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LTC3026

3026ff

Typical applicaTion

FeaTures

applicaTions

DescripTion

1.5A Low Input Voltage

VLDO Linear Regulator

The LTC

3026 is a very low dropout (VLDO™) linear regula-

tor that can operate at input voltages down to 1.14V. The

device is capable of supplying 1.5A of output current with

a typical dropout voltage of only 100mV. To allow opera-

tion at low input voltages the LTC3026 includes a boost

converter that provides the necessary headroom for the

internal LDO circuitry.

Output current comes directly from the input supply to

maximize efficiency. The boost converter requires only a

small chip inductor and ceramic capacitor for operation.

Additionally, the boosted output voltage of one LTC3026

can supply the boost voltage for other LTC3026s, thus

requiring a single inductor for multiple LDOs. A user sup-

plied boost voltage can be used eliminating the need for

an inductor altogether.

The LTC3026 regulator is stable with 10µF or greater

ceramic output capacitors. The device has a low 0.4V

reference voltage which is used to program the output

voltage via two external resistors. The device also has

internal current limit, overtemperature shutdown, and

reverse output current protection. The LTC3026 is avail-

able in a small 10-lead MSOP or low profile (0.75mm)

10-lead 3mm × 3mm DFN package.

1.2V Output Voltage from 1.5V Input Supply

Input Voltage Range:

1.14V to 3.5V (with Boost Enabled)

1.14V to 5.5V (with External 5V Boost)

Low Dropout Voltage: 100mV at I

OUT

= 1.5A

Adjustable Output Range: 0.4V to 2.6V

Output Current: Up to 1.5A

Excellent Supply Rejection Even Near Dropout

Shutdown Disconnects Load from V

and V

BST

Low Operating Current: I

= 950µA at V

= 1.5V

Low Shutdown Current:

< 1µA (Typ), I

BST

= 0.1µA (Typ)

Stable with 10µF or Greater Ceramic Capacitors

Short-Circuit, Reverse Current Protected

Overtemperature Protected

Available in 10-Lead MSOP and 10-Lead

(3mm × 3mm) DFN Packages

High Efficiency Linear Regulator

Post Regulator for Switching Supplies

Microprocessor Supply

Dropout Voltage vs Output Current

0.4V

OUT

BST

5V BOOST

CONVERTER

GND

ADJ

10µH

4.7µF

OUT

10µF

= 1.5V

OUT

= 1.2V,

1.5A

OFF ON

100k

8.06k

4.02k

LTC3026

3026 TA01a

SHDN

L1: MURATA LQH2MCN100K02

–

4.7µF

OUT

(A)

DROPOUT (mV)

100

150

3026 TA01b

0.5

1.0

1.5

1.2V

1.5V

2.0V

2.6V

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

and ThinSOT, VLDO are trademarks of Linear Technology Corporation. All other trademarks are

the property of their respective owners.

Downloaded from Arrow.com.

Summary of content (18 pages)

