ltc3552 Linear Technology Corporation, ltc3552 Datasheet
ltc3552
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ltc3552 Summary of contents
Page 1
... When the input supply (wall adapter or USB supply) is removed, the LTC3552 enters a low current state dropping the battery drain current to less than 2µA. Thermal regula- tion maximizes charge rate without risk of overheating. ...
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... T JMAX EXPOSED PAD IS GROUND (PIN 17) ORDER PART NUMBER LTC3552EDHC Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. ...
Page 3
... MODE/SYNC = 0. 3V 0.5V, Duty Cycle < 0.5V, Duty Cycle < 35 (Note 6) (Note 5V 0V RUN FB V Ramping Down, MODE/SYNC = 0V FB LTC3552 MIN TYP MAX UNITS ● 0.4 0.7 V ● 0 ● 1 MΩ 70 100 140 ● ...
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... Maximum Rating condition for extended periods may affect device reliability and lifetime. Pins of regulators should not exceed 6V. Note 2: The LTC3552E 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 ...
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... IN 600 PROG 500 400 300 200 = 10k PROG 100 0 6 6.5 7 7.5 8 –50 V (V) IN 3552 G10 LTC3552 T = 25°C Unless Otherwise Specifi ed. A Charge Current vs Battery Voltage 600 500 400 300 200 100 IN θ = 40°C PROG ...
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... LTC3552 W U TYPICAL PERFOR A CE CHARACTERISTICS Battery Charger Power FET On-Resistance vs Temperature 700 100mA BAT 650 PROG 600 550 500 450 400 350 –50 – TEMPERATURE (°C) Switching Regulator Burst Mode Operation SW 5V/DIV I L 200mA/ DIV V OUT RIPPLE ...
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... 1.5V, REGULATOR 1 OUT Burst Mode OPERATION, MODE/SYNC = 3. LOAD ON OTHER REGULATOR CIRCUIT OF FIGURE 100 1000 LOAD CURRENT (mA) 3552 G27 LTC3552 R vs Junction Temperature DS(ON) 550 V = 2.7V CC 500 4.2V 450 CC 400 350 300 250 200 150 MAIN SWITCH ...
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... LTC3552 CTIO S ITERM (Pin 1): Charge Termination Program. The charge termination current threshold is programmed by connect- ing a 1% resistor ground. The current threshold TERM ITERM, is set by the following formula: 100 V 100 = = TERM TERM R I TERM TERM BAT (Pin 2): Charge Current Output. Provides charge cur- rent to the battery from the internal P-channel MOSFET, and regulates the fi ...
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... I TH BURST I COMP + 0.35V LATCH R Q SWITCHING UV LOGIC AND BLANKING ANTI CIRCUIT SHOOT- THRU OV I RCMP PGOOD1 POR COUNTER OSC PGOOD2 LTC3552 IN 1000× + BAT 2 5µ – REF 1.21V 1V R4 0.1V R5 ITERM 1 PROG 13 R PROG GND 17 BURST V CC CLAMP + 5Ω ...
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... LTC3552 U OPERATIO The LTC3552 is made up of two parts: a standalone constant-current/constant-voltage linear charger for a single-cell lithium-ion battery and a high effi ciency dual DC/DC switching regulator. The charger can deliver up to 950mA of charge current (using a good thermal PCB lay- out) with a fi nal fl oat voltage accuracy of ±1%. An internal P-channel power MOSFET and thermal regulation circuitry are included ...
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... For highest effi ciency at low current, connecting the MODE/SYNC pin to V lator operate in Burst Mode, where the PMOS switch operates intermittently based on load demand with a LTC3552 voltage, which is the voltage decreases FB makes the regu- ...
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... LTC3552 U OPERATIO fi xed peak inductor current. By running cycles periodically, the switching losses which are dominated by the gate charge losses of the power MOSFETs are minimized. The main control loop is interrupted when the output voltage reaches the desired regulated value. A voltage comparator trips when I is below 0 ...
Page 13
... I TERM current is set by the equation CHG , from * Any external sources that hold the ITERM pin above 100mV will prevent the LTC3552 TERM from terminating a charge cycle. ** These equations apply only when the ITERM pin is shorted to the PROG pin. LTC3552 V RUN1 IN 1µ ...
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... The choice of which style inductor to use often depends more on the price vs size requirements and any radiated fi eld/EMI requirements than on what the LTC3552 requires to operate. Table 1 shows some typical surface mount inductors that work well in LTC3552 applications. ...
Page 15
... Q of ceramic capacitors along with trace inductance can ⎠ ⎟ lead to signifi cant ringing. In most cases, 0.1µF to 1µF of X5R dielectric ceramic capacitors should also be placed = output capacitance close to the LTC3552 in parallel with the main capacitors for high frequency decoupling. LTC3552 increases L = 0.3 • ...
Page 16
... LTC3552 U U APPLICATIO S I FOR ATIO Ceramic Input and Output Capacitors Higher value, lower cost ceramic capacitors are now be- coming available in smaller case sizes. These are tempting for switching regulator use because of their very low ESR. Unfortunately, the ESR is so low that it can cause loop stability problems. Solid tantalum capacitor ESR generates a loop “ ...
Page 17
... Effi ciency = 100% – ( ...) where L1, L2, etc. are the individual losses as a percent- age of input power. Although all dissipative elements in the circuit produce losses, four main sources usually account for most of the losses in LTC3552 circuits switching losses losses, 4) other losses. ...
Page 18
... 120°C – 54.4° 65.6°C A The LTC3552 can be used above 65°C ambient but the charge current will be reduced from the programmed 800mA. The approximate current at a given ambient temperature can be approximated by BAT Using the previous example with an ambient temperature of 70° ...
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... As an example, a correctly soldered LTC3552 can deliver over 800mA to a battery from a 5V supply at room temperature. Without a good backside thermal connection, this number will drop considerably. ...
Page 20
... Figure 4. Low Loss Input Reverse Polarity Protection Design Example As a design example, assume the LTC3552 is used in a single lithium-ion battery-powered cellular phone ap- plication. Starting with the charger, choosing R programs the charger for 806mA. A good rule of thumb for I is one tenth the full charge current TERMINATE is picked ...
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... APPLICATIO S I FOR ATIO Board Layout Considerations When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3552. These items are also illustrated graphically in the layout diagram of Figure 5. Check the following in your layout: 1. Does the capacitor C ...
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... LTC3552 TYPICAL APPLICATION 1µF V OUT2 2.5V/400mA C OUT2 4.7µF CER 22 Full-Featured Single-Cell Li-Ion Charger Plus Dual Step-Down Converter LTC3552 RUN1 V IN RUN2 1k BAT CHRG PWR MODE/SYNC EN 100k POR 4.7µH 2.2µH SW2 SW1 FF2 68pF 887k 604k V V FB2 ...
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... Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) 0.65 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 4.40 ±0.05 (2 SIDES) 5.00 ±0.10 (2 SIDES 0.20 TYP 1.65 ± 0.10 3.00 ±0.10 (2 SIDES) (2 SIDES) 0.75 ±0.05 0.00 – 0.05 LTC3552 R = 0.115 0.40 ± 0.10 TYP 9 16 PIN 1 NOTCH (DHC16) DFN 1103 8 1 0.25 ± 0.05 0.50 BSC 4.40 ±0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD 23 3552f ...
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... LTC4412 Low-Loss PowerPath PowerPath and ThinSOT are registered trademarks of Linear Technology Corporation. Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● RUN1 RUN2 LTC3552 1k CHRG BAT 1k PWR POR EN MODE/SYNC 4.7µH 2.2µH SW2 SW1 C FF2 ...