Datasheet

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LT3028

3028f

Dual 100mA/500mA

Low Dropout, Low Noise,

Micropower Regulators with

Independent Inputs

■

Low Noise: 20µV

RMS

(10Hz to 100kHz)

■

Low Quiescent Current: 30µA/Output

■

Independent Inputs

■

Wide Input Voltage Range: 1.8V to 20V

■

Output Current: 100mA/500mA

■

Very Low Shutdown Current: <0.1

■

Low Dropout Voltage: 300mV/320mV at

100mA/500mA

■

Adjustable Outputs from 1.22V to 20V

■

Stable with as Low as 1µF/3.3µF Output Capacitor

■

Stable with Aluminum, Tantalum or

Ceramic Capacitors

■

Reverse-Battery Protected

■

No Protection Diodes Needed

■

Overcurrent and Overtemperature Protected

■

Tracking/Sequencing Capability

■

Thermally Enhanced 16-Lead TSSOP and 16-Lead

(5mm × 3mm) DFN Packages

The LT

3028 is a dual, micropower, low noise, low drop-

out regulator with independent inputs. With an external

0.01µF bypass capacitor, output noise is a low 20µV

RMS

over a 10Hz to 100kHz bandwidth. Designed for use in

battery-powered systems, the low 30µA quiescent current

per output makes it an ideal choice. In shutdown, quies-

cent current drops to less than 0.1µA. Shutdown control

is independent for each output, allowing for flexibility in

power management. The device is capable of operating

over an input voltage range of 1.8V to 20V. Output 1 can

supply 500mA of output current with a dropout voltage of

320mV. The device can supply 100mA of output current

from Output 2 with a dropout voltage of 300mV. Quiescent

current is well controlled in dropout.

The LT3028 regulator is stable with output capacitors as

low as 1µF for the 100mA output and 3.3µF for the 500mA

output. Small ceramic capacitors can be used without the

series resistance required by other regulators.

Internal protection circuitry includes reverse-battery pro-

tection, current limiting and thermal limiting protection.

The device is available as an adjustable device with a 1.22V

reference voltage. The LT3028 regulator is available in the

thermally enhanced 16-lead TSSOP and 16-lead, low

profile (5mm × 3mm × 0.75mm) DFN packages.

10Hz to 100kHz Output Noise

3.3V/2.5V Low Noise Regulators

■

Cellular Phones

■

Pagers

■

Battery-Powered Systems

■

Frequency Synthesizers

■

Wireless Modems

■

Tracking/Sequencing Power Supplies

, LTC and LT are registered trademarks of Linear Technology Corporation.

OUT

100µV/DIV

20µV

RMS

3028 TA01b

3.3V AT 500mA

20µV

RMS

NOISE

249k

0.01µF 10µF

422k

3028 TA01a

OUT2

2.5V AT 100mA

20µV

RMS

NOISE

ADJ2

BYP2

GND

249k

0.01µF 10µF

261k

OUT1

ADJ1

BYP1

LT3028

IN1

3.7V TO

20V

1µF

SHDN1

IN2

2.9V TO

20V

1µF

SHDN2

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

Protected by U.S. Patents including 6118263, 6144250.

Summary of content (16 pages)

