Datasheet

ManualsBrandsMICROCHIP TECHNOLOGY ManualsPMICsPMIC - motor controllers Pre-driver - low-side Parallel SOIC 8

 2002-2012 Microchip Technology Inc. DS21446D-page 1

DTC646

Features

• Temperature Proportional Fan Speed for Acoustic

Control and Longer Fan Life

• Efficient PWM Fan Drive

• 3.0V to 5.5V Supply Range:

- Fan Voltage Independent of TC646

Supply Voltage

- Supports any Fan Voltage

• FanSense™

Fault Detection Circuits Protect

Against Fan Failure and Aid System Testing

• Shutdown Mode for "Green" Systems

• Supports Low Cost NTC/PTC Thermistors

• Space Saving 8-Pin MSOP Package

• Over-temperature Indication

Applications

• Power Supplies

• Computers

•File Servers

• Portable Computers

• Telecom Equipment

• UPS, Power Amps

• General Purpose Fan Speed Control

Available Tools

• Fan Controller Demonstration Board (TC642DEMO)

• Fan Controller Evaluation Kit (TC642EV)

Package Types

General Description

The TC646 is a switch mode, fan speed controller for

use with brushless DC fans. Temperature proportional

speed control is accomplished using pulse width mod-

ulation (PWM). A thermistor (or other voltage output

temperature sensor) connected to the V

input fur-

nishes the required control voltage of 1.25V to 2.65V

(typical) for 0% to 100% PWM duty cycle. The TC646

automatically suspends fan operation when measured

temperature (V

) is below a user programmed

minimum setting (V

). An integrated Start-up Timer

ensures reliable motor start-up at turn-on, coming out

of shutdown mode, auto-shutdown mode or following a

transient fault.

The TC646 features Microchip Technology's proprie-

tary FanSense™ technology for increasing system reli-

ability. In normal fan operation, a pulse train is present

at SENSE (Pin 5). A missing-pulse detector monitors

this pin during fan operation. A stalled, open, or uncon-

nected fan causes the TC646 to trigger its Start-up

Timer once. If the fault persists, the FAULT

output goes

low and the device is latched in its shutdown mode.

FAULT

is also asserted if the PWM reaches 100% duty

cycle, indicating a possible thermal runaway situation,

although the fan continues to run. See Section 5.0,

“Typical Applications”, for more information and system

design guidelines.

The TC646 is available in the 8-pin plastic DIP, SOIC

and MSOP packages and is available in the industrial

and extended commercial temperature ranges.

TC646

GND

FAULT

SENSE

OUT

SOIC/PDIP/MSOP

PWM Fan Speed Controller with Auto-Shutdown

and FanSense

™

Technology

Summary of content (30 pages)