PAGE 1
LTC3026 1.5A Low Input Voltage VLDO Linear Regulator Features n n n n n n n n n n n n Description Input Voltage Range: 1.14V to 3.5V (with Boost Enabled) 1.14V to 5.5V (with External 5V Boost) Low Dropout Voltage: 100mV at IOUT = 1.5A Adjustable Output Range: 0.4V to 2.6V Output Current: Up to 1.5A Excellent Supply Rejection Even Near Dropout Shutdown Disconnects Load from VIN and VBST Low Operating Current: IIN = 950µA at VIN = 1.5V Low Shutdown Current: IIN < 1µA (Typ), IBST = 0.
PAGE 2
LTC3026 Absolute Maximum Ratings (Note 1) VBST to GND.................................................. –0.3V to 6V VIN to GND.................................................... –0.3V to 6V PG to GND.................................................... –0.3V to 6V SHDN to GND............................................. –0.3V to 6.3V ADJ to GND................................... –0.3V to (VIN + 0.3V) Output Short-Circuit Duration...........................
PAGE 3
LTC3026 Electrical Characteristics (BOOST ENABLED, LSW = 10µH) The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TJ = 25°C. VIN = 1.5V, VOUT = 1.2V, CIN = CBST = 4.7µF, COUT = 10µF (all capacitors ceramic) unless otherwise noted. SYMBOL PARAMETER CONDITIONS VIN Operating Voltage (Note 2) IIN Operating Current IOUT = 0mA, VOUT = 0.8V, VSHDN = VIN, VIN = 1.2V IOUT = 0mA, VOUT = 1.2V, VSHDN = VIN, VIN = 1.
PAGE 4
LTC3026 electrical characteristics (BOOST ENABLED or DISABLED) The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TJ = 25°C. VIN = 1.5V, VOUT = 1.2V, CIN = CBST = 1µF, COUT = 10µF (all capacitors ceramic) unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VIHSHDN SHDN Input High Voltage 1.14V ≤ VIN ≤ 3.5V 3.5V ≤ VIN ≤ 5.5V l l 1.0 1.2 VILSHDN SHDN Input Low Voltage 1.14V ≤ VIN ≤ 5.5V l 0.
PAGE 5
LTC3026 Typical Performance Characteristics ADJ Voltage vs Temperature IN Shutdown Current 4.5 403 4.0 1mA 400 1.5A 399 398 397 –25 0 25 50 100 75 TEMPERATURE (°C) 2.5 2.0 125 160 50 RIPPLE REJECTION (dB) 120 100 80 60 –40°C 25°C 85°C 125°C 40 20 1.8 2.0 2.4 2.2 VIN (V) 4.950 –50 20 VBST = 5V VOUT =1.2V IOUT = 800mA COUT = 10µF 1.4 1.6 1.8 2.
PAGE 6
LTC3026 Typical Performance Characteristics Delay from Enable to PG with Boost Disabled Delay from Enable to PG with Boost Enabled 5.0 400 VOUT = 0.8V ROUT = 8Ω –40°C 25°C 85°C 4.5 375 4.0 3.5 DELAY (ms) DELAY (µs) 350 325 300 250 2mA OUT AC 20mV/DIV 3.0 2.5 2.0 1.0 0.5 0 1.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN (V) 1.5 3026 G13 IN Supply Transient Response 2.5 2.0 VIN (V) 3.0 3.5 VOUT = 1.5V COUT = 10µF VIN = 1.
PAGE 7
LTC3026 Pin Functions IN (Pins 1, 2): Input Supply Voltage. Output load current is supplied directly from IN. The IN pin should be locally bypassed to ground if the LTC3026 is more than a few inches away from another source of bulk capacitance. In general, the output impedance of a battery rises with frequency, so it is usually advisable to include an input bypass capacitor when supplying IN from a battery. A capacitor in the range of 0.1µF to 4.7µF is usually sufficient.
PAGE 8
LTC3026 Block Diagram 4 SHDN 6 BOOST CONVERTER 5 BST SWITCHING LOGIC – SW EN + SHDN – UVLO 7 – – PG IN 1,2 + 0.4V REFERENCE 0.372V VOFF OUT 9,10 + – + + 8 ADJ OVERSHOOT DETECT GND 3,11 3026 BD 3026ff 8 Downloaded from Arrow.com.
PAGE 9
LTC3026 Operation The LTC3026 is a VLDO (very low dropout) linear regulator which operates from input voltages as low as 1.14V. The LDO uses an internal NMOS transistor as the pass device in a source-follower configuration. The BST pin provides the higher supply necessary for the LDO circuitry while the output current comes directly from the IN input for high efficiency regulation.
PAGE 10
