Linear Technology Chronicle High Performance Analog Solutions from Linear Technology
Vol. 13 No. 3
Focus…
Motor/Motion Control LTC®3708/LT®1976 24V to 3.3V and 1.8V Power
LTC2904 Supervisor
Motor Drive Circuitry
Power Stage
DSP/µC
LT1630
Motor
Sensors and Signal Conditioning
Inside This Issue: • Current Monitoring in Motor Control Applications • Digitizing Encoder Signals • Front-End Signal Conditioning Op Amp • FET Drivers • Dual Output Step-Down Controller • High Voltage Buck Regulator • Pin-Configurable Dual Power Supply Monitor
The continual demand for smaller, more efficient motors is driving the need for lower-power, efficient, precision integrated circuits in space-saving packages. Powerful inexpensive microcontrollers and DSPs, combined with advances in digital control, have fueled the growth of motor and motion control electronics. Though digital control holds promise for the future, there is still significant need for precision analog circuitry for signals that need amplifying, filtering and converting into usable digital information.
Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more
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LTC1407 T/H ADC T/H
Linear Technology strives to stay abreast of the motor and motion control market needs, providing integrated circuits for next generation control systems. The result is devices that provide efficient power conversion, accurate signal conditioning, voltage monitoring and high-resolution data conversion. The following pages highlight devices targeted for industrial motors and motion control applications.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT and No RSENSE are trademarks of Linear Technology information, visit our webCorporation. site at www.linear.com.
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Motor Control–Monitoring Multiphase Currents Complex control algorithms available with today’s powerful DSPs/µCs can give AC motors (which are often much more efficient than their DC counterparts) some of the performance advantages of DC motors, such as high torque at slow speed and accurate variable speed control. An example of this is sensorless vector control of 3-phase motors. By monitoring the stator currents, the rotor currents are calculated without using feedback sensors. Precise timing for proper electronic commutation is obtained along with independent control of speed and torque.
2-Channel Simultaneous Sampling SAR ADC 3V
CHO+ CHO2 Differential Simultaneous Sampling Input Channels CHI+ CHI-
The new LTC1407, 2-channel simultaneous sampling successive approximation register ADC is ideal for 3-phase motor control. Using this device, two current phases can be digitized simultaneously, preserving the phase information of the signals to provide precise control of motor torque. Alternatively, two LTC1407 ICs can digitize three phases plus monitor the ground return (for a ground fault) or an auxiliary input. Key features include: • SAR architecture – zero latency conversions • 1.5Msps/channel throughput • Two differential inputs and two T/Hs for simultaneous sampling • Small 10-pin MSOP package • 3.3V operation
LTC1407 14-Bit, 3Msps ADC
3-Wire SPI Serial I/O MSOP-10
2.5V Ref
14-Bit and 12-Bit Motor Control ADCs Part Number LTC1403
Resolution
Differential Input Signal
Simultaneous Sampling
12 Bits
Unipolar
No, 1-Ch
LTC1403-1
12 Bits
Bipolar
No, 1-Ch
LTC1407
12 Bits
Unipolar
Yes, 2-Ch
LTC1407-1
12 Bits
Bipolar
Yes, 2-Ch
Unipolar
Yes, 2-Ch
LTC1407A
14 Bits
Select the resolution and input range that’s right for your application!
LTC1407A-1
14 Bits
Bipolar
Yes, 2-Ch
LTC1403A
14 Bits
Unipolar
No, 1-Ch
For single applications with sample rates to 2.8Msps, see the new 14-bit/12-bit LTC1403A/LTC1403.
LTC1403A-1
14 Bits
Bipolar
No, 1-Ch
Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear.com. 2
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Motion Control–Digitizing Sine Wave Encoder Signals Motion control is another application for the LTC1407. For high resolution and precise positioning, sine encoders output an analog waveform instead of digital pulses. The sine waves can be digitized to 12-bit resolution providing additional position accuracy to an encoder that may already provide 1024 or 2048 lines of resolution. For these applications, the dual channel LTC1407 is ideal. At 1.5Msps per channel, the device can monitor the angular position of rotating shafts by digitizing the sine and cosine encoder outputs to provide the phase angle/position and direction of the motor. The 3-wire
serial interface (which is compatible with standard microcontrollers and DSPs) not only keeps the layout small, but also simplifies routing and reduces data bus noise when compared with a parallel 16-bit wide data bus. Key features of the LTC1407 are: • 1.5Msps conversion rate/channel • 80dB common mode rejection (at fIN=100kHz) • Serial interface compatible with popular DSPs and microcontrollers • 200ps aperture delay matching between channels
LTC1407 Is Ideal for Encoder Applications
VDD
Sine
LTC1407 S/H ADC S/H
Cosine
Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear.com.