PAGE 1
DTC646 PWM Fan Speed Controller with Auto-Shutdown and FanSense™ Technology Features • Temperature Proportional Fan Speed for Acoustic Control and Longer Fan Life • Efficient PWM Fan Drive • 3.0V to 5.
PAGE 2
TC646 Functional Block Diagram VIN + VOTF – VDD – OTF PWM + Control Logic VOUT CF 3 x TPWM Timer Clock Generator – VAS Start-up Timer + FAULT SHDN – Missing Pulse Detect. + – GND TC646 + VSHDN 10kΩ SENSE 70mV (typ.) DS21446D-page 2  2002-2012 Microchip Technology Inc.
PAGE 3
TC646 1.0 ELECTRICAL CHARACTERISTICS Absolute Maximum Ratings* Supply Voltage ......................................................... 6V Input Voltage, Any Pin..... (GND – 0.3V) to (VDD+0.3V) *Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of the specifications is not implied.
PAGE 4
TC646 DC ELECTRICAL SPECIFICATIONS (CONTINUED) Electrical Characteristics: Unless otherwise specified, TMIN  TA  TMAX, VDD = 3.0V to 5.5V Symbol Parameter Min Typ Max Units VC(MAX),VOTF Voltage at VIN for 100% Duty Cycle and Overtemp. Fault 2.5 2.65 2.8 V VC(SPAN) VC(MAX) - VC(MIN) 1.3 1.4 1.5 V VAS Auto-shutdown Threshold VC(MAX) ~ VC(SPAN) — VC(MAX) V VSHDN Voltage Applied to VIN to ensure Reset/Shutdown — — VDD x 0.
PAGE 5
TC646 2.0 PIN DESCRIPTIONS The descriptions of the pins are listed in Table 2-1. TABLE 2-1: Pin No. PIN FUNCTION TABLE Symbol Description 2.3 Analog Input (VAS) An external resistor divider connected to the VAS input sets the auto-shutdown threshold. Auto-shutdown occurs when VIN  VAS. The fan is automatically restarted when VIN (VAS + VHAS) (see Section 5.0, “Typical Applications”, for more details). 1 VIN Analog Input 2 CF Analog Output 2.4 GND denotes the ground terminal.
PAGE 6
TC646 3.0 DETAILED DESCRIPTION 3.5 3.1 PWM The TC646 detects faults in two ways: The PWM circuit consists of a ramp generator and threshold detector. The frequency of the PWM is determined by the value of the capacitor connected to the CF input. A frequency of 30 Hz is recommended (CF = 1 µF). The PWM is also the time base for the Start-up Timer (see Section 3.3, “Start-Up Timer”). The PWM voltage control range is 1.25V to 2.65V (typical) for 0% to 100% output duty cycle. 3.
PAGE 7
TC646 TC646 Status Normal Operation Normal Operation Auto-Shutdown Mode ShutDown Normal Operation HI 2.6V VAS + VHAS VAS TEMP. 1.2V tRESET VIN VREL VSHDN LO GND Time FIGURE 3-1: TC646 Nominal Operation. Entering shutdown mode also performs a complete device reset. Shutdown mode resets the TC646 into its power-up state. The Start-up and Fault Timers, and any current faults, are cleared. FAULT is unconditionally inactive in shutdown mode.
PAGE 8
TC646 4.0 SYSTEM BEHAVIOR The flowcharts describing the TC646’s behavioral algorithm are shown in Figure 4-1. They can be summarized as follows: 4.1 Power-Up (1) Assuming the device is not being held in auto-shutdown mode (VIN > VAS).......... (2) Turn VOUT output on for 32 cycles of the PWM clock. This ensures that the fan will start from a dead stop. 4.3 Fan Fault Fan fault is an infinite loop wherein the TC646 is latched in shutdown mode. This mode can only be released by a reset (i.e.
PAGE 9
TC646 Normal Operation Power-Up Clear Missing Pulse Detector Power-on Reset FAULT = 1 Yes VIN < VSHDN? Shutdown VOUT = 0 No Yes VIN > VREL? VIN < VSHDN? No No VIN > VREL No Yes Yes Yes VIN < VAS? AutoShutdown VOUT = 0 VIN < VAS? Auto Shutdown VOUT = 0 No No Yes Power-Up No VIN > (VAS + VHAS) Yes VIN > No (VAS + VHAS) VIN > VOTF? Yes No Yes Hot Start Shutdown VOUT = 0 FAULT = 0 Hot Start VOUT Proportional to VIN Fire Start-up Timer (1 SEC) No Fan Pulse Detected? Yes Fire Sta
PAGE 10
TC646 5.0 TYPICAL APPLICATIONS The TC642 demonstration and prototyping board (TC642DEMO) and the TC642 Evaluation Kit (TC642EV) provide working examples of TC646 circuits and prototyping aids. The TC642DEMO is a printed circuit board optimized for small size and ease of inclusion into system prototypes. The TC642EV is a larger board intended for benchtop development and analysis.
PAGE 11
TC646 5.1 Temperature Sensor Design EQUATION VDD x R2 The temperature signal connected to VIN must output a voltage in the range of 1.25V to 2.65V (typical) for 0% to 100% of the temperature range of interest. The circuit in Figure 5-2 illustrates a convenient way to provide this signal. VDD R1 = 100 kΩ NTC Thermistor 100 kΩ@25˚C VIN R2 = 23.2kΩ FIGURE 5-2: Circuit. Temperature Sensing Figure 5-2 shows a simple temperature dependent voltage divider circuit.
