Datasheet

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LT3469

3469f

Amplifier

■

Current Limit: ±40mA Typical

■

Input Common Mode Range: 0V to 10V

■

Output Voltage Range: 1V to (V

– 1V)

■

Differential Gain Stage with High Impedance Output

Stage)

■

Quiescent Current (from V

): 2mA

■

Unloaded Gain: 30,000 Typical

Switching Regulator

■

Generates V

Up to 35V

■

Wide Operating Supply Range: 2.5V to 16V

■

High Switching Frequency: 1.3MHz

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Internal Schottky Diode

■

Tiny External Components

■

Current Mode Switcher with Internal Compensation

■

Low Profile (1mm) SOT-23 Package

Piezo Microactuator Driver

with Boost Regulator

■

Piezo Speakers

■

Piezo Microactuators

■

Varactor Bias

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

–

+IN

GND

LT3469

453k

16.5k

0.47µF

50V

OUT

1V TO 33V

PIEZO

ACTUATOR

5nF < C

300nF

10k

–

9.09k

100k

47µH

–IN

OUT

3469 TA03

5V OR 12V

INPUT

0V TO 3V

1µF

16V

The LT

3469 is a transconductance (g

) amplifier that can

drive outputs up to 33V from a 5V or 12V supply. An

internal switching regulator generates a boosted supply

voltage for the g

amplifier. The amplifier can drive

capacitive loads in the range of 5nF to 300nF. Slew rate is

limited only by the maximum output current. The 35V

output voltage capability of the switching regulator, along

with the high supply voltage of the amplifier, combine to

allow the wide output voltage range needed to drive a

piezoceramic microactuator.

The LT3469 switching regulator switches at 1.3MHz,

allowing the use of tiny external components. The output

capacitor can be as small as 0.22µF, saving space and cost

versus alternative solutions.

The LT3469 is available in a low profile ThinSOT

package.

ThinSOT is a trademark of Linear Technology Corporation.

Piezo Microactuator Driver

Response Driving a 33nF Load

OUT

100mA/DIV

OUT

10V/DIV

INPUT

5V/DIV

50µs/DIV

3469 TA04

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (8 pages)

PAGE 1
LT3469 Piezo Microactuator Driver with Boost Regulator U FEATURES DESCRIPTIO Amplifier ■ Current Limit: ±40mA Typical ■ Input Common Mode Range: 0V to 10V ■ Output Voltage Range: 1V to (V CC – 1V) ■ Differential Gain Stage with High Impedance Output (gm Stage) ■ Quiescent Current (from V ): 2mA CC ■ Unloaded Gain: 30,000 Typical The LT®3469 is a transconductance (gm) amplifier that can drive outputs up to 33V from a 5V or 12V supply.
PAGE 2
LT3469 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) VIN Voltage ............................................................. 16V SW Voltage ............................................................. 40V VCC Voltage............................................................. 38V +IN, –IN Voltage ..................................................... 10V FB Voltage ................................................................ 3V Current Into SW Pin ....................
PAGE 3
LT3469 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) VIN = 5V, VCC = 35V, unless otherwise noted. PARAMETER CONDITIONS Switch Leakage Current Diode VF Diode Reverse Leakage Current VSW = 5V ID = 100mA VR = 5V MIN Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
PAGE 4
LT3469 U W TYPICAL PERFOR A CE CHARACTERISTICS (gm Amplifier) Output Current vs Differential Input Voltage VCC Quiescent Current 2.5 100°C 250 –50°C 25 25°C 20 2.0 –50°C 1.5 1.0 0.
PAGE 5
LT3469 U OPERATIO gm Amplifier The LT3469 is a wide output voltage range gm amplifier designed to drive capacitive loads. Input common mode range extends from 10V to ground. The output current is proportional to the voltage difference across the input terminals. When the output voltage has settled, the input terminals will be at the same voltage; supply current of the amplifier will be low and power dissipation will be low.
PAGE 6
LT3469 U OPERATIO 90 + INPUT 80 VOUT gm EFFICIENCY (%) – R1 R2 CBOOST VIN = 12V VOUT = 35V 85 75 70 65 60 55 3469 F04 50 Figure 4. Boosting the Bandwidth of the gm Amplifier with Capacitance On the Inverting Input simply an amplified version of the difference between the feedback voltage and the reference voltage of 1.23V. In this manner, the error amplifier sets the correct peak current level to keep the output in regulation.
PAGE 7
LT3469 U OPERATIO input, power dissipation is calculated from the amplifier quiescent current (IQ), input frequency (f), output swing (VOUT(P-P)), capacitive load (CL), amplifier supply voltage (VCC) and switching regulator efficiency (η) as follows: as short as possible. To prevent electromagnetic interference (EMI) problems, proper layout of the high frequency switching path is essential. The voltage signal of the SW pin has sharp rise and fall edges.
PAGE 8
LT3469 U PACKAGE DESCRIPTIO TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.52 MAX 0.65 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 ID 0.22 – 0.36 8 PLCS (NOTE 3) 0.65 BSC RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.80 – 0.90 0.09 – 0.20 (NOTE 3) 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 1.