LTC3026 operation The LDO provides a high accuracy output capable of supplying 1.5A of output current with a typical dropout voltage of only 100mV. A single ceramic capacitor as small as 10µF is all that is required for output bypassing. A low reference voltage allows the LTC3026 output to be programmed to much lower voltages than available in common LDOs (range of 0.4V to 2.6V). The devices also include current limit and thermal overload protection, and will survive an output short-circuit indefinitely.
PAGE 11
LTC3026 Operation The LTC3026 operates at a relatively high gain of 270µV/A referred to the ADJ input. Thus, a load current change of 1mA to 1.5A produces a 400µV drop at the ADJ input. To calculate the change in the output, simply multiply by the gain of the feedback network (i.e. 1 + R2/R1). For example, to program the output for 1.2V choose R2/R1 = 2. In this example an output current change of 1mA to 1.5A produces –400µV • (1 + 2) = 1.2mV drop at the output.
PAGE 12
LTC3026 operation Boost Converter Component Selection A 10µH chip inductor with a peak saturation current (ISAT) of at least 150mA is recommended for use with the internal boost converter. The inductor value can range between 4.7µH to 40µH, but values less than 10µH result in higher switching frequency, increased switching losses, and lower max output current available at the BST pin. See Table 1 for a list of component suppliers. Table 1.
PAGE 13
LTC3026 Operation temperatures, or in cases where internal power dissipation cause excessive self heating on-chip, the thermal shutdown circuitry will shut down the boost converter and LDO when the junction temperature exceeds approximately 150°C. It will reenable the converter and LDO once the junction temperature drops back to approximately 140°C. The LTC3026 will cycle in and out of thermal shutdown without latchup or damage until the overstress condition is removed.
PAGE 14
LTC3026 Typical Applications Using 1 Boost with Multiple Regulators VIN = 2.5V TO ADDITIONAL REGULATORS 10µH BST SW NC IN 1µF LTC3026 VOUT1 1.8V, 1.5A OUT BST SW 4.7µF LTC3026 VOUT2 1.5V, 1.5A OUT IN 11k 14k SHDN COUT1 10µF ADJ 100k 4.7µF GND 4.02k 100k 1µF PG1 PG COUT2 10µF ADJ SHDN GND PG 4.02k PG2 BOOT STRAPPED LTC3026 (BOOST DISABLED) LTC3026 WITH BOOST ENABLED FANOUT: 3-LTC3026 FOR VIN <1.4V 5-LTC3026 FOR VIN >1.4V 3026 TA02 2.5V Output from 3.
PAGE 15
LTC3026 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 10-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1664 Rev H) BOTTOM VIEW OF EXPOSED PAD OPTION 1.88 ±0.102 (.074 ±.004) 5.23 (.206) MIN 1 0.889 ±0.127 (.035 ±.005) 1.68 ±0.102 (.066 ±.004) 0.05 REF 10 0.305 ± 0.038 (.0120 ±.0015) TYP RECOMMENDED SOLDER PAD LAYOUT 3.00 ±0.102 (.118 ±.
PAGE 16
LTC3026 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699 Rev C) 0.70 ±0.05 3.55 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.10 (4 SIDES) R = 0.125 TYP 6 0.40 ±0.10 10 1.65 ±0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.
PAGE 17
LTC3026 Revision History (Revision history begins at Rev D) REV DATE DESCRIPTION PAGE NUMBER D 3/10 Addition to Absolute Maximum Ratings Changes to Electrical Characteristics 5/11 F 8/12 3, 4 Changes to Pin Functions 7, Changes to Operation Section 9 Changes to Typical Applications E 1 14, 18 Additions to Related Parts 18 Remove I-grade in Note 8.
PAGE 18
LTC3026 Typical Application Efficient, Low Noise 1.5V Output from 1.8V DC/DC Buck Converter (LTC3026 Boost Converter Disabled) 4.5V ≤ VIN ≤ 5.5V 33pF 200pF 30k 1 ITH 0.1µF 10 SW RSENSE 0.04Ω LTC1773 2 3 4 CIN 47µF 10V 5 RUN/SS 9 SENSE– SYNC/FCB 8 VIN VFB TG GND BG L1 2.5µH 7 VBUCK 1.8V N/C 2A SW BST LTC3026 IN OUT SHDN ADJ 11k 6 1µF Si9942DY 80.6k 1% 1µF CBUCK 47µF 10V 100k 1% 100k GND 4.02k VOUT 1.5V 1.