LTC3554 LINER [Linear Technology], LTC3554 Datasheet
LTC3554
Available stocks
Related parts for LTC3554
LTC3554 Summary of contents
Page 1
... The LTC3554 also includes two synchronous step-down switching regulators as well as a pushbutton controller. With all supplies enabled in standby mode, the quiescent current drawn from the battery is only 10μA. The LTC3554 is available in a 3mm × 3mm × 0.55mm 20-pin UTQFN package. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation ...
Page 2
... ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL LTC3554EPD#PBF LTC3554EPD#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: For more information on tape and reel specifi ...
Page 3
... Rising NTC Voltage Hysteresis Hysteresis Falling NTC Voltage Hysteresis NTC BUS (Note 12 200mA OUT BUS (Note 5mA CHRG V = 4.5V CHRG BAT LTC3554 = 25°C, A MIN TYP MAX 3.8 3.9 3.5 3.6 200 300 0 50 350 4.179 4.2 4.221 4.165 4.2 4.235 380 400 420 1 ...
Page 4
... LTC3554 SWITCHING REGULATOR ELECTRICAL CHARACTERISTICS l The denotes specifi cations that apply over the full operating temperature range, otherwise specifi cations are BVIN = 3.8V, PWR_ON1 = PWR_ON2 = 0V, unless otherwise noted. OUT SYMBOL PARAMETER BVIN Input Supply Voltage V UVLO V Falling OUT OUT ...
Page 5
... All Enabled Bucks within PGOOD Threshold Voltage All Bucks Disabled Note 2. The LTC3554 is guaranteed to meet performance specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. ...
Page 6
... LTC3554 ELECTRICAL CHARACTERISTICS Note 3. This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperatures will exceed 110°C when overtemperature protection is active. Continuous operation above the specifi ed maximum operating junction temperature may result in device degradation or failure. ...
Page 7
... OUT 0 I BUS 0A 0.5A/DIV I 0A BAT 0.5A/DIV 1ms/DIV V = 3.75V BAT I = 100mA OUT PROG LTC3554 T = 25°C, unless otherwise specifi ed. A Battery Charge Current and Voltage vs Time 600 920mAhr CELL CHRG BUS R = 1.87k 500 PROG V BAT 400 300 SAFETY TIMER ...
Page 8
... LTC3554 TYPICAL PERFORMANCE CHARACTERISTICS Switching from 100mA Mode to 500mA Mode 5V HPWR 0 I BUS 0.5A/DIV 0A I BAT 0.5A/DIV 0A 3554 G14 1ms/DIV V = 3.75V BAT I = 50mA OUT PROG Step-Down Switching Regulator 1 3.3V Output Effi ciency vs I OUT1 100 FSEL = L 90 STBY = ...
Page 9
... V OUT2 50mV/DIV (AC) V OUT1 1V/DIV 100mA/DIV 0mA PWR_ON1 100 1000 3554 G21 LTC3554 T = 25°C, unless otherwise specifi ed. A Step-Down Switching Regulator Output Transient 50μs/DIV 3554 G26 V = 1.2V OUT2 STBY = H Step-Down Switching Regulator Switch Impedance vs Temperature BV = 3.2V IN STBY = L ...
Page 10
... LTC3554 TYPICAL PERFORMANCE CHARACTERISTICS Step-Down Switching Regulator Output Transient (FSEL Low to High) V OUT1 50mV/DIV (AC) V OUT2 20mV/DIV (AC) FSEL 50μs/DIV 3554 G29 V = 3.3V OUT1 I = 100mA OUT1 V = 1.2V OUT2 I = 50mA OUT2 STBY = Step-Down Switching Regulator Output Transient (STBY High to Low) V OUT1 20mV/DIV (AC) ...
Page 11
... V OUT diode or be charged from the battery charger. V (Pin 18): Output Voltage of the PowerPath Controller OUT and Input Voltage of the Battery Charger. The majority of the portable products should be powered from V LTC3554 through the ideal . The OUT 3554f 11 ...
Page 12
... LTC3554 PIN FUNCTIONS LTC3554 will partition the available power between the external load on V and the internal battery charger. OUT Priority is given to the external load and any extra power is used to charge the battery. An ideal diode from BAT to V ensures that V is powered even if the load exceeds ...
