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LTC3459

3459fc

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

10V Micropower

Synchronous Boost Converter

The LTC

3459 is a low current, high efﬁ ciency synchronous

boost converter intended for low power, size constrained

portable applications. The LTC3459 can be powered from

a single lithium ion battery, a 2- to 3-cell stack of alkaline

or nickel batteries, or any low impedance voltage source

between 1.5V and 5.5V. The output is programmable via

an external divider between 2.5V and 10V. Although the

part is primarily intended for boost applications, V

OUT

will

maintain regulation below V

(at reduced efﬁ ciency).

The LTC3459 offers Burst Mode operation with a ﬁ xed

peak current, providing high conversion efﬁ ciency over

a wide range of load currents. During start-up, inductor

current is controlled preventing the inrush surge current

found in many boost converters. In shutdown the output

is disconnected from the input and quiescent current is

reduced to <1μA.

The LTC3459 is offered in low proﬁ le 6-pin 2mm × 2mm

DFN, 2mm × 3mm DFN or SOT-23 (ThinSOT

) packages,

allowing a tiny footprint for the total solution.

5V to 8V Converter

Small Solution Size

>85% Efﬁ ciency over Wide Load Range

Internal Synchronous Rectiﬁ er

Range: 1.5V to 5.5V

5V at 30mA from 3.3V Input

3.3V at 20mA from 2 AA Cell Input

Programmable Output Voltages Up to 10V

Burst Mode

Operation

Inrush Current Limiting

Output Disconnect in Shutdown

Ultralow Quiescent (10μA) and Shutdown (<1μA)

Currents

Low Proﬁ le 2mm × 2mm DFN, 2mm × 3mm DFN or

SOT-23 Package

General Purpose Micropower Boost

Digital Cameras

PDAs

LCD Bias

Small OLED Displays

Supercap Charging

, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology

Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners.

Efﬁ ciency

μH

2M 47pF

OUT

30mA

4.7

μF

1μF

LTC3459

SHDN

OUT

FBOFF ON

GND

365k

3459 TA01a

LOAD

(mA)

EFFICIENCY (%)

100

0.01 1 10 100

3459 TA01b

0.1

= 5V

OUT

= 8V

Summary of content (12 pages)

