Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Switched-capacitor voltage converter MSOP 12 EP

LTC3245

3245fa

For more information www.linear.com/LTC3245

Typical applicaTion

FeaTures DescripTion

Wide V

Range,

Low Noise, 250mA Buck-Boost

Charge Pump

The LTC

3245 is a switched capacitor buck-boost DC/DC

converter that produces a regulated output (3.3V, 5V or

justable) from a 2.7V to 38V input. The device uses

switched capacitor fractional conversion to maintain

regulation over a wide range of input voltage. Internal

circuitry automatically selects the conversion ratio to

optimize efficiency as input voltage and load conditions

vary. No inductors are required.

The unique constant frequency architecture provides a

lower noise output than conventional charge pump regu

lators. To optimize efficiency at the expense of slightly

higher output ripple, the device has pin selectable Burst

Mode operation.

Low operating current (20μA with no load, 4μA in shut

down) and low external parts count (three small ceramic

pacitors) make the LTC3245 ideally suited for low power,

space constrained automotive/industrial applications. The

device is short-circuit and overtemperature protected, and

is available in thermally enhanced 12-pin MSOP and low

profile 3mm × 4mm 12-pin DFN packages.

Efficient Regulated 5V Output

applicaTions

Automotive ECU/CAN Transceiver Supplies

Industrial Housekeeping Supplies

Low Power 12V to 5V Conversion

L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks

and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

OUT

Efficiency vs Output Current

2.7V to 38V V

Range

= 18µA Operating; 4μA in Shutdown

12V to 5V Efficiency = 81%

Multimode Operation (2:1, 1:1, 1:2) with Automatic

Mode Switching

Low Noise, Constant Frequency Operation

Pin Selectable Burst Mode

Operation

OUT

: Fixed 3.3V, 5V or Adjustable (2.5V to 5V)

OUT

Up to 250mA

Overtemperature and Short-Circuit Protection

Operating Junction Temperature: 150°C Maximum

Thermally Enhanced 12-Pin MSOP and Low Profile

12-Pin (3mm × 4mm) DFN Packages

OUT

(mA)

EFFICIENCY (%)

LOSS

(mW)

3245 TA01b

400

300

250

350

200

100

150

0.1 100 1000101

EFFICIENCY

LOSS

= 12V

–

SEL2

BURST

SEL1

OUT

OUTS/ADJ

PGOOD

GND

LTC3245

= 2.7V TO 38V

OUT

= 5V

OUT

UP TO 250mA

3245 TA01a

1µF

10µF

500k

Summary of content (18 pages)

