and using the following equation: IBAT = VPROG • 1022 RPROG In many cases, the actual battery charge current, IBAT, will be lower than ICHG due to limited input power available and prioritization with the system load drawn from VOUT. Charge Status Indication The CHRG pin indicates the status of the battery charger. Four possible states are represented by CHRG which include charging, not charging, unresponsive battery and battery temperature out of range. The signal at the CHRG pin can be easily recognized as one of the above four states by either a human or a microprocessor. An open drain output, the CHRG pin can drive an indicator LED through a current limiting resistor for human interfacing or simply a pull-up resistor for microprocessor interfacing. To make the CHRG pin easily recognized by both humans and microprocessors, the pin is either low for charging, high for not charging, or it is switched at high frequency (35kHz) to indicate the two possible faults, unresponsive battery and battery temperature out of range. When charging begins, CHRG is pulled low and remains low for the duration of a normal charge cycle. When charging is complete, i.e., the BAT pin reaches 4.200V and the charge current has dropped to one tenth of the programmed value, the CHRG pin is released (Hi-Z). If a fault occurs, the pin is switched at 35kHz. While switching, its duty cycle is modulated between a high and low value at a very low frequency. The low and high duty cycles are disparate 3566fa 15 LTC3566 OPERATION enough to make an LED appear to be on or off thus giving the appearance of “blinking”. Each of the two faults has its own unique “blink” rate for human recognition as well as two unique duty cycles for machine recognition. The CHRG pin does not respond to the C/10 threshold if the LTC3566 is in VBUS current limit. This prevents false end of charge indications due to insufficient power available to the battery charger. Table 1 illustrates the four possible states of the CHRG pin when the battery charger is active. Table 1. CHRG Output Pin STATUS Charging Not Charging NTC Fault Bad Battery MODULATION (BLINK) FREQUENCY FREQUENCY 0Hz 0Hz 35kHz 35kHz 0Hz (Lo-Z) 0Hz (Hi-Z) 1.5Hz at 50% 6.1Hz at 50% DUTY CYCLE 100% 0% 6.25%, 93.75% 12.5%, 87.5% charge threshold voltage within the bad battery timeout period. In this case, the battery charger will falsely indicate a bad battery. System software may then reduce the load and reset the battery charger to try again. Although very improbable, it is possible that a duty cycle reading could be taken at the bright-dim transition (low duty cycle to high duty cycle). When this happens the duty cycle reading will be precisely 50%. If the duty cycle reading is 50%, system software should disqualify it and take a new duty cycle reading. NTC Thermistor The battery temperature is measured by placing a negative temperature coefficient (NTC) thermistor close to the battery pack. To use this feature connect the NTC thermistor, RNTC, between the NTC pin and ground and a resistor, RNOM, from VBUS to the NTC pin. RNOM should be a 1% resistor with a value equal to the value of the chosen NTC thermistor at 25°C (R25). A 100k thermistor is recommended since thermistor current is not measured by the LTC3566 and will have to be budgeted for USB compliance. The LTC3566 will pause charging when the resistance of the NTC thermistor drops to 0.54 times the value of R25 or approximately 54k. For Vishay “Curve 1” thermistor, this corresponds to approximately 40°C. If the battery charger is in constant-voltage (float) mode, the safety timer also pauses until the thermistor indicates a return to a valid temperature. As the temperature drops, the resistance of the NTC thermistor rises. The LTC3566 is also designed to pause charging when the value of the NTC thermistor increases to 3.25 times the value of R25. For Vishay “Curve 1” this resistance, 325k, corresponds to approximately 0°C. The hot and cold comparators each have approximately 3°C of hysteresis to prevent oscillation about the trip point. Grounding the NTC pin disables the NTC charge pausing function. An NTC fault is represented by a 35kHz pulse train whose duty cycle alternates between 6.25% and 93.75% at a 1.5Hz rate. A human will easily recognize the 1.5Hz rate as a “slow” blinking which indicates the out-of-range battery temperature while a microprocessor will be able to decode either the 