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LTC3025

3025fd

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

300mA Micropower

VLDO Linear Regulator

The LTC

3025 is a micropower, VLDO

(very low drop-

out) linear regulator which operates from input voltages as

low as 0.9V. The device is capable of supplying 300mA of

output current with a typical dropout voltage of only 45mV.

A BIAS supply is required to run the internal reference and

LDO circuitry while output current comes directly from

the IN supply for high efﬁ ciency regulation. The low 0.4V

internal reference voltage allows the LTC3025 output to

be programmed to much lower voltages than available in

common LDOs (range of 0.4V to 3.6V). The output voltage

is programmed via two ultrasmall SMD resistors.

The LTC3025’s low quiescent current makes it an ideal

choice for use in battery-powered systems. For 3-cell

NiMH and single cell Li-Ion applications, the BIAS voltage

can be supplied directly from the battery while the input

can come from a high efﬁ ciency buck regulator, providing

a high efﬁ ciency, low noise output.

Other features include high output voltage accuracy,

excellent transient response, stability with ultralow ESR

ceramic capacitors as small as 1µF, short-circuit and

thermal overload protection and output current limiting.

The LTC3025 is available in a tiny, low proﬁ le (0.75mm)

6-lead DFN (2mm × 2mm) package.

1.2V Output Voltage from 1.5V Input Supply

Wide Input Voltage Range: 0.9V to 5.5V

Stable with Ceramic Capacitors

Very Low Dropout: 45mV at 300mA

Adjustable Output Range: 0.4V to 3.6V

±2% Voltage Accuracy over Temperature

Supply Load

Low Noise: 80µV

RMS

(10Hz to 100kHz)

BIAS Voltage Range: 2.5V to 5.5V

Fast Transient Recovery

Shutdown Disconnects Load from V

and V

BIAS

Low Operating Current: I

= 4µA, I

BIAS

= 50µA Typ

Low Shutdown Current: I

= 1µA, I

BIAS

= 0.01µA Typ

Output Current Limit

Thermal Overload Protection

Available in 6-Lead (2mm × 2mm) DFN Package

Low Power Handheld Devices

Low Voltage Logic Supplies

DSP Power Supplies

Cellular Phones

Portable Electronic Equipment

Handheld Medical Instruments

Post Regulator for Switching Supply Noise Rejection

1MHz V

Supply Rejection

LTC3025

BIAS

0.1µF

1.5V

1µF

0.1µF

Li-Ion

3-CELL

NiMH

SHDN

OUT

80.6k

OUT

= 1.2V

OUT

≤ 300mA

40.2k

3025 TA01

ADJ

GNDOFF ON

1.5V HIGH

EFFICIENCY

DC/DC

BUCK

(V)

1.2

REJECTION (dB)

1.6

2.0

2.2

3025 TA01b

1.4

1.8

2.4

2.6

BIAS = 3.6V

OUT

= 1.2V

OUT

= 100mA

OUT

= 300mA

OUT

= 1µF

OUT

= 10µF

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

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

property of their respective owners.

Summary of content (12 pages)

