ltc3523-ltc3523-2 Linear Technology Corporation, ltc3523-ltc3523-2 Datasheet
ltc3523-ltc3523-2
Related parts for ltc3523-ltc3523-2
ltc3523-ltc3523-2 Summary of contents
Page 1
... The LTC3523/LTC3523-2 provide a sub-2μA shutdown mode, overtemperature shutdown and current limit pro- tection on both converters. The LTC3523/LTC3523-2 are housed in a 16-lead 3mm × 3mm × 0.75mm QFN package. , LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. ...
Page 2
... The denotes the specifi cations which apply over the full operating = 25° 2.4V IN1 IN2 IN3 CONDITIONS I = 1mA LOAD LTC3523 LTC3523 0V 0V ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 1 ⎯ S ⎯ H ⎯ D ⎯ N ⎯ 2 OUT IN1 IN2 Measured from ...
Page 3
... FB2 to the output of the error amplifi er. Note 6: Specifi cation is guaranteed by design and not 100% tested in production. Note 7: Current measurements are performed when the LTC3523/ LTC3523-2 are not switching. The current limit values in operation will be somewhat higher due to the propagation delay of the comparator. LTC3523/LTC3523-2 = 3.3V ...
Page 4
... LTC3523/LTC3523-2 TYPICAL PERFORMANCE CHARACTERISTICS Normalized FBx Reference vs Temperature 1.00125 1.00000 0.99875 0.99750 0.99625 0.99500 –45 –25 – TEMPERATURE (°C) 3523 G01 Inrush Current Control for the Step-Down Converter V OUT_BCK 1V/DIV I L_BCK 200mA/DIV SHDN2 2V/DIV 3523 G04 V = 1.2V 200μs/DIV ...
Page 5
... Step-Up Converter Output Voltage Sense Input OUT and Drain of the Internal Synchronous Rectifi er MOSFET. Driver bias is derived from the output fi lter capacitor(s) should be as short OUT and wide as possible. . This IN2 LTC3523/LTC3523 25°C unless otherwise noted) A Mode Transition Response V OUT_BST 50mV/DIV V OUT_BCK ...
Page 6
... LTC3523/LTC3523-2 PIN FUNCTIONS SW1 (Pin 5): Step-Up Converter Switch Pin. Connect the inductor between SW1 and V . Keep these PCB trace IN1 lengths as short and wide as possible to reduce EMI and voltage overshoot. If the inductor current falls to zero or ⎯ S ⎯ H ⎯ D ⎯ N ⎯ low, an internal 100Ω anti-ringing switch is connected from SW1 minimize EMI ...
Page 7
... LIM + REF – – MODE DRIVERS OSC – FB2 + 0.6V –9% SHUTDOWN AND SHDN V BIAS GND1 GND2 GND3 LTC3523/LTC3523-2 BULK CONTROL SIGNALS V V OUT OUT 4 STEP-UP 1.8V TO 5.25V + – I ZERO COMP MODE MODE R1 FB1 C + OUT 1 10μF – R2 1.2V g ERROR ...
Page 8
... The soft-start function resets in the event of a commanded shutdown or thermal shutdown. Oscillator The frequency of operation is set by an internal oscilla- tor to a nominal 1.2MHz for the LTC3523 and nominal 2.4MHz for the LTC3523-2. The oscillator is shared by both converters. Shutdown The step-up and the step-down converters have inde- pendent shutdown pins ...
Page 9
... COMPONENT SELECTION Inductor Selection The LTC3523/LTC3523-2 can utilize small surface mount and chip inductors due to its fast 1.2MHz switching frequency and for the 2.4MHz version, the values are halved. The Inductor current ripple is typically set for ...
Page 10
... Molded chokes and some chip inductors usually do not have enough core to support the peak inductor currents of 1000mA seen on the LTC3523/LTC3523-2. To minimize radiated noise, use a toroid, pot core or shielded bobbin inductor. See Table 1 for suggested inductors and suppliers. ...
Page 11
... This can be accomplished by taking advantage of the large thermal pad on the underside of the LTC3523/LTC3523- recom- mended that multiple vias in the printed circuit board be used to conduct heat away from the LTC3523/LTC3523-2 and into the copper plane with as much area as possible ...
Page 12
... LTC3523/LTC3523-2 APPLICATIONS INFORMATION DUAL BUCK-BOOST AND STEP-UP CONVERTER OPERATION The LTC3523/LTC3523-2 can be operated in a cascaded confi guration as shown in Figure 2, allowing buck-boost and step-up converter operation. Supply rail sequencing is achieved by feeding the step-up converter PGOOD1 V IN 1.8V TO 5.25V V OUT1 STEP-UP OUTPUT 5V 10μF ...
Page 13
... SW2 V FB2 OUT LTC3523 FB1 MODE 634k PGOOD1 PGOOD2 SHDN1 SHDN2 365k GND1 GND2 GND3 V OUT1 2V/DIV PGOOD2 V OUT2 1V/DIV SHDN2 500μs/DIV LTC3523/LTC3523-2 V OUT2 STEP-DOWN OUTPUT 1.2V 10pF 511k 10μF 200mA 511k 100k V IN OFF ON 3523 TA02a 3523 TA02b 3523f 13 ...
Page 14
... Li-Ion to 5V/150mA, 2.5V/200mA 4.7μF 10μ 4.7μH IN1 IN2 BAT SW1 SW2 V FB2 OUT LTC3523 FB1 MODE V 768k IN PGOOD1 PGOOD2 SHDN1 SHDN2 243k GND1 GND2 GND3 OFF ON Effi ciency and Power Loss vs Load Current 100 EFFICIENCY 90 80 ...
Page 15
... Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 0.75 ± 0.05 (4 SIDES) 1.45 ± 0.10 (4-SIDES) 0.200 REF 0.00 – 0.05 LTC3523/LTC3523-2 BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP R = 0.115 OR 0.25 × 45° CHAMFER TYP 15 16 0.40 ± 0. (UD16) QFN 0904 0.25 ± 0.05 ...
Page 16
... LTC3523/LTC3523-2 RELATED PARTS PART NUMBER DESCRIPTION LTC3400/LTC3400B 600mA (I ), 1.2MHz, Synchronous Step-Up DC/DC Converters SW LTC3401 3MHz, Synchronous Step-Up DC/DC Converter SW LTC3402 3MHz, Synchronous Step-Up DC/DC Converter SW LTC3421 3MHz, Synchronous Step-Up DC/DC Converter SW with Output Disconnect Converter LTC3422 1. 3MHz, Synchronous Step-Up DC/DC with Output SW Disconnect Converter ...