6.25% or 93.75% duty cycles as an NTC fault. If a battery is found to be unresponsive to charging (i.e., its voltage remains below 2.85V, for 1/2 hour), the CHRG pin gives the battery fault indication. For this fault, a human would easily recognize the frantic 6.1Hz “fast” blink of the LED while a microprocessor would be able to decode either the 12.5% or 87.5% duty cycles as a bad battery fault. Note that the LTC3566 is a 3-terminal PowerPath product where system load is always prioritized over battery charging. Due to excessive system load, there may not be sufficient power to charge the battery beyond the trickle 3566fa 16 LTC3566 OPERATION Thermal Regulation To optimize charging time, an internal thermal feedback loop may automatically decrease the programmed charge current. This will occur if the die temperature rises to approximately 110°C. Thermal regulation protects the LTC3566 from excessive temperature due to high power operation or high ambient thermal conditions and allows the user to push the limits of the power handling capability with a given circuit board design without risk of damaging the LTC3566 or external components. The benefit of the LTC3566 thermal regulation loop is that charge current can be set according to actual conditions rather than worst-case conditions with the assurance that the battery charger will automatically reduce the current in worst-case conditions. Buck-Boost DC/DC Switching Regulator The LTC3566 contains a 2.25MHz constant-frequency voltage mode buck-boost switching regulator. The regulator provides up to 1A of output load current. The buck-boost can be programmed to a minimum output voltage of 2.75V and can be used to power a microcontroller core, microcontroller I/O, memory, disk drive, or other logic circuitry. To suit a variety of applications, a selectable mode function allows the user to trade off noise for efficiency. Two modes are available to control the operation of the LTC3566’s buck-boost regulator. At moderate to heavy loads, the constant frequency PWM mode provides the least noise switching solution. At lighter loads Burst Mode operation may be selected. The output voltage is programmed by a user supplied resistive divider returned to the FB1 pin. An error amplifier compares the divided output voltage with a reference and adjusts the compensation voltage accordingly until the FB1 has stabilized at 0.8V. The buckboost regulator also includes a soft-start to limit inrush current and voltage overshoot when powering on, short circuit current protection, and switch node slew limiting circuitry for reduced radiated EMI. Input Current Limit The input current limit comparator will shut the input PMOS switch off once current exceeds 2.5A (typical). The 2.5A input current limit also protects against a grounded VOUT1 node. Output Overvoltage Protection If the FB1 node were inadvertently shorted to ground, then the output would increase indefinitely with the maximum current that could be sourced from VIN1. The LTC3566 protects against this by shutting off the input PMOS if the output voltage exceeds a 5.6V (typical). Low Output Voltage Operation When the output voltage is below 2.65V (typical) during start-up, Burst Mode operation is disabled and switch D is turned off (allowing forward current through the well diode and limiting reverse current to 0mA). Buck-Boost Regulator PWM Operating Mode In PWM mode the voltage seen at FB1 is compared to a 0.8V reference. From the FB1 voltage an error amplifier generates an error signal seen at VC1. This error signal commands PWM waveforms that modulate switches A, B, C and D. Switches A and B operate synchronously as do switches C and D. If VIN1 is significantly greater than the programmed VOUT1, then the converter will operate in buck mode. In this mode switches A and B will be modulated, with switch D always on (and switch C always off), to step-down the input voltage to the programmed output. If VIN1 is significantly less than the programmed VOUT1, then the converter will operate in boost mode. In this mode switches C and D are modulated, with switch A always on (and switch B always off), to step-up the input voltage to the programmed output. If VIN1 is close to the programmed VOUT1, then the converter will operate in 4-switch mode. In this mode the switches sequence through the pattern of AD, AC, BD to either step the input voltage up or down to the programmed output. 