PAGE 1
LTC3025 300mA Micropower VLDO Linear Regulator FEATURES DESCRIPTION n The LTC®3025 is a micropower, VLDOTM (very low dropout) linear regulator which operates from input voltages as low as 0.9V. The device is capable of supplying 300mA of output current with a typical dropout voltage of only 45mV. A BIAS supply is required to run the internal reference and LDO circuitry while output current comes directly from the IN supply for high efﬁciency regulation. The low 0.
PAGE 2
LTC3025 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Notes 1, 2) TOP VIEW VBIAS, VIN to GND......................................... –0.3V to 6V SHDN to GND............................................... –0.3V to 6V ADJ to GND.................................................. –0.3V to 6V VOUT ........................................–0.3V to VIN + 0.3V or 6V Operating Junction Temperature Range (Note 3).................................................. –40°C to 125°C Storage Temperature Range..............
PAGE 3
LTC3025 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 1.5V, VBIAS = 3.6V, VOUT = 1.2V, COUT = 1μF, CIN = 0.1μF, CBIAS = 0.1μF (all capacitors ceramic) unless otherwise noted. (Note 3) PARAMETER CONDITIONS MIN VIN to VOUT Dropout Voltage (Notes 4, 6, 7) VBIAS = 2.8V, VIN = 1.5V, VADJ = 0.37V, IOUT = 300mA TYP MAX UNITS 45 100 mV 1.
PAGE 4
LTC3025 TYPICAL PERFORMANCE CHARACTERISTICS VIN No Load Operating Current VBIAS = 5V VOUT = 0.8V VBIAS = 5V 8 85°C 6 403 5 125°C 25°C –40°C 4 3 25°C –40°C 4 2 2 1 401 400 399 398 397 0 0.5 0 0.5 2.5 3.5 5.5 4.5 396 1.5 2.5 VIN (V) 3.5 50 25 0 75 TEMPERATURE (°C) –25 VIN (V) 125 Burst Mode DC/DC Buck Ripple Rejection Current Limit vs VIN Voltage 1000 100 3025 G06 3025 G05 SHDN Threshold vs Temperature 1600 VBIAS = 3.
PAGE 5
LTC3025 TYPICAL PERFORMANCE CHARACTERISTICS 3MHz VIN Supply Rejection Transient Response 50 250mA REJECTION (dB) 45 40 COUT = 10μF 35 COUT = 1μF IOUT 10mA 30 25 VOUT AC 10mV/DIV 20 15 10 5 VBIAS = 3.6V VOUT = 1.2V 0 1.2 1.4 1.6 IOUT = 100mA IOUT = 300mA 1.8 2.0 VIN (V) 2.2 2.4 2.6 VIN = 1.5V VOUT = 1.2V VBIAS = 3.6V COUT = 1μF 100μs/DIV 3025 G13 3025 G12 PIN FUNCTIONS BIAS (Pin 1): BIAS Input Voltage. BIAS provides internal power for LTC3025 circuitry.
PAGE 6
LTC3025 BLOCK DIAGRAM 1 BIAS REFERENCE 6 SHDN SHDN SOFT-START 0.4V IN + – 2 3 6μA OUT GND ADJ 4 5 3025 BD APPLICATIONS INFORMATION Operation (Refer to Block Diagram) The LTC3025 is a micropower, VLDO (very low dropout) linear regulator which operates from input voltages as low as 0.9V. The device provides a high accuracy output that is capable of supplying 300mA of output current with a typical dropout voltage of only 45mV.
PAGE 7
LTC3025 APPLICATIONS INFORMATION The LTC3025 operates at a relatively high gain of –0.7μV/ mA referred to the ADJ input. Thus a load current change of 1mA to 300mA produces a –0.2mV drop at the ADJ input. To calculate the change referred to 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 300mA produces –0.2mV • (1 + 2) = 0.6mV drop at the output.
PAGE 8
LTC3025 APPLICATIONS INFORMATION temperature range. The X5R and X7R dielectrics result in more stable characteristics and are usually more suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available in higher values. In all cases, the output capacitance should never drop below 0.4μF, or instability or degraded performance may occur.
PAGE 9
LTC3025 APPLICATIONS INFORMATION The LTC3025 will cycle in and out of thermal shutdown without latch-up or damage until the overstress condition is removed. Long term overstress (TJ > 125°C) should be avoided as it can degrade the performance or shorten the life of the part. Soft-Start Operation The LTC3025 includes a soft-start feature to prevent excessive current ﬂow during start-up. When the LDO is enabled, the soft-start circuitry gradually increases the LDO reference voltage from 0V to 0.
PAGE 10
LTC3025 PACKAGE DESCRIPTION DC Package 6-Lead Plastic DFN (2mm × 2mm) (Reference LTC DWG # 05-08-1703 Rev B) 0.70 p0.05 2.55 p0.05 1.15 p0.05 0.61 p0.05 (2 SIDES) PACKAGE OUTLINE 0.25 p 0.05 0.50 BSC 1.42 p0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.125 TYP 0.56 p 0.05 (2 SIDES) 0.40 p 0.10 4 6 2.00 p0.10 (4 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) PIN 1 NOTCH R = 0.20 OR 0.25 s 45o CHAMFER R = 0.05 TYP 0.200 REF 0.75 p0.05 (DC6) DFN REV B 1309 3 1 0.25 p 0.05 0.50 BSC 1.
PAGE 11
LTC3025 REVISION HISTORY REV DATE C 07/10 (Revision history begins at Rev C) DESCRIPTION PAGE NUMBER Added (Note 3) notation to “The l denotes” statement in Electrical Characteristics section Updated Pin 7 in Pin Functions D 01/11 2, 3 6 Added “VOUT Start-Up and Supply Sequencing” section 9 Updated Related Parts section 12 Updated graph G11 4 3025fd Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
PAGE 12
LTC3025 TYPICAL APPLICATION High Efﬁciency 1.5V Step-Down Converter with Efﬁcient 1.2V VLDO Output OFF ON 1 0.1μF VIN 2.7V TO 5.5V 4 CIN** 4.7μF CER VIN SW 3 LTC3406-1.5 1 RUN VOUT 5 2.2μH* VOUT 1.5V 600mA OUT BIAS 80.6k LTC3025 3 IN ADJ 1μF VOUT = 1.2V IOUT ≤ 300mA 5 40.2k OFF ON 6 SHDN GND 2 3025 TA02 + COUT 10μF CER GND 4 *MURATA LQH32CN2R2M33 **TAIYO YUDEN JMK212BJ475MG † TAIYO YUDEN JMK316BJ106ML Efﬁciency vs Output Current 100 EFFICIENCY (%) 90 VOUT = 1.