PAGE 1
LTC3245 Wide VIN Range, Low Noise, 250mA Buck-Boost Charge Pump Description Features n n n n n n n n n n n 2.7V to 38V VIN Range IQ = 18µA Operating; 4μA in Shutdown 12V to 5V Efficiency = 81% Multimode Operation (2:1, 1:1, 1:2) with Automatic Mode Switching Low Noise, Constant Frequency Operation Pin Selectable Burst Mode® Operation VOUT: Fixed 3.3V, 5V or Adjustable (2.
PAGE 2
LTC3245 Absolute Maximum Ratings (Note 1) VIN, SEL1, SEL2, BURST............................. –0.3V to 38V VOUT, OUTS/ADJ, PGOOD............................. –0.3V to 6V IPGOOD.......................................................................2mA VOUT Short-Circuit Duration.............................. Indefinite Operating Junction Temperature Range (Notes 2, 3) (E-/I-Grade)......................................... –40°C to 125°C (H-Grade)............................................
PAGE 3
LTC3245 Electrical Characteristics The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C, (Note 2). VIN = 12V, VOUT = 5V, CFLY = 1µF unless otherwise noted.
PAGE 4
LTC3245 Typical Performance Characteristics Input Operating Current vs Input Voltage Input Shutdown Current vs Input Voltage 500 475 40 16 35 14 30 12 ISD (µA) VOUT = 5V 20 VOUT = 3.3V 15 10 6 4 5 2 0 0 5 10 15 20 25 VIN (V) 125°C 8 10 30 35 0 40 450 150°C 25°C –55°C 0 5 10 15 20 25 VIN (V) 30 5.15 5.15 5.10 5.10 4.80 IOUT = 150mA IOUT = 0mA 5.00 IOUT = 150mA IOUT = 250mA 4.90 IOUT = 250mA 4.80 2 3 4 5 6 7 8 9 10 11 12 13 14 15 VIN (V) 3.50 3.45 3.45 3.
PAGE 5
LTC3245 Typical Performance Characteristics TA = 25°C, unless otherwise noted. 3.3V Fixed Output Voltage vs Falling Input Voltage (Burst Mode Operation) 5V Fixed Output Voltage vs Falling Input Voltage (Burst Mode Operation) ADJ Regulation Voltage vs Temperature 5.100 3.400 1.220 5.075 3.375 1.215 IOUT = 1mA 5.050 3.350 5.025 1.205 4.975 IOUT = 250mA 4.950 3.300 3.275 2 3 4 5 6 7 8 9 10 11 12 13 14 15 VIN (V) 3.
PAGE 6
LTC3245 Typical Performance Characteristics 3.3V Output Transient Response 5V Output Transient Response Burst Mode OPERATION AC 50mV/DIV Burst Mode OPERATION AC 50mV/DIV LOW NOISE AC 50mV/DIV LOW NOISE AC 50mV/DIV 200mA IOUT 5mA 3245 G19 VIN = 12V VOUT = 5V TA = 25°C, unless otherwise noted. 150mA IOUT 5mA 3245 G20 VIN = 12V VOUT = 3.3V 3245fa 6 For more information www.linear.
PAGE 7
LTC3245 Pin Functions VIN (Pins 1, 2, 3): Power Input Pins. Input voltage for both charge pump and IC control circuitry. The VIN pin operates from 2.7V to 38V. All VIN pins should be connected together at pins. BURST (Pin 4): Burst Mode Logic Input. A logic high on the BURST pin operates the charge pump in low noise constant frequency. A logic low will operates the charge pump in Burst Mode operation for higher efficiency at low output currents.
PAGE 8
LTC3245 Simplified Block Diagram C+ C– CHARGE PUMP VIN VOUT EN BURST BURST DETECTED OVERTEMPERATURE OUTS/ADJ ADJ 3.3V MUX – + PGOOD 1.2V – 1.14V 5V SD + SEL1 SEL2 GND 3245 BD 3245fa 8 For more information www.linear.
PAGE 9
LTC3245 Applications Information General Operation The LTC3245 uses switched capacitor based DC/DC conversion to provide the efficiency advantages associated with inductor based circuits as well as the cost and simplicity advantages of a linear regulator. The LTC3245’s unique constant frequency architecture provides a low noise regulated output as well as lower input noise than conventional switch capacitor charge pump regulators.
PAGE 10
LTC3245 Applications Information Short-Circuit/Thermal Protection The LTC3245 has built-in short-circuit current limiting as well as overtemperature protection. During short-circuit conditions the device will automatically limit the output current. The LTC3245 has thermal protection that will shut down the device if the junction temperature exceeds the overtemperature threshold (typically 175°C).
PAGE 11
LTC3245 Applications Information 2:1 Step-Down Charge Pump Operation 1:2 Step-Up Charge Pump Operation When the input supply is greater than about two times the output voltage, the LTC3245 will operate in 2:1 stepdown mode. Charge transfer happens in two phases. On the first phase the flying capacitor (CFLY ) is connected between VIN and VOUT. On this phase CFLY is charged up and current is delivered to VOUT. On the second phase the flying capacitor (CFLY ) is connected between VOUT and GND.
PAGE 12
LTC3245 Applications Information strength. The value of COUT directly controls the amount of output ripple for a given load current when operating in constant frequency mode. Increasing the size of COUT will reduce the output ripple. To reduce output noise and ripple, it is suggested that a low ESR (equivalent series resistance < 0.1Ω) ceramic capacitor (10μF or greater) be used for COUT.
PAGE 13
LTC3245 Applications Information rather than discussing the specified capacitance value. For example, over rated voltage and temperature conditions, a 4.7μF, 10V, Y5V ceramic capacitor in an 0805 case may not provide any more capacitance than a 1μF, 10V, X5R or X7R available in the same 0805 case. In fact, over bias and temperature range, the 1μF, 10V, X5R or X7R will provide more capacitance than the 4.7μF, 10V, Y5V.
PAGE 14
LTC3245 Typical Applications Regulated 5V Low Noise Output 1µF C+ C– LTC3245 VIN + 12V LEAD ACID BATTERY 1µF VOUT BURST OUTS/ADJ SEL2 PGOOD SEL1 GND 100k VOUT = 5V IVOUT UP TO 250mA 10µF 3245 TA02 High Efficiency 3.3V Microcontroller Supply from 9V Alkaline (with Power-On Reset Delay) 1µF C+ C– LTC3245 VIN + 9V ALKALINE BATTERY 1µF VOUT SEL1 OUTS/ADJ SEL2 PGOOD VOUT = 3.3V 510k MICROCONTROLLER VDD 10µF POR 1µF BURST GND GND 3245 TA03 Wide Input Range Low Noise 3.
PAGE 15
LTC3245 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 12-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1666 Rev G) BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ±0.102 (.112 ±.004) 5.10 (.201) MIN 2.845 ±0.102 (.112 ±.004) 0.889 ±0.127 (.035 ±.005) 6 1 1.651 ±0.102 (.065 ±.004) 1.651 ±0.102 3.20 – 3.45 (.065 ±.004) (.126 – .136) 12 0.65 0.42 ±0.038 (.0256) (.0165 ±.
PAGE 16
LTC3245 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DE/UE Package 12-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695 Rev D) 0.70 ±0.05 3.60 ±0.05 2.20 ±0.05 3.30 ±0.05 1.70 ± 0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.50 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ±0.10 (2 SIDES) 7 R = 0.115 TYP 0.40 ± 0.10 12 R = 0.05 TYP PIN 1 TOP MARK (NOTE 6) 0.
PAGE 17
LTC3245 Revision History REV DATE DESCRIPTION A 7/13 Added MP-grade in MSOP package to Order Information table PAGE NUMBER 2 Modified Note 2 to add MP-grade 3 3245fa 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 information circuits as described herein will not infringe on existing patent rights. For more www.
PAGE 18
LTC3245 Typical Application Wide VIN 5V Supply with Battery Backup 1µF C+ 12V TO 24V C– LTC3245 VIN + + + 1µF 4 × AA SEL2 BURST VOUT OUTS/ADJ PGOOD VOUT = 5V IVOUT UP TO 250mA 10µF SEL1 + GND 3245 TA05 Related Parts PART NUMBER DESCRIPTION COMMENTS LTC1751-3.3/ LTC1751-5 100mA, 800kHz Regulated Doubler VIN: 2V to 5V, VOUT(MAX) = 3.3V/5V, IQ = 20μA, ISD < 2μA, MS8 Package LTC1983-3/ LTC1983-5 100mA, 900kHz Regulated Inverter VIN: 3.3V to 5.