G760A

Global Mixed-mode Technology Inc. G760A Fan Speed PWM Controller Features Constant Fan Speed Control PWM control for stable operation Build-in MOSFET switch SMBus interface Internal short-circuit protection On/Off control provided General Description 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* G760A TEMP. RANGE 0°C to +70°C PIN-PACKAGE 8-SOP Pin configuration G760A OUT F.G. ON/OFF O N/OFF GND 1 2 3 4 8 7 6 5 V CC SMBDATA SMBCLKLK CLK 8Pin SOP Ver 4.3 Oct 28, 2002 TEL: 886-3-5788833 http://www.gmt.com.tw 1 Global Mixed-mode Technology Inc. Absolute Maximum Ratings PARAMETER Supply Voltage Operating Temperature Range Junction Temperature Range Storage Temperature Range Lead Temperature (solding) 10 seconds G760A MAXIMUM -0.3 to +7 0 to +70 0 to +125 -65 to +150 300 SYMBOL VCC TA TJ TSTG TL UNITS V °C °C °C °C Electrical Characteristics (Unless specified: VCC = 5V, TA = 25°C) PARAMETER 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 CONDITIONS VCC On/Off = 0V MIN 4.5 TYP 5 2 0.2 0.5 MAX 5.5 5 0.25 0.8 UNITS V µA Ω A V V mA V V V VIL VIH VCC=5V VCC=5V VCC=5V 2.4 350 1.8 0.7 1.1 Application Circuit 5V 10µF 3.3V to 5V VIN FG ON/OFF 10 µF * 1N4148 1 2 3 4 8 7 6 5 32.768KHz 10k 10k FAN Diode 1N4148 is optional Block Diagram OUT VCC FG PW M DUTY LOGIC FAN F AN CONTROL LOGIC ON/OFF SET_CNT ACT_CNT CLK FAN_STA SMBDATA SMBus CONTROL LOGIC SMBCLK Ver 4.3 Oct 28, 2002 TEL: 886-3-5788833 http://www.gmt.com.tw 2 Global Mixed-mode Technology Inc. Pin Description PIN NO. 1 2 3 4 5 6 7 8 G760A PIN FUNCTION PIN NAME OUT F.G. ON/OFF GND CLK SMBCLK SMBDATA VCC 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 Table 1. Count numbers for P=2 rpm 968 1935 2000 3000 4000 5000 6000 7000 8000 9000 10000 20000 30000 W hen 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. CLK=32768Hz --254 246 164 123 98 82 70 61 55 49 25 16 CLK=16384Hz 254 127 123 82 61 49 41 35 31 27 25 12 8 Ver 4.3 Oct 28, 2002 TEL: 886-3-5788833 http://www.gmt.com.tw 3 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 G760A 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 SMBCLK 1 9 1 9 SMBDATA 0 1 1 1 1 1 0 R/W 0 0 0 0 0 0 D1 D0 Start by Master Address Byte Ack by G760 9 1 Pointer Byte Ack by G760 9 1 0 1 1 1 1 1 0 R/W D7 D6 D5 D4 D3 D2 D1 D0 Repeat Start by Master Address Byte Ack by G760 Data Byte No Ack by Master Stop Cond by Master (a) Typical Pointer Set Followed by Immediate Read SMBCLK 1 9 1 9 SMBDATA 0 1 1 1 1 1 0 R/W D7 D6 D5 D4 D3 D2 D1 D0 Start by Master Address Byte Ack by G760 Data Byte No Ack Stop Cond by Master by Master (b) Typical 1-Byte Read with Preset Pointer SMBCLK 1 9 1 9 1 9 9 SMBDATA 0 1 1 1 1 1 0 R/W 0 0 0 0 0 0 D1 D0 0 1 1 1 1 1 0 R/W D7 D6 D5 D4 D3 D2 D1 D0 Start by Master Address Byte Ack by G760 Pointer Byte Ack by G760 Address Byte Ack by G760 Data Byte No Ack by Master Stop Cond by Master (a) Typical Pointer Set Followed by Immediate Read SMBCLK 1 9 1 9 1 9 SMBDATA Start by Master 0 1 1 1 1 1 0 R/W 0 0 0 0 0 0 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 Address Byte Ack by G760 Pointer Byte Ack by Master Configuration Byte Ack by G760 Stop Cond by Master (b) Register Write Ver 4.3 Oct 28, 2002 TEL: 886-3-5788833 http://www.gmt.com.tw 4 Global Mixed-mode Technology Inc. Package Information C G760A E H L D θ 7° (4X) A2 y B A1 A e 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. 1.35 0.10 ----0.33 0.19 4.80 3.80 ----5.80 0.40 ----0º DIMENSION IN MM NOM. 1.60 ----1.45 ----------------1.27 ----------------- MAX. 1.75 0.25 ----0.51 0.25 5.00 4.00 ----6.20 1.27 0.10 8º MIN. 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. Ver 4.3 Oct 28, 2002 TEL: 886-3-5788833 http://www.gmt.com.tw 5