Page 13
... PWR_ON1 9 PWR_ON2 8 PBSTAT INPUT CC/CV CURRENT CHARGER LIMIT EXTPWR UVLO OSC 0.8V EN STBY 200mA STEP-DOWN DC/DC OSC 0.8V EN STBY 200mA STEP-DOWN DC/DC PUSH BUTTON POWER GOOD INTERFACE COMPARATORS 21 GND LTC3554 18 V OUT BAT 17 16 PROG SW1 13 FB1 6 BVIN 12 SW2 11 FB2 7 4 PGOOD 3554 BD1 3554f 13 ...
Page 14
... USB PowerPath Controller The input current limit and charger control circuits of the LTC3554 are designed to limit input current as well as control battery charge current as a function of I drives the combination of the external load, the two step- down switching regulators and the battery charger ...
Page 15
... OPERATION Ideal Diode From BAT to V OUT The LTC3554 has an internal ideal diode from BAT to V designed to respond quickly whenever V BAT. If the load increases beyond the input current limit, additional current will be pulled from the battery via the ideal diode. Furthermore, if power to V ...
Page 16
... CHRG pin is released (high impedance). The CHRG pin does not respond to the C/10 threshold if the LTC3554 reduces the charge current due to excess load on the V of charge indications due to insuffi cient power available to the battery charger ...
Page 17
... NOM value of the chosen NTC thermistor at 25°C (R25). The LTC3554 will pause charging when the resistance of the NTC thermistor drops to 0.54 times the value of R25 or approximately 54k (for a Vishay curve 1 thermistor, this corresponds to approximately 40°C). If the battery ...
Page 18
... Ratio of R HOT NTC|HOT R = Primary thermistor bias resistor (see Figure 2) NOM R1 = Optional temperature range adjustment resistor (see Figure 2) The trip points for the LTC3554’s temperature qualifi ca- tion are internally programmed at 0.35 • V threshold and 0.76 • BUS 20 R NOM 105k ...
Page 19
... R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k The nearest 1% value is 12.7k. The fi nal solution is shown in Figure 2 and results in an upper trip point of 45°C and a lower trip point of 0°C. LTC3554 is 0.2488 HOT should be set NOM , the cold trip point is ...
Page 20
... Burst Mode operation to maintain high effi ciency. Applications with a near-zero-current sleep or memory keep-alive mode can command the LTC3554 switching regulators into a standby mode that maintains output regulation while drawing only 1.5μA quiescent current per active regulator. Load capability drops to 5mA per regulator in this mode ...
Page 21
... The application circuit commands the LTC3554 into and out of standby mode via the STBY pin logic input. Bringing the STBY pin high places both regulators into standby mode, while bringing it low returns them to Burst Mode operation ...
Page 22
... LTC3554 OPERATION In standby mode, each regulator operates hysteretically. When the FB pin voltage falls below the internal 0.8V reference, a current source from BVIN to SW turns on, delivering current through the inductor to the switching regulator output capacitor and load. When the FB pin voltage rises above the reference plus a small hysteresis voltage, that current is shut off ...
Page 23
... FSEL = L FSEL = H 0 100 1000 Figure 5. 3.3V Output Effi ciency and Power Loss LTXXXX GXX vs Load Current LTC3554 OUT 1000 BAT = 3.8V 100 EFFICIENCY 10 POWER LOSS 1 0.1 FSEL = L FSEL = 0.01 0 100 1000 LOAD CURRENT (mA) LTXXXX GXX ...
Page 24
... LTC3554 OPERATION Inductor value should be chosen based on the desired output voltage. See Table 2. Table 3 shows several inductors that work well with the step-down switching regulators. 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 ...
Page 25
... Many manufacturers now offer very thin (<1mm tall) ceramic capacitors ideal for use in height-restricted designs. Table 1 shows a list of several ceramic capacitor manufacturers. PUSHBUTTON INTERFACE State Diagram/Operation Figure 6 shows the LTC3554 pushbutton state diagram. HR PUP2 EXTPWR OR PB400MS PUP1 ...