PAGE 1
LT3028 Dual 100mA/500mA Low Dropout, Low Noise, Micropower Regulators with Independent Inputs U FEATURES DESCRIPTIO ■ The LT ®3028 is a dual, micropower, low noise, low dropout regulator with independent inputs. With an external 0.01µF bypass capacitor, output noise is a low 20µVRMS over a 10Hz to 100kHz bandwidth. Designed for use in battery-powered systems, the low 30µA quiescent current per output makes it an ideal choice. In shutdown, quiescent current drops to less than 0.1µA.
PAGE 2
LT3028 W W W AXI U U ABSOLUTE RATI GS (Note 1) IN1, IN2 Pin Voltage .............................................. ±20V OUT1, OUT2 Pin Voltage ....................................... ±20V Input-to-Output Differential Voltage ....................... ±20V ADJ1, ADJ2 Pin Voltage ......................................... ±7V BYP1, BYP2 Pin Voltage ....................................... ±0.6V SHDN1, SHDN2 Pin Voltage ................................. ±20V Output Short-Circut Duration ....................
PAGE 3
LT3028 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
PAGE 4
LT3028 ELECTRICAL CHARACTERISTICS Note 4: Operating conditions are limited by maximum junction temperature. The regulated output voltage specification will not apply for all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range must be limited. When operating at maximum output current, the input voltage range must be limited.
PAGE 5
LT3028 U W TYPICAL PERFOR A CE CHARACTERISTICS ADJ1 or ADJ2 Pin Voltage 45 1.235 40 35 VSHDN = VIN 30 25 20 15 TJ = 25°C 35 RL = 250k IL = 1mA 1.230 1.225 1.220 1.215 1.210 10 5 VIN = 6V RL = 250k, IL = 5µA 0 0 25 –50 –25 50 75 100 125 25 50 75 RL = 24.4Ω IL = 50mA* 0.75 0.25 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 1000 2.00 1.75 1.50 1.25 1.00 0.75 10 0 12 TJ = 25°C VIN = VSHDN *FOR VOUT = 1.22V 400 RL = 122Ω IL = 10mA* 200 RL = 1.22k IL = 1mA* 4 RL = 12.
PAGE 6
LT3028 U W TYPICAL PERFOR A CE CHARACTERISTICS SHDN1 or SHDN2 Pin Input Current 1.0 0.9 0.9 IL = FULL 0.8 0.7 0.6 IL = 1mA 0.5 0.4 0.3 0.2 0.1 SHDN1 or SHDN2 Pin Input Current 1.4 TJ = 25°C SHDN PIN INPUT CURRENT (µA) 1.0 SHDN PIN INPUT CURRENT (µA) SHDN PIN THRESHOLD (V) SHDN1 or SHDN2 Pin Threshold (Off-to-On) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 –50 –25 0 50 25 0 75 TEMPERATURE (°C) 100 125 0 1 2 3 4 5 6 7 8 SHDN PIN VOLTAGE (V) 9 3028 G16 350 60 50 40 30 20 300 0.
PAGE 7
LT3028 U W TYPICAL PERFOR A CE CHARACTERISTICS Output 2 Input Ripple Rejection 80 70 70 60 60 50 COUT = 10µF 40 30 COUT = 1µF 20 I = 100mA L V = 2.3V + 50mVRMS RIPPLE 10 CIN2 = 0 BYP TJ = 25°C 0 0.1 0.01 1 10 FREQUENCY (kHz) 100 Output 2 Input Ripple Rejection 80 CBYP = 0.01µF 70 CBYP = 1000pF 50 CBYP = 100pF 40 30 20 I = 100mA L VIN2 = 2.3V + 50mVRMS RIPPLE 10 C OUT = 10µF TJ = 25°C 0 0.1 0.01 1 10 FREQUENCY (kHz) 1000 100 1000 60 50 40 30 20 VIN2 = VOUT2(NOMINAL) + 1V + 0.
PAGE 8
LT3028 U W TYPICAL PERFOR A CE CHARACTERISTICS Channel-to-Channel Isolation Channel-to-Channel Isolation Output 2 Load Regulation 0 90 –1 CHANNEL 2 80 –2 VOUT1 20mV/DIV 70 LOAD REGULATION (mV) CHANNEL-TO-CHANNEL ISOLATION (dB) 100 CHANNEL 1 60 50 VOUT2 20mV/DIV 40 GIVEN CHANNEL IS TESTED 30 WITH 50mVRMS SIGNAL ON OPPOSING CHANNEL, BOTH 20 CHANNELS DELIVERING FULL 10 CURRENT TJ = 25°C 0 100 1k 10k 10 FREQUENCY (Hz) –3 –4 –5 –6 –7 –8 100k COUT1 = 22µF 50µs/DIV COUT2 = 10µF CBYP1 = CBYP2 =
