G760A Global Mixed-mode Technology Inc. Fan Speed PWM Controller Features General Description Constant Fan Speed Control PWM control for stable operation Build-in MOSFET switch SMBus interface Internal short-circuit protection On/Off control provided G760 is a single chip solution for fan speed control, packaged in a space saving SO-8 package. It connects directly to the fan and performs closed-loop control of the fan speed. The only external component required is a 10µF capacitor. It determined the current fan speed based on the fan rotation pulses and an externally supplied clock. It uses pulse width modulation (PWM) method and an on-chip MOSFET to control the fan speed to ±2% of the programmed speed. The desired fan speed is programmed via the SMBus. The actual fan speed and fan status can be read via the SMBus. Short-circuit protection is implemented to prevent damages to the fan and this IC itself. An On/Off control pin is also provided. Applications Notebook PC Industrial PC LAN Switch Servers Telecom equipment Industrial Control Ordering Information PART* TEMP. RANGE PIN-PACKAGE G760A 0°C to +70°C 8-SOP Pin configuration G760A OUT 1 8 V CC F.G. 2 7 SMBDATA ON/OFF 3 6 SMBCLKLK GND 4 5 CLK 8Pin SOP TEL: 886-3-5788833 http://www.gmt.com.tw Ver 4.3 Oct 28, 2002 1 G760A Global Mixed-mode Technology Inc. Absolute Maximum Ratings PARAMETER SYMBOL MAXIMUM UNITS VCC TA TJ TSTG TL -0.3 to +7 0 to +70 0 to +125 -65 to +150 300 V °C °C °C °C Supply Voltage Operating Temperature Range Junction Temperature Range Storage Temperature Range Lead Temperature (solding) 10 seconds Electrical Characteristics (Unless specified: VCC = 5V, TA = 25°C) PARAMETER CONDITIONS MIN TYP MAX UNITS VCC On/Off = 0V 4.5 5 2 0.2 0.5 5.5 5 0.25 V µA Ω A V V mA V V V Supply voltage Shutdown current MOSFET on resistance Short-circuit current limit Input logic low Input logic high Average Output current FG input Positive-going threshold voltage FG input Negative-going threshold voltage FG input Hysteresis voltage VIL VIH 0.8 2.4 350 VCC=5V VCC=5V VCC=5V 1.8 0.7 1.1 Application Circuit 5V VIN FAN FG ON/OFF 10 µF 1 8 2 7 3 6 4 5 10µF 3.3V to 5V 10k 10k 32.768KHz * 1N4148 Diode 1N4148 is optional Block Diagram OUT VCC PW M DUTY LOGIC FG FAN SET_CNT CONTROL LOGIC ON/OFF CLK ACT_CNT FAN_STA SMBus CONTROL LOGIC SMBDATA SMBCLK TEL: 886-3-5788833 http://www.gmt.com.tw Ver 4.3 Oct 28, 2002 2 G760A Global Mixed-mode Technology Inc. Pin Description PIN NO. PIN NAME 1 2 3 4 5 6 7 8 OUT F.G. ON/OFF GND CLK SMBCLK SMBDATA VCC PIN FUNCTION PWM output, connect to fan FAN pulse Input ON/OFF control pin, 0V means shutdown Ground Clock input for fan speed measurement SMBus clock line SMBus data line Supply voltage Description The fan speed is measured by counting the number of the CLK pin period between the rising edges of two fan speed pulses on FG pin. In this way, we are actually measuring the period of the fan speed. To avoid the cost of doing division to obtain the speed, this count number, N, is used in the PWM control algorithm, thus, the desired fan speed should be programmed by writing the corresponding count number. The count number is given by: N = (CLK x 30) / (rpm x P) N : Count Number P : FG pulses number per revolution of fan. For CLK = 32768Hz, P = 2 ⇒N = 491520 / rpm For CLK = 16384Hz, P = 2 ⇒N = 245762 / rpm Some selected count numbers are shown below When pin 3 (On/Off) is a logical 1, the fan speed will be controlled according to the setting in the programmed fan speed register. There are two ways to stop the fan, (1)setting pin 3 (On/Off) to 0V, (2) program the fan speed register to 255. These also makes the fan controller into power saving mode. Controlling Fan at Lower Speed For stably controlling fans at lower rotation speed, three schemes are