Datasheet

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LTC1844 Series

1844fa

150mA, Micropower,

Low Noise, VLDO

Linear Regulator

■

Very Low Dropout:

90mV at 150mA

30mV at 50mA (LTC1844-3.3)

■

Wide Input Voltage Range: 1.6V to 6.5V

■

Low 35µA Supply Current, Even in Dropout

■

Low Noise: 60µV

RMS

(10Hz to 100kHz)

■

±1.75% Voltage Accuracy Over Temperature,

Voltage and Current Ranges

■

Fast Transient Response

■

10nA Supply Current in Shutdown

■

Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 2.8V, 3.3V

■

Adjustable Output Voltage: 1.25V to 6V

■

Output Current Limit

■

Reverse-Battery and Reverse-Current Protection

■

No Protection Diodes Needed

■

Stable with 1µF Output Capacitor

■

Stable with Ceramic Capacitors

■

Short-Circuit and Thermal Overload Protection

■

Low Profile (1mm) SOT-23 Package

Fixed Voltage Low Noise, VLDO Linear Regulator

■

Portable Instruments and Battery-Powered Systems

■

Bluetooth/802.11 Cards

■

Cellular Phones

■

PDAs and Notebook Computers

The LTC

1844 Series are low noise VLDO

(very low

dropout) linear regulators designed for low power/portable

applications. These regulators can operate from input

voltages as low as 1.6V. Typical output noise is only

30µV

RMS

and typical dropout for the LTC1844-3.3 is just

90mV at the maximum load current of 150mA, reducing to

30mV at 50mA.

The internal P-channel MOSFET pass transistor requires

no base current, allowing the device to draw only 35µA

during normal operation, independent of the dropout

voltage and load current. The quiescent current falls to a

negligible 10nA during shutdown.

Other features include high output voltage accuracy,

excellent transient response, stability with ultralow ESR

ceramic capacitors as small as 1µF, reverse-battery and

reverse-current protection, short-circuit and thermal

overload protection and output current limiting.

The LTC1844 regulators are available in a low profile

(1mm) SOT-23 (ThinSOT

) package.

SHDN

1844 TA01

1µF

LTC1844-3.3

OUT

3.3V

3.3V TO 6.5V

BYP

GND

0.1µF

1µF

OFF ON

LTC1844-3.3 Dropout Voltage vs Load Current

OUT

(mA)

DROPOUT VOLTAGE (mV)