3566fa 17 LTC3566 OPERATION Buck-Boost Regulator Burst Mode Operation In Burst Mode operation, the buck-boost regulator uses a hysteretic FB1 voltage algorithm to control the output voltage. By limiting FET switching and using a hysteretic control loop, switching losses are greatly reduced. In this mode output current is limited to 50mA typical. While operating in Burst Mode operation, the output capacitor is charged to a voltage slightly higher than the regulation point. The buck-boost converter then goes into a sleep state, during which the output capacitor provides the load current. The output capacitor is charged by charging the inductor until the input current reaches 275mA typical and then discharging the inductor until the reverse current reaches 0mA typical. This process is repeated until the feedback voltage has charged to 6mV above the regulation point. In the sleep state, most of the regulator’s circuitry is powered down, helping to conserve battery power. When the feedback voltage drops 6mV below the regulation point, the switching regulator circuitry is powered on and another burst cycle begins. The duration for which the regulator sleeps depends on the load current and output capacitor value. The sleep time decreases as the load current increases. The maximum load current in Burst Mode operation is 50mA. The buck-boost regulator will not go to sleep if the current is greater than 50mA and if the load current increases beyond this point while in Burst Mode operation the output will lose regulation. Burst Mode operation provides a significant improvement in efficiency at light loads at the expense of higher output ripple when compared to PWM mode. For many noise-sensitive systems, Burst Mode operation might be undesirable at certain times (i.e. during a transmit or receive cycle of a wireless device), but highly desirable at others (i.e. when the device is in low power standby mode). The MODE pin is used to enable or disable Burst Mode operation at any time, offering both low noise and low power operation when they are needed. Buck-Boost Regulator Soft-Start Operation Soft-start is accomplished by gradually increasing the reference voltage input to the error amplifier over a 0.5ms (typical) period. This limits transient inrush currents during start-up because the output voltage is always “in regulation”. Ramping the reference voltage input also limits the rate of increase in the VC1 voltage which helps minimize output overshoot during start-up. A soft-start cycle occurs whenever the buck-boost is enabled, or after a fault condition has occurred (thermal shutdown or UVLO). A soft-start cycle is not triggered by changing operating modes. This allows seamless operation when transitioning between Burst Mode operation and PWM mode. Low Supply Operation The LTC3566 incorporates an undervoltage lockout circuit on VOUT (connected to VIN1) which shuts down the buckboost regulator when VOUT drops below 2.6V. This UVLO prevents unstable operation. Table 2. USB Current Limit Settings ILIM1 0 0 1 1 ILIM0 0 1 0 1 USB SETTING 1x Mode (USB 100mA Limit) 10x Mode (Wall 1A Limit) Suspend 5x Mode (USB 500mA Limit) Table 3. Switching Regulator Modes MODE 0 1 SWITCHING REGULATOR MODE PWM Mode Burst Mode Operation 3566fa 18 LTC3566 APPLICATIONS INFORMATION CLPROG Resistor and Capacitor As described in the High Efficiency Switching PowerPath Controller section, the resistor on the CLPROG pin determines the average input current limit when the switching regulator is set to either the 1x mode (USB 100mA), the 5x mode (USB 500mA) or the 10x mode. The input current will be comprised of two components, the current that is used to drive VOUT and the quiescent current of the switching regulator. To ensure that the USB specification is strictly met, both components of input current should be considered. The Electrical Characteristics table gives values for quiescent currents in either setting as well as current limit programming accuracy. To get as close to the 500mA or 100mA specifications as possible, a 1% resistor should be used. Recall that IVBUS = IVBUSQ + VCLPROG/RCLPROG • (hCLPROG + 1). An averaging capacitor or an R-C combination is required in parallel with the CLPROG resistor so that the switching regulator can determine the average input current. This network also provides the dominant pole for the feedback loop when current limit is reached. To ensure stability, the