PAGE 12
TC646 5.3 VDD R1 One boundary condition which may impact the selection of the minimum fan speed is the irregular activation of the Diagnostic Timer due to the TC646 “missing” fan commutation pulses at low speeds. This is a natural consequence of low PWM duty cycles (typically 25% or less). Recall that the SENSE function detects commutation of the fan as disturbances in the current through RSENSE. These can only occur when the fan is energized (i.e., VOUT is “on”).
PAGE 13
TC646 Nominal Fan Current (mA) RSENSE () 50 9.1 100 4.7 150 3.0 200 2.4 250 2.0 300 1.8 350 1.5 400 1.3 450 1.2 500 1.0 Fan RBASE VOUT Q1 SENSE CSENSE (0.1 μF Typ.) RSENSE 5.5 SENSE Network. Tek Run: 10.0kS/s Sample [ T ] Waveform @ Sense Resistor GND 1 Waveform @ Sense Pin 90mV 50mV GND T 2 Ch1 100mV FIGURE 5-5: Ch2 100mV M5.00ms Ch1 142mV SENSE Waveforms. Table 5-1 lists the recommended values of RSENSE based on the nominal operating current of the fan.
PAGE 14
TC646 A base-current limiting resistor is required with bipolar transistors. This is shown in Figure 5-6. The correct value for this resistor can be determined as follows: VDD RBASE – RBASE + VBE(SAT)– +V = VRSENSE + VBE(SAT) + VRBASE VRSENSE = IFAN x RSENSE VRBASE = RBASE x IBASE IBASE = IFAN / hFE VOH is specified as 80% of VDD in Section 1.0, “Electrical Characteristics”; VBE(SAT) is given in the chosen transistor data sheet. It is now possible to solve for RBASE.
PAGE 15
TC646 +5V VDD R2* 2.2 kΩ VOUT D1 12.0V Zener Fan TC646 Q1* R4* 10 kΩ GND R3* 2.2Ω -12V NOTE: *Value depends on the specific application and is shown for example only. FIGURE 5-8: TABLE 5-2: Device MMBT2222A MPS2222A MPS6602 Power the Fan from a -12V Supply. TRANSISTORS AND MOSFETS FOR Q1 (VDD = 5V) Package Max. VBE(sat)/VGS (V) Min. HFE VCEO/VDS (V) Fan Current (mA) Suggested RBASE () SOT-23 1.2 50 40 150 800 TO-92 1.2 50 40 150 800 TO-92 1.
PAGE 16
TC646 Design Example Step 1. Calculate R1 and R2 based on using an NTC having a resistance of 10 k at TMIN (25°C) and 4.65 k at TMAX (45°C) (See Figure 5-9). R1 = 20.5 k R2 = 3.83 k Step 2. Set auto-shutdown level VAS = 1.8V. Limit the divider current to 100 µA from which R5 = 33 k R6 = 18 k Step 3. Design the output circuit. Maximum fan motor current = 250 mA. Q1 beta is chosen at 50 from which R7 = 800 . +5V +12V +5V Open-Drain Device NTC 10 kΩ @ 25˚C R1 20.
PAGE 17
TC646 +12V +5V (RESET) (Optional) Open-Drain I/O0 Outputs R1 110 kΩ (MSB) I/O1 R2 240 kΩ CMOS I/O2 Outputs R3 360 kΩ I/O3 (LSB) Analog or Digital Temperature Data from one or more Sensors CMOS Microcontroller R5 1.5 kΩ +5V +5V 1 V IN VDD 8 CB .01 μF + R7 R4 33 kΩ 18 kΩ +5V R 2 C F TC646 1 μF 3 8 18 kΩ CB VAS FAULT 6 .01 μF 4 R6 1 kΩ VOUT 7 GND SENSE 5 Fan + CB 1 μF R9 800Ω 2N2222A +5V R10 10 kΩ 0.1 μF R11 2.2Ω GND FIGURE 5-10: INT TC646 as a Microcontroller Peripheral.
PAGE 18
TC646 6.0 PACKAGING INFORMATION 6.1 Package Marking Information 8-Lead PDIP (300 mil) XXXXXXXX NNN YYWW TC646VPA 025 0215 8-Lead SOIC (150 mil) XXXXXXXX YYWW NNN 8-Lead MSOP XXXXXX YWWNNN Legend: XX...
PAGE 19
TC646 8-Lead Plastic Dual In-line (P) – 300 mil (PDIP) Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.
PAGE 20
TC646 8-Lead Plastic Small Outline (SN) – Narrow, 150 mil (SOIC) Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.
PAGE 21
TC646 8-Lead Plastic Micro Small Outline Package (MS) (MSOP) Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.com/packaging E p E1 D 2 B n 1  A2 A c  A1 (F) L  Number of Pins Pitch Overall Height MILLIMETERS* INCHES Units Dimension Limits n p MAX NOM MIN MIN NOM 0.65 .026 .044 A 1.18 .038 0.76 .006 0.05 .193 .200 .114 .118 .114 .118 L .016 .035 Foot Angle F  Lead Thickness c .
PAGE 22
TC646 6.
PAGE 23
TC646 7.0 REVISION HISTORY Revision D (December 2012) Added a note to each package outline drawing.  2002-2012 Microchip Technology Inc.
PAGE 24
TC646 NOTES: DS21446D-page 24  2002-2012 Microchip Technology Inc.
PAGE 25
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PAGE 26
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PAGE 27
TC646 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO.
PAGE 28
TC646 NOTES: DS21446D-page 28  2002-2012 Microchip Technology Inc.
PAGE 29
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PAGE 30
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