LTC1840 Dual Fan Controller with 2-Wire Interface FEATURES DESCRIPTIO n Two 8-Bit Current DACs The LTC 1840 is a fan controller with two 8-bit current n DACs Guaranteed Monotonic output DACs, two tachometer interfaces, and four general n Known IC State on Power-Up purpose I/O (GPIO) pins. It operates from a single supply n Serial Interface Watchdog Timer with Disable with a range of 2.7V to 5.75V. A current output DAC is used TM 2 n 2-Wire Serial Interface Compatible with I C to control an external switching regulator, which controls and SMBus the fan speed. A current output DAC and tachometer allow n 2 Programmable Fan Tachometer Interfaces a controller to form a closed control loop on fan velocity. n 4 Programmable General Purpose I/Os The GPIO pins can be used as digital inputs or open drain n Small 16-Pin SSOP Package pull-down outputs. n Single 2.7V to 5.75V Supply Operation 2 The part features a simple 2-wire I C and SMBus compat- n Fault Output Signal ible serial interface that allows communication between n Status Register many devices. The interface includes a fault status register n Fan Blasting Function that reflects the state of the part and which can be polled n Nine Addresses Using Two Programming Lines to find the cause of a fault condition. Other operational characteristics of the part, such as DAC output currents, U GPIO modes, and tachometer frequency, are also pro- APPLICATIO S grammed through the serial interface. Two address pins n Servers provide nine possible device addresses. n Desktop Computers n The BLAST pin is provided to force the DAC output Power Supplies n currents to program the maximum regulator output Cooling Systems voltages through a single pin and gate the operation of the , LTC and LT are registered trademarks of Linear Technology Corporation. 2 I C is a trademark of Philips Electronics N.V. serial access timer. TYPICAL APPLICATIO Low Parts Count, High Efficiency Dual Fan Control 3.3V 12V + 3.3V 0.1F 10F + R C SENSE1 VIN1 10k V 3.3V CC V IN 0.05 22F RUN/SS SENSE FAULT GPI04 DC R FB1A 10k LTC1771 FAN TO 75k SYSTEM + SDA BLAST I PGATE MASTER TH Si6447DQ C RESET OUT1 TACH R L1 47H 150F C1 R SCL IDACOUTA V MODE FB1B OUT 10k FB 28k C C C1 FB1 GND UPS5817 220pF 100pF LTC1840 12V 2-NMB 6820PL-04W-B29-D50 FANS 3.3V + 1.1A NOM AT 12V R C VIN2 SENSE2 3.3V V IN 0.05 22F 3.3V RUN/SS SENSE 130 NC A0 GPI03 DC R FB2A 10k LTC1771 FAN 75k + I PGATE NC A1 IDACOUTB Si6447DQ 130 TH C OUT2 LED1 L2 47H TACH R 150F C2 R GPI01 TACHB 10k V MODE FB2B OUT FB LED2 28k C C C2 FB2 GND UPS5817 220pF 100pF GPI02 TACHA GND ADDRESS = 1110010 (8 OTHERS POSSIBLE) 1840 TA01 1840f 1 U ULTC1840 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART V to GND .................................................... 0.3 to 6V TOP VIEW CC NUMBER A0, A1 ............................................. 0.3 to (V + 0.3V) SCL 1 16 V CC CC I , I ............................. 0.3 to (V + 0.75V) LTC1840CGN SDA 2 15 I DACOUTA DACOUTB CC DACOUTA All other pins ................................................. 0.3 to 6V A1 3 14 I LTC1840IGN DACOUTB A0 4 13 BLAST Operating Temperature FAULT 5 12 TACHB LTC1840C ............................................... 0 C to 70 C GPIO1 6 11 TACHA LTC1840I.............................................40 C to 85 C GN PART GPIO2 7 10 GPIO4 Storage Temperature Range ..................65 C to 125 C MARKING GND 8 9 GPIO3 Lead Temperature (Soldering, 10 sec).................. 300 C 1840 GN PACKAGE 16-LEAD PLASTIC SSOP 1840I T = 125 C, q = 110 C/W JMAX JA Consult LTC marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 3V A CC SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS DACs n Resolution 8 Bits DNL Differential Nonlinearity V = 1.1V, Guaranteed Monotonic l 0.9 LSB DACOUT INL Integral Nonlinearity V = 1.1V 4LSB DACOUT ZSE Zero-Scale Error V = 1.1V 0.2 0.1 2 m A DACOUT Output Voltage Rejection 1.1V< V < 3.75V 1LSB DACOUT Output Voltage Rejection V = 5.75V, 1.1V < V < 6.5V 2LSB CC DACOUT I Full-Scale Current Sinking 97 103 m A DACOUTA(FS), I V = 1.1V l 95 105 m A DACOUTB(FS) DACOUT Power Supply V Positive Supply Voltage l 2.7 5.75 V CC I Supply Current V = 3V, A0 and A1 Floating 400 600 m A CC CC V = 5V, A0 and A1 Floating 500 750 m A CC V UVLO/POR Voltage l 2.1 2.4 2.69 V UVLO V UVLO/POR Voltage Hysteresis (Note 2) 20 90 160 mV UVHYS Oscillator Performance f Oscillator Frequency l 47 50 53 kHz OSC PSRR Supply Sensitivity 2.7V < V < 5.75V 0.1 0.5 %/V CC GPIO Performance I Output Current Sink V = 0.7V, Internal Pull-Down Enabled l 10 mA O GPIOX V Digital Input Low Voltage Internal Pull-Down Disabled l 0.3V V IL CC V Digital Input High Voltage Internal Pull-Down Disabled l 0.7V V IH CC V Input Hysteresis (Note 2) 50 mV IHYST I Leakage Internal Pull-Down Disabled 1 m A LEAK 1840f 2 U WWW