capacitor on CLPROG should be 0.1μF or larger. Choosing the PowerPath Inductor Because the input voltage range and output voltage range of the PowerPath switching regulator are both fairly narrow, the LTC3566 was designed for a specific inductance value of 3.3μH. Some inductors which may be suitable for this application are listed in Table 4. Table 4. Recommended Inductors for PowerPath Controller INDUCTOR TYPE LPS4018 L (μH) 3.3 MAX IDC (A) 2.2 MAX DCR (Ω) 0.08 SIZE IN mm (L × W × H) MANUFACTURER 3.9 × 3.9 × 1.7 CoilCraft www.coilcraft. com 5.0 × 5.0 × 3.0 Toko 3.8 × 3.8 × 1.8 www.toko.com 4.8 × 4.8 × 1.8 Würth Elektronik www.we-online. com D53LC DB318C WE-TPC Type M1 CDRH6D12 CDRH6D38 3.3 3.3 3.3 2.26 1.55 1.95 0.034 0.070 0.065 3.3 3.3 2.2 3.5 0.0625 6.7 × 6.7 × 1.5 Sumida 0.020 7.0 × 7.0 × 4.0 www.sumida.com 3566fa 19 LTC3566 APPLICATIONS INFORMATION Buck-Boost Regulator Inductor Selection Many different sizes and shapes of inductors are available from numerous manufacturers. Choosing the right inductor from such a large selection of devices can be overwhelming, but following a few basic guidelines will make the selection process much simpler. The buck-boost converter is designed to work with inductors in the range of 1μH to 5μH. For most applications a 2.2μH inductor will suffice. Larger value inductors reduce ripple current which improves output ripple voltage. Lower value inductors result in higher ripple current and improved transient response time. To maximize efficiency, choose an inductor with a low DC resistance. For a 3.3V output, efficiency is reduced about 3% for a 100mΩ series resistance at 1A load current, and about 2% for 300mΩ series resistance at 200mA load current. Choose an inductor with a DC current rating at least 2 times larger than the maximum load current to ensure that the inductor does not saturate during normal operation. If output short circuit is a possible condition, the inductor should be rated to handle the 2.5A maximum peak current specified for the buck-boost converter. Table 5. Recommended Inductors for Buck-Boost Regulator INDUCTOR TYPE LPS4018 D53LC 7440430022 CDRH4D22/HP SD14 L (μH) 3.3 2.2 2.0 2.2 2.2 2.0 MAX IDC (A) 2.2 2.5 3.25 2.5 2.4 2.56 MAX DCR (Ω) 0.08 0.07 0.02 0.028 0.044 0.045 SIZE IN mm (L × W × H) 3.9 × 3.9 × 1.7 3.9 × 3.9 × 1.7 5.0 × 5.0 × 3.0 4.8 × 4.8 × 2.8 4.7 × 4.7 × 2.4 5.2 × 5.2 × 1.45 MANUFACTURER Coilcraft www.coilcraft.com Toko www.toko.com Würth Elektronik www.we-online.com Sumida www.sumida.com Cooper www.cooperet.com Different core materials and shapes will change the size/current and price/current relationship of an inductor. Toroid or shielded pot cores in ferrite or Permalloy materials are small and do not radiate much energy, but generally cost more than powdered iron core inductors with similar electrical characteristics. Inductors that are very thin or have a very small volume typically have much higher core and DCR losses, and will not give the best efficiency. The choice of which style inductor to use often depends more on the price vs size, performance and any radiated EMI requirements than on what the LTC3566 requires to operate. The inductor value also has an effect on Burst Mode operation. Lower inductor values will cause the Burst Mode operation switching frequencies to increase. Table 5 shows several inductors that work well with the LTC3566’s buck-boost regulator. These inductors offer a good compromise in current rating, DCR and physical size. Consult each manufacturer for detailed information on their entire selection of inductors. 3566fa 20 LTC3566 APPLICATIONS INFORMATION VBUS and VOUT Bypass Capacitors The style and value of capacitors used with the LTC3566 determine several important parameters such as regulator control-loop stability and input voltage ripple. Because the LTC3566 uses a step-down switching power supply from VBUS to VOUT, its input current waveform contains high frequency components. It is strongly recommended that a low equivalent series resistance (ESR) multilayer ceramic capacitor be used to bypass VBUS. Tantalum and aluminum capacitors are not recommended because of their high ESR. The value of the capacitor on VBUS directly controls the amount of input voltage ripple for a given load current. Increasing the size of this capacitor will reduce the input voltage ripple. To prevent large VOUT voltage steps during transient load conditions, it