Linear Technology Chronicle
3
Front-End Signal Conditioning Op Amp Due to the harsh operating environment, high-resolution motion and motor control systems present unique design challenges. Signal conditioning requirements may include filtering (lowpass, bandpass, highpass or notch) amplification and level shifting. Key requirements for the front-end often include good common mode rejection, excellent AC performance and/or low temperature drift. The amplifier also must settle quickly to maintain 12-bit (LTC1407) or 14-bit (LTC1407A) performance at the rated converter speed. The amplifier selected for the ADC front-end will vary depending on the design’s specific criteria. The table below lists a selection of devices that are recommended for the LTC1407.
Using the LTC1630 to Level-Shift and Attenuate a Bipolar Input Signal 3.3V
3k
LT1630
10k
+
±5V
IN+
– 10k 3k IN-
LT1461A 2.5V Reference
LTC1407
REF
Amplifiers Well-Suited to the LTC1407 Part Number
Gain-Bandwidth Product (MHz)
LT1630
30
Dual, Good AC Performance, 500µV Offset Voltage, 3.5mA/Amplifier, Good Common Mode Rejection (LT1631 Quad Version)
LT1632
45
Dual, Good AC Performance, 1.5mV VOS, 4.3mA/Amplifier, Good Common Mode Rejection (LT1633 Quad Version)
LT1801
80
Dual, 350µV Offset Voltage, Good Common Mode Rejection, 2mA/Amplifier
LT6203
100
Dual, Low 1.9nV/√Hz Voltage Noise, 3mA/Amplifier
LT6600-2.5/-10
N/A
Differential In/Out Amplifier Plus 4th Order Lowpass Filter; Low Distortion, User-Selectable Common Mode Output
Comments
Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear.com. 4
Linear Technology Chronicle
FET Drivers Several factors go into the selection of drivers for the power stage. The type of motor, its speed and power requirements are parameters that affect the power stage voltage requirements, which can range from a few volts up to hundreds of volts. Linear Technology has a family of dual and quad FET drivers for motor control applications. An example is the LTC1693-1. This device is a dual FET driver that provides up to 1.5A peak drive current and a fast 16ns rise/fall time to minimize switching losses. Another dual FET driver, the LT1160, is for high voltage applications up to 60V.
LT1160 Motor Drive Application-Unidirectional Rotation HV LT1160
12V
SV+
BOOST
PV+
T GATE DR T GATE FB T SOURCE
IN TOP
B GATE DR
IN BOTTOM
B GATE FB PGND
FET Drivers for DC Motors, Stepper Motors and Brushless Motor Control Applications Part Number Half Bridge
Supply Voltage (Gate Drive)
LTC1693-1
4.5V to 13.2V
LTC1155 LT1158 LT1160 LT1161 LT1336
9V to 24V 4.5V to 30V 9V to 60V 8V to 60V 9V to 60V
Notes
DC/DC Converter
16ns with 1000pF Load; 180ns Transition Time with CLOAD = 10,000pF
-
tON for VGATE=VDD+5V = 180ns (CLOAD =1000pF); Micropower
Onboard Charge Pump
150ns Transition Time with CLOAD = 3,000pF
Onboard Charge Pump
Gate Drive Voltage Bootstrapped from High Voltage Rail
-
tON for VGATE=VDD+8V = 220µs (CLOAD =1000pF)
Onboard Charge Pump
180ns Transition Time with CLOAD = 10,000pF
Internal Boost Regulator
tON for VGATE=VDD+5V = 180ns (CLOAD =1000pF); Micropower
Onboard Charge Pump
Gate Drive Voltage Bootstrapped from High Voltage Rail
-
Full Bridge LTC1156 LT1162
4.5V to 18V 8V to 60V
Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear.com.
Linear Technology Chronicle
5
Dual Output Step-Down Controller with Voltage Tracking As core and I/O voltages continue to drop and system-level features are added that provide more functionality at the expense of more power, the increased design complexity provides additional challenges to the power supply design. In response, Linear Technology has added more functionality to its ICs to help simplify the design process. The new dual output LTC3708 controller is a good example. The device features 2-phase operation which reduces peak input
currents and reduces output noise. It can provide upwards of 20A of current per output, ideal for generating core and I/O supplies. The low reference voltage allows output voltages down to 0.6V. To handle power-up and power-down concerns, the device integrates a tracking feature that controls the ramp-up and ramp-down of the two supplies. By controlling the voltage at the power supply feedback nodes, the supplies can be ramped together or sequentially
adding an extra layer of control to your system. Features include: • • • • •
Dual output with 2-phase operation Small, 5mm x 5mm QFN package Up to 36V input supply voltage Fast transient response Low duty factor operation for large input/output voltage differentials • Programmable power-up/powerdown voltage tracking
High Efficiency Dual Output Step-Down Converter VIN 3.3V TO 28V
5V
10F 50V ×4
+ VOUT1 2.5V 15A
DRVCC PGOOD VCC TG1 TG2 BOOST2 BOOST1
L1 1.5H 330F 4V ×2
SW1 SENSE1+
+
BG1
LTC3708
SENSE1– PGND1
L2 1.2H
SW2 SENSE2+
+
BG2 SENSE2– PGND2
VFB1 VFB2 TRACK2 FCB ION1 ION2 ITH1 ITH2 INTLPF EXTLPF RUN/SS TRACK1 VRNG2 SGND VRNG1
VIN
470F 2.5V ×2
VOUT2 1.8V 15A
VIN
5V
Step-Down Controllers for Motor Motion Control Boards Part Number
Input Voltage Range
2-Phase Operation
Number of Outputs
LTC1778
4V - 36V
No
1
No RSENSE™ operation. Low Duty Cycle Operation with Excellent Transient Response
LTC3778
4V – 36V
No
1
Optional RSENSE Operation. Low Duty Cycle Operation with Excellent Transient Response
LTC3708
4V – 36V
Yes
2
Low Duty Cycle Operation with Excellent Transient Response, Output Tracking for Controlled Power-Up/Power-Down Operation
LTC3728L
4V – 30V
No
2
Constant Frequency Current Mode Architecture
Notes
Visit www.linear.com for a complete list of controllers.
Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear.com. 6
Linear Technology Chronicle
High Voltage Buck Regulator for Harsh Environments Moving machinery, motors, lighting and other electromechanical systems radiate noise and also inject noise back on the power supply. Inductive kicks can cause a nominal 24V system to momentarily peak well above the power supply’s rated voltage. Instead of designing additional protection around the power supply, a more cost-effective solution is to simply select an IC that can tolerate the higher voltages.
14V to 3.3V Step-Down Converter with 100µA No Load Quiescent Current VIN 3.3V TO 60V
4.7F 100V
BOOST 33H
SHDN
VOUT 3.3V 1A
SW
LT1976 CSS
VC
VBIAS
Linear Technology’s high voltage power products are ideal for such applications. With voltage ratings as high as 100V, these devices inherently provide protection against voltage spikes. The LT1976, for example, is a high voltage current mode step-down regulator that operates with input voltages from 3.3V to 60V for harsh environments. It includes a 1.5A peak current switch, draws only 100µA quiescent current and features a 1µA shutdown mode. Highlights of the LT1976 include: • Buck regulator with integrated power switch • 1.5A peak current switch • Input voltage up to 60V • 200kHz switching frequency • Thermally-enhanced TSSOP-16 package
VIN
CT SYNC GND
FB
100F 6.3V
PGFB PG
High Voltage Buck Switching Regulators Part Number
Input Voltage Range
Peak Switch Current
Quiescent Current
Switching Frequency
LT1976
3V – 60V
1.5A
100µA
200k
LT3430
5.5V – 60V
3A
2.5mA
200k
LT3434
3V – 60V
3A
100µA
200k
LTC3703
9.3V – 100V
N/A - ext. FET
1.7mA
to 600k
Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear.com.
Linear Technology Chronicle
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Pin-Configurable Dual Power Supply Monitor The LTC2904 provides a compact solution for monitoring dual power supplies. Available in a small 3mm x 2mm DFN package, it guarantees a valid reset signal with the power supply as low as 1V, extending system control as the power supplies ramp. Three-state logic allows a single device to monitor a range of power supply voltages. Instead of stocking a host of devices, a single device can now be used for many applications. It also allows the reset threshold tolerance to be set to one of three values: 5%, 7.5% or 10%. Features include: • Dual 1.5% accurate reset thresholds • Reset guaranteed valid with supplies down to 1V • 9 pin-programmable reset threshold combinations available
Supply Monitor ICs Part Number
Supply Monitors
Package
Notes
LTC2906
2
3mm x 2mm DFN, ThinSOT ™
3 Pin-Programmable Reset Thresholds and Tolerances, One Adjustable Supply Monitor
LTC2907
2
3mm x 2mm DFN, ThinSOT
3 Pin-Programmable Reset Thresholds and Tolerances; Adjustable Reset Time Delay, One Adjustable Supply Monitor
LTC2904
2
3mm x 2mm DFN, ThinSOT
9 Pin-Programmable Reset Thresholds, 3 Programmable Tolerances
LTC2905
2
3mm x 2mm DFN, ThinSOT
9 Pin-Programmable Reset Thresholds, 3 Programmable Tolerances, Adjustable Reset Time Delay
LTC1326
3
MSOP-8
Manual Push-Button Reset
LTC2903-1
4
ThinSOT
Reset Guaranteed Valid with 0.5V Supply
LTC2900-1
4
3mm x 3mm DFN, MSOP
16 User-Selectable Options; Open-Drain Reset Output
LTC2900-2
4
3mm x 3mm DFN, MSOP
16 User-Selectable Options; Push-Pull Reset Output
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Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear.com. 8
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