recommended as below: 1.Use larger decoupling capacitors between FAN_OUT and GND. 2.Shunt a capacitor of 1µF-2µF on FG pin to GND. 3.Use fans with open-collector FG outputs. When controlling fans under lower rotation speed, the output voltage of FAN_OUT would be too low for fan to generate recognizable FG signals. Using decouple capacitors on FAN_OUT and FG is to increase the SNR on FG pins. While using fans with open_collector FG outputs can thoroughly solve the problem, because the logic high level of FG would be fixed to 5V. Table 1. Count numbers for P=2 rpm CLK=32768Hz CLK=16384Hz 968 1935 2000 3000 4000 5000 6000 7000 8000 9000 10000 20000 30000 --254 246 164 123 98 82 70 61 55 49 25 16 254 127 123 82 61 49 41 35 31 27 25 12 8 TEL: 886-3-5788833 http://www.gmt.com.tw Ver 4.3 Oct 28, 2002 3 G760A Global Mixed-mode Technology Inc. Internal Registers This IC provides 3 SMBus registers. 1.Programmed fan speed register:(SET_CNT,address:00b) This register is a read/write register, it contains the count number of the desired fan speed. Power up default is FFh. 2.Actual fan speed register: (ACT_CNT, address: 01b) This register is read only. It contains the count number of the actual fan speed. Power up default is FFh. 3.Fan status register: (FAN_STA , address : 10b) This register is read only. Its bit 0 is set to 1 when the actual fan speed is ±20% outside the desired speed. Its bit 1 is set to 1 when fan speed is below 1920 rpm. Power up default is 10b. SMBus Address The SMBus address of this chip is fixed to7Ch (01111100b) for write and 7Dh(01111101b) for read. SMBus Timing 1 SMBCLK SMBDATA 1 0 1 1 Start by Master 1 0 R/W 1 Address Byte 1 Repeat Start by Master 1 1 1 0 0 0 0 0 D1 D0 Ack by G760 Pointer Byte 9 D7 R/W D6 D5 D4 Ack by G760 Address Byte 0 0 1 9 1 9 Ack by G760 1 0 1 9 D2 D3 D1 D0 No Ack by Master Data Byte Stop Cond by Master (a) Typical Pointer Set Followed by Immediate Read 1 SMBCLK SMBDATA 1 9 0 1 1 1 1 Start by Master 1 9 D7 0 R/W D6 D5 D4 Ack by G760 Address Byte D2 D3 D1 D0 No Ack Stop Cond by Master by Master Data Byte (b) Typical 1-Byte Read with Preset Pointer SMBCLK SMBDATA 9 1 0 1 Start by Master 1 1 1 1 0 R/W 1 9 0 0 0 Ack by G760 Address Byte 0 0 0 D1 1 D0 9 0 1 1 Ack by G760 Pointer Byte 1 1 1 0 9 D7 D6 R/W D4 D5 Ack by G760 Address Byte D3 D2 Data Byte D1 D0 No Ack by Master Stop Cond by Master (a) Typical Pointer Set Followed by Immediate Read 1 SMBCLK SMBDATA 0 Start by Master 9 1 1 1 1 1 Address Byte 0 R/W Ack by G760 1 0 9 0 0 0 0 0 D1 Pointer Byte D0 1 D7 Ack by Master 9 D6 D5 D4 D3 D2 D1 Configuration Byte D0 Ack by G760 Stop Cond by Master (b) Register Write TEL: 886-3-5788833 http://www.gmt.com.tw Ver 4.3 Oct 28, 2002 4 G760A Global Mixed-mode Technology Inc. Package Information C E H L D θ 7° (4X) A2 y A A1 e B Note: 1. Package body sizes exclude mold flash and gate burrs 2. Dimension L is measured in gage plane 3. Tolerance 0.10mm unless otherwise specified 4. Controlling dimension is millimeter converted inch dimensions are not necessarily exact. SYMBOL A A1 A2 B C D E e H L y θ MIN. DIMENSION IN MM NOM. MAX. MIN. 1.35 0.10 ----0.33 0.19 4.80 3.80 ----5.80 0.40 ----0º 1.60 ----1.45 ----------------1.27 ----------------- 1.75 0.25 ----0.51 0.25 5.00 4.00 ----6.20 1.27 0.10 8º 0.053 0.004 ----0.013 0.007 0.189 0.150 ----0.228 0.016 ----0º DIMENSION IN INCH NOM. 0.063 ----0.057 ----------------0.050 ----------------- MAX. 0.069 0.010 ----0.020 0.010 0.197 0.157 ----0.244 0.050 0.004 8º Taping Specification Feed Direction Typical SOP Package Orientation GMT Inc. does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and GMT Inc. reserves the right at any time without notice to change said circuitry and specifications. TEL: 886-3-5788833 http://www.gmt.com.tw Ver 4.3 Oct 28, 2002 5