is also recommended that a ceramic capacitor be used to bypass VOUT. The output capacitor is used in the compensation of the switching regulator. At least 4μF of actual capacitance with low ESR are required on VOUT. Additional capacitance will improve load transient performance and stability. Multilayer ceramic chip capacitors typically have exceptional ESR performance. MLCCs combined with a tight board layout and an unbroken ground plane will yield very good performance and low EMI emissions. There are several types of ceramic capacitors available, each having considerably different characteristics. For example, X7R ceramic capacitors have the best voltage and temperature stability. X5R ceramic capacitors have apparently higher packing density but poorer performance over their rated voltage and temperature ranges. Y5V ceramic capacitors have the highest packing density, but must be used with caution, because of their extreme nonlinear characteristic of capacitance vs voltage. The actual in-circuit capacitance of a ceramic capacitor should be measured with a small AC signal (ideally less than 200mV) as is expected in-circuit. Many vendors specify the capacitance vs voltage with a 1VRMS AC test signal and as a result overstate the capacitance that the capacitor will present in the application. Using similar operating conditions as the application, the user must measure or request from the vendor the actual capacitance to determine if the selected capacitor meets the minimum capacitance that the application requires. Buck-Boost Regulator Input/Output Capacitor Selection Low ESR MLCC capacitors should be used at both the buck-boost regulator output (VOUT1) and the buck-boost regulator input supply (VIN1). Only X5R or X7R ceramic capacitors should be used because they retain their capacitance over wider voltage and temperature ranges than other ceramic types. A 22μF output capacitor is sufficient for most applications. The buck-boost regulator input supply should be bypassed with a 2.2μF capacitor. Consult with capacitor manufacturers for detailed information on their selection and specifications of ceramic capacitors. Many manufacturers now offer very thin (96%, Accurate USB Current Limiting (500mA/100mA), 4mm × 4mm QFN-24 Package VIN: 2.4V to 5.5V, VOUT: 1.8V to 5.25V IQ = 35μA, 2mm × 3mm DFN-8 Package Synchronous Buck Converter, Efficiency: 93%, Adjustable Output at 600mA; Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power Detection and Selection, 3mm × 5mm DFN-16 Package Synchronous Buck Converter, Efficiency: 93%, Output: 1.875V at 600mA; Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power Detection and Selection, 3mm × 5mm DFN-16 Package Synchronous Buck Converter, Efficiency: >90%, Adjustable Outputs at 800mA and 400mA; Charge Current Programmable Up to 950mA, USB Compatible, 3mm × 5mm DFN-16 Package Synchronous Buck Converter, Efficiency: >90%, Output: 1.8V at 800mA, 1.575V at 400mA; Charge Current Programmable Up to 950mA, USB Compatible, 3mm × 5mm DFN-16 Package Complete Multi-Function PMIC: Switchmode Power Manager and Three Buck Regulators Plus LDO; Charge Current Programmable Up to 1.5A from Wall Adapter Input, Thermal Regulation, Synchronous Buck Converters Efficiency: >95%, ADJ Outputs: 0.8V to 3.6V at 400mA/400mA/1A Bat-Track Adaptive Output Control, 200mΩ Ideal Diode, 4mm × 5mm QFN-28 Package Complete Multi-Function PMIC: Switching Power Manager, 1A Buck-Boost + 2 Buck Regulators + LDO, ADJ Out Down to 0.8V at 400mA/400mA/1A, Synchronous Buck/ Buck-Boost Converter Efficiency: >95%; Charge Current Programmable up to 1.5A from Wall Adapter Input, Thermal Regulation, Bat-Track Adaptive Output Control, 180mΩ Ideal Diode, 4mm × 5mm QFN-28 Package Complete Multi-Function PMIC: Linear Power Manager and Three Buck Regulators, Charge Current Programmable Up to 1.5A from Wall Adapter Input, Thermal Regulation, Synchronous Buck Converters Efficiency: >95%, ADJ Output: 0.8V to 3.6V at 400mA/ 400mA/600mA, Bat-Track Adaptive Output Control, 200mΩ Ideal Diode, 4mm × 4mm QFN-28 Package Adjustable Synchronous Buck Converters, Efficiency: >90%, Outputs: Down to 0.8V at 400mA for Each, Charge Current Programmable Up to 950mA, USB Compatible, 3mm × 3mm QFN-16 Package Charges Single-Cell Li-Ion Batteries Directly From USB Port, Thermal Regulation, 4mm × 4mm QFN-16 Package 13V Overvoltage Transient Protection, Thermal Regulation 200mΩ Ideal Diode with