Page 26
... PON state, without passing through the power-up (PUP1 or PUP2) states. This is because by asserting logic high on the PWR_ON1 or PWR_ON2 pins, the application has already told the LTC3554 exactly which buck(s) to turn on, so there is no need for an intermediate PUP state in which both bucks are enabled for fi ve seconds. ...
Page 27
... PWR_ON1 PWR_ON2 STATE Power-Up Via Pushbutton Press Figure 7 shows the LTC3554 powering up through ap- plication of the external pushbutton. For this example the pushbutton circuitry starts in the POFF or HR state with a battery connected and both bucks disabled. Pushbutton application (ON low) for 400ms transitions the pushbutton circuitry into the PUP state and powers up buck1 followed by buck2 ...
Page 28
... PBSTAT does not go low on initial pushbutton application for power-up, but will go low with subsequent ON pushbut- ton applications in the PUP1, PUP2 or PON states. Power-Up Via Applying External Power Figure 8 shows the LTC3554 powering up through ap- plication of external power (V ). For this example the BUS pushbutton circuitry starts in the POFF or HR state with a battery connected and both bucks disabled ...
Page 29
... POFF state. During this one second time, the ON and PWR_ON inputs as well as external power application are ignored to allow all LTC3554 generated supplies to go low. Though the above assumes a battery present, the same operation would take place with a valid external supply (V or without a battery present ...
Page 30
... HR state. Under these conditions an 5s explicit power up event (such as a pushbutton press) may be required to bring the LTC3554 out of hard reset. Hard Reset Timing HARD RESET provides an ultralow power-down state for shipping or long term storage as well as a way to power down the application in case of a software lockup ...
Page 31
... Exposed Pad on the backside of the package and an adequately sized ground plane will result in thermal resistances far greater than 70°C/W. The conditions that cause the LTC3554 to reduce charge current due to the thermal protection feedback can be approximated by considering the power dissipated in the part ...
Page 32
... T = 110°C – 0.98W • 70°C/W = 41.4°C A The LTC3554 can be used above 41.4°C, but the charge current will be reduced below 400mA. The charge current at a given ambient temperature can be approximated by (110°C – θ ...
Page 33
... FSEL FB1 R LO1 STBY 649k L2 PGOOD 10μH 11 1.2V PWR_ON2 SW2 C5 R UP2 PBSTAT 10pF 332k 7 ON FB2 GND R LO2 649k R2 100k LTC3554 LDO 1.8V EN MEMORY I/O C4 10μF CORE C6 10μF μC R3 100k PBSTAT PWR_ON2 PGOOD STBY FSEL PWR_ON1 SUSP HPWR 3554 F14 33 3554f ...
Page 34
... LTC3554 TYPICAL APPLICATION 4.35V TO 5.5V USB INPUT Figure 15. 3-Cell Alkaline/Lithium with PowerPath (Charger Disabled SYSTEM LOAD BUS OUT 15 14 CHRG NTC LTC3554 17 BAT 16 + PROG R PROG 1.87k 12 1 BVIN HPWR C2 19 SUSP 2.2μF L1 10μ PWR_ON1 SW1 C3 10pF 2 6 FB1 ...
Page 35
... Plastic UTQFN (3mm × 3mm) (Reference LTC DWG # 05-08-1835 Rev Ø) 0.70 ±0.05 1.65 ±0.05 PACKAGE OUTLINE 0.20 ±0.05 0.40 BSC 0.55 ± 0.05 3.00 ± 0. 0.05 TYP 1.60 REF 0.150 REF 0.00 – 0.05 LTC3554 BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH 0.35 45° 0.10 CHAMFER TYP 19 20 0.40 ± 0. 1.65 ±0.10 1.65 ±0.10 (PD20) UTQFN 0409 REV Ø 0.20 ± 0.05 ...
Page 36
... LTC3554 RELATED PARTS PART DESCRIPTION NUMBER LTC3455 Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger LTC3456 2-Cell, Multioutput DC/DC Converter with USB Power Manager LTC3550 Dual Input USB/AC Adapter Li-Ion Battery Charger with Adjustable Output 600mA Buck Converter LTC3552 Standalone Linear Li-Ion Battery Charger ...