PAGE 9
LT3028 U W TYPICAL PERFOR A CE CHARACTERISTICS 10Hz to 100kHz Output Noise CBYP = 0pF 10Hz to 100kHz Output Noise CBYP = 1000pF 10Hz to 100kHz Output Noise CBYP = 100pF VOUT 100µV/DIV VOUT 100µV/DIV 1ms/DIV COUT = 10µF IL = FULL LOAD VOUT SET FOR 5V 3028 G42 10Hz to 100kHz Output Noise CBYP = 0.01µF VIN2 = 6V, VOUT2 SET FOR 5V 0.2 CIN2 = 10µF COUT2 = 10µF 0.1 T = 25°C J 0 –0.1 –0.
PAGE 10
LT3028 U U U PI FU CTIO S (DFN Package)/(TSSOP Package) GND (Pins 5, 17)/(Pins 1, 5, 8, 9, 16, 17): Ground. The Exposed Pad must be soldered to PCB ground for optimum thermal performance. ADJ1/ADJ2 (Pins 16/9)/(Pins 15/10): Adjust Pin. These are the inputs to the error amplifiers. These pins are internally clamped to ±7V. They have a bias current of 30nA which flows into the pin (see curve of ADJ1/ADJ2 Pin Bias Current vs Temperature in the Typical Performance Characteristics section).
PAGE 11
LT3028 U W U U APPLICATIO S I FOR ATIO than 1µA in shutdown. In addition to the low quiescent current, the LT3028 regulator incorporates several protection features which make it ideal for use in batterypowered systems. The device is protected against reverse input voltages. Additionally, in dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 20V and still allow the device to start and operate.
PAGE 12
LT3028 U W U U APPLICATIO S I FOR ATIO used to bypass the reference (for low noise operation), larger values of output capacitors are needed. For 100pF of bypass capacitance on Output 2, 2.2µF of output capacitor is recommended. With a 330pF bypass capacitor or larger on this output, a 3.3µF output capacitor is recommended. For Output 1, 4.7µF of output capacitor is recommended for 100pF of bypass capacitance. With 1000pF or larger bypass capacitor on this output, a 6.
PAGE 13
LT3028 U W U U APPLICATIO S I FOR ATIO Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients.
PAGE 14
LT3028 U W U U APPLICATIONS INFORMATION The power dissipated by each output will be equal to: IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX)) Where for Output 1: IOUT(MAX) = 500mA VIN(MAX) = 5V IGND at (IOUT = 500mA, VIN = 5V) = 9mA For Output 2: IOUT(MAX) = 100mA VIN(MAX) = 5V IGND at (IOUT = 100mA, VIN = 5V) = 2mA So for Output 1: P = 500mA (5V – 3.3V) + 9mA (5V) = 0.90W For Output 2: P = 100mA (5V – 2.5V) + 2mA (5V) = 0.
PAGE 15
LT3028 U U W U APPLICATIONS INFORMATION In circuits where a backup battery is required, several different input/output conditions can occur. The output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage or is left open circuit. When the IN pin of the LT3028 is forced below either OUT pin or either OUT pin is pulled above the IN pin, input current for the corresponding regulator will typically drop to less than 2µA.
PAGE 16
LT3028 U PACKAGE DESCRIPTIO DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) R = 0.115 TYP 5.00 ±0.10 (2 SIDES) R = 0.20 TYP 0.65 ±0.05 3.50 ±0.05 9 0.40 ± 0.10 16 3.00 ±0.10 (2 SIDES) 1.65 ±0.05 (2 SIDES) 1.65 ± 0.10 (2 SIDES) PACKAGE OUTLINE 2.20 ±0.05 PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH (DHC16) DFN 1103 8 0.200 REF 0.25 ± 0.05 0.50 BSC 4.40 ±0.05 (2 SIDES) 1 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 4.40 ±0.10 (2 SIDES) 0.00 – 0.