120

100

50 75 100

1844 TA02

125 150

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

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

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
LTC1844 Series 150mA, Micropower, Low Noise, VLDO Linear Regulator U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Very Low Dropout: 90mV at 150mA 30mV at 50mA (LTC1844-3.3) Wide Input Voltage Range: 1.6V to 6.5V Low 35µA Supply Current, Even in Dropout Low Noise: 60µVRMS (10Hz to 100kHz) ±1.75% Voltage Accuracy Over Temperature, Voltage and Current Ranges Fast Transient Response 10nA Supply Current in Shutdown Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 2.8V, 3.3V Adjustable Output Voltage: 1.
PAGE 2
LTC1844 Series W W W AXI U U ABSOLUTE RATI GS (Note 1) Supply Voltage (IN) ....................................... – 7V to 7V Input Voltage SHDN, BYP, ADJ .................................... – 0.3V to 7V Output Voltage OUT ........................................................ – 0.3V to 7V OUT to IN .................................................. – 7V to 7V Output Short-Circuit Duration ......................... Indefinite Operating Junction Temperature Range (Notes 2, 10) .....................
PAGE 3
LTC1844 Series ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT + 0.5V, unless otherwise noted. (Note 2) SYMBOL VADJ ∆VLNR PARAMETER ADJ Pin Voltage (Notes 3, 5) Line Regulation (Notes 3, 5) CONDITIONS ∆VDO Dropout Voltage (Notes 6, 7) MAX UNITS VIN = 2.0V to 6.5V, IOUT = 0mA to 150mA VIN = 2.2V to 6.5V, IOUT = 0mA to 150mA VIN = 2.0V to 6.5V, IOUT = 0mA to 100mA ● ● –1.50 –2.
PAGE 4
LTC1844 Series ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT + 0.5V, unless otherwise noted. (Note 2) SYMBOL PARAMETER ILIM Output Current Limit en Output Voltage Noise VSHDN SHDN Input Threshold tDELAY Shutdown Exit Delay CONDITIONS MIN TYP MAX UNITS LTC1844-1.
PAGE 5
LTC1844 Series U W TYPICAL PERFOR A CE CHARACTERISTICS VOUT vs Temperature VOUT vs Temperature 1.820 VOUT = 1.5V VOUT vs Temperature 2.520 VOUT = 1.8V 1.815 2.515 1.510 1.810 2.510 1.505 1.805 2.505 1.500 VOUT (V) 1.515 VOUT (V) VOUT (V) 1.520 1.800 1.795 2.495 1.490 1.790 2.490 1.485 1.785 2.485 0 50 75 25 TEMPERATURE (°C) 100 1.780 – 50 – 25 125 0 50 75 25 TEMPERATURE (°C) 100 1844 G01 2.480 – 50 – 25 125 VOUT = 2.8V VOUT = 3.3V 2.810 3.310 1.260 2.805 3.
PAGE 6
LTC1844 Series U W TYPICAL PERFOR A CE CHARACTERISTICS RMS Output Noise vs Load Current (10Hz to 100kHz) Input Ripple Rejection vs Frequency 300 100 60 COUT = 10µF 90 CBYP = 1000pF IL = 100µA 80 RIPPLE REJECTION (dB) CBYP = 0µF 200 150 100 CBYP = 0.1µF 50 RIPPLE REJECTION (dB) 250 OUTPUT NOISE (µVRMS) Input Ripple Rejection vs Temperature 70 60 50 40 30 20 50 40 30 20 10 10 0 0.01 0.
PAGE 7
LTC1844 Series U W U U APPLICATIO S I FOR ATIO The LTC1844 family are a series of 150mA ultralow dropout regulators with micropower quiescent current and shutdown. The devices are capable of supplying 150mA at a dropout voltage of 90mV (LTC1844-3.3, see Electrical Characteristics for dropout voltage of other versions). Output voltage noise is as low as 30µVRMS over a 10Hz to 100kHz bandwidth with the addition of a 0.1µF bypass capacitor.
PAGE 8
LTC1844 Series U W U U APPLICATIO S I FOR ATIO output current change of 1mA to 100mA is – 4mV typical at VOUT = 1.25V. At VOUT = 5V, load regulation is: (5V/1.25V)(– 4mV) = –16mV Because the ADJ pin is relatively high impedance (depending on the resistor divider used), stray capacitance at this pin can introduce significant phase shift in the error amplifier loop. The PCB layout should be designed to absolutely minimize the capacitance seen at the ADJ pin.
PAGE 9
LTC1844 Series U U W U APPLICATIONS INFORMATION temperature and applied voltage. The most common dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but exhibit strong voltage and temperature coefficients as shown in Figures 4 and 5. When used with a 5V regulator, a 10µF Y5V capacitor can exhibit an effective value as low as 1µF to 2µF over the operating temperature range.
PAGE 10
LTC1844 Series U U W U APPLICATIONS INFORMATION Thermal Considerations The power dissipated by the device will be equal to: The power handling capability of the device will be limited by the maximum rated junction temperature (125°C). The power dissipated by the device will be the output current multiplied by the input/output voltage differential: (IOUT)(VIN – VOUT). The LTC1844 series regulators have internal thermal limiting designed to protect the device during momentary overload conditions.
PAGE 11
LTC1844 Series 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 externally while the input is either pulled to ground, pulled to some intermediate voltage or left open circuit. The LTC1844 features reverse current protection to limit current draw from any supplementary power source at the output. When VIN is pulled to ground or is left open circuit, IIN and IOUT are less than 0.
PAGE 12
LTC1844 Series U PACKAGE DESCRIPTIO S5 Package 5-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1635) 0.62 MAX 0.95 REF 2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 TYP 5 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4.