PAGE 1
LTC3459 10V Micropower Synchronous Boost Converter FEATURES DESCRIPTION n The LTC®3459 is a low current, high efﬁciency synchronous boost converter intended for low power, size constrained portable applications. The LTC3459 can be powered from a single lithium ion battery, a 2- to 3-cell stack of alkaline or nickel batteries, or any low impedance voltage source between 1.5V and 5.5V. The output is programmable via an external divider between 2.5V and 10V.
PAGE 2
LTC3459 ABSOLUTE MAXIMUM RATINGS Referred to GND (Note 1) VIN, FB Voltage ........................................... –0.3V to 7V VOUT, SHDN Voltage ................................. –0.3V to 10V SW Voltage .............................................. –0.3V to 12V Operating Temperature Range (Notes 2, 3) ......................................... –40°C to 85°C Storage Temperature Range.................. –65°C to 150°C Reﬂow Temperature ..............................................
PAGE 3
LTC3459 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 3.3V, VOUT = 5V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS VIN l Input Voltage Range 1.5 5.5 V VIN Quiescent Current SHDN = VCC 10 20 μA VIN Shutdown Current SHDN = GND 0.1 1 μA VOUT l Programmable Voltage Range 10 V VOUT Quiescent Supply Current SHDN = VCC 2.
PAGE 4
LTC3459 TYPICAL PERFORMANCE CHARACTERISTICS Minimum ROUT vs VIN 2500 2000 1500 VIN = 3.3V 14 VOUT = 5V VOUT = 10V VOUT = 7.5V VOUT = 5V VOUT = 3.3V L = 22μH 350 300 POUT (mW) ROUT (Ω) 3000 16 400 VOUT = 10V VOUT = 7.5V VOUT = 5V VOUT = 3.3V L = 22μH 3500 VIN and VOUT Quiescent Current vs Temperature Maximum POUT vs VIN 12 CURRENT (μA) 4000 (TA = 25°C, unless otherwise noted). 250 200 150 IIN 10 8 6 1000 100 4 500 50 2 0 1.5 2 2.5 3.5 3 4 4.5 5 0 1.5 5.5 2 2.
PAGE 5
LTC3459 TYPICAL PERFORMANCE CHARACTERISTICS VOUT AC Ripple Burst Cycle VOUT 50mV/DIV INDUCTOR CURRENT 50mA/DIV VIN = 3.3V VOUT = 5V L = 22μH COUT = 4.7μF CFF = 47pF (TA = 25°C, unless otherwise noted).
PAGE 6
LTC3459 PIN FUNCTIONS (DC/DCB/S6 Packages) GND (Pin 5/Pin 5/Pin 2): Signal and Power Ground. Provide a short, direct PCB path between GND and the (–) side of the ﬁlter capacitors on VIN and VOUT. VIN (Pin 1/Pin 6/Pin 6): Input Supply Pin. Bypass VIN with a low ESR, ESL ceramic capacitor of at least 1μF. VOUT (Pin 2/Pin 2/Pin 5): Regulated Output Voltage of the Boost Regulator. Bypass VOUT with a low ESR, ESL ceramic capacitor between 2.2μF and 10μF. VOUT ripple increases with smaller capacitors.
PAGE 7
LTC3459 OPERATION Operation The LTC3459 synchronous boost converter utilizes a Burst Mode control technique to achieve high efﬁciency over a wide dynamic range. A 2.5% accurate comparator is used to monitor the output voltage (VOUT), if VOUT is above the comparator threshold, no switching occurs and only quiescent current (10μA) is drawn from the power source. When VOUT drops below the comparator threshold, switching commences and the output capacitor is charged.
PAGE 8
LTC3459 OPERATION This is accomplished by varying the tOFF period by approximately 1/(VOUT – VIN). Due to propagation delays and a 0.6μA bias current in the timer, the tOFF time can be more accurately predicted as follows: tOFF ≈ 100ns + 0.8 pF • 1.25V V –V 0.6μA + OUT IN 500k If VOUT is less than VIN, the tOFF delay is ﬁxed at approximately 750ns. APPLICATIONS INFORMATION Inductor Selection Capacitor Selection An inductor with a minimum value of 15μH is recommended for use with the LTC3459.
PAGE 9
LTC3459 TYPICAL APPLICATIONS Very low operating quiescent current and synchronous operation allow for greater than 85% conversion efﬁciency in many applications. Lower output voltages will result in lower efﬁciencies since the N- and P-channel RDS(ON)s will increase. The switching frequency and output power capability of the LTC3459 are also dependant on input and output voltages. The LTC3459 is designed to control peak inductor current when VIN is greater than or less than VOUT.
PAGE 10
LTC3459 TYPICAL APPLICATIONS controlled, preventing any damaging effects of inrush current. Proper heat sinking of the package is required in this application as the die may dissipate 100mW to 200mW during initial charging. When VOUT is greater than ~3.5V, normal boost mode operation and efﬁciency begin, with the P-channel MOSFET acting as a synchronous switch. Average input current is a constant 50mA during charging, where the current delivered to the SuperCap varies somewhat with duty cycle.
PAGE 11
LTC3459 PACKAGE DESCRIPTION DCB Package 6-Lead Plastic DFN (2mm × 3mm) (Reference LTC DWG # 05-08-1715) R = 0.115 TYP R = 0.05 TYP 2.00 ±0.10 (2 SIDES) 0.70 ±0.05 3.55 ±0.05 PACKAGE OUTLINE 1.65 ±0.05 (2 SIDES) 3.00 ±0.10 (2 SIDES) 0.40 ± 0.10 4 6 1.65 ± 0.10 (2 SIDES) 2.15 ±0.05 PIN 1 NOTCH R0.20 OR 0.25 × 45° CHAMFER PIN 1 BAR TOP MARK (SEE NOTE 6) 3 0.25 ± 0.05 0.50 BSC 1.35 ±0.05 (2 SIDES) 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 0.200 REF (DCB6) DFN 0405 1 1.35 ±0.
PAGE 12
LTC3459 TYPICAL APPLICATION 3.3V from a 2 AA Alkaline Input L1 15μH SW + C1 2.2μF + OFF ON VOUT VIN R1 604k LTC3459 SHDN C2 47pF C3 4.7μF FB R2 365k GND VOUT = 3.3V 90 VOUT 3.3V VIN = 3V EFFICIENCY (%) VIN 1.8V TO 3V 2 AA CELLS 100 80 VIN = 1.8V 70 3459 TA06a 60 C1: TDK C1608X5R1A225MT C2: TDK C0603COG1E470J C3: TDK C2012X5ROJ475K L1: COILCRAFT DO3314-153MXB R1: PANASONIC ERJ3EKF6043V R2: PANASONIC ERJ3EKF3653V 50 0.01 0.