MIC2591B Micrel MIC2591B Dual-Slot PCI Express Hot-Plug Controller General Description Features The MIC2591B is a dual-slot power controller supporting the power distribution requirements for Peripheral Component Interconnect Express (PCI Express) Hot-Plug compliant systems incorporating the Intelligent Platform Management Interface (IPMI) Specification v1.0. The MIC2591B provides complete power control support for two PCI Express slots, including the 3.3VAUX defined by the PCI Express standards. Support for 12V, 3.3V, and 3.3VAUX supplies is provided including programmable constant-current inrush limiting, voltage supervision, programmable current limit, and circuit breaker functions. These features provide comprehensive system protection and fault isolation. The MIC2591B also incorporates an SMBus interface via which complete status of each slot is provided. Data such as voltage and current from each supply of each slot can be obtained for IPMI sensor records in addition to the power status of each slot. All support documentation can be found on Micrel's web site at www.micrel.com. * Supports two independent PCI Express slots * SMBus interface for slot power control and status * Voltage-tolerant I/O for compatibility with SMBus 2.0 systems * 12V, 3.3V, and 3.3VAUX supplies supported per PCI Express Specification v1.0a * On-chip circuitry for data collection of each rail output voltage and output current for both slots - Integral analog multiplexer and 8-bit ADC - Compliant to the Intelligent Platform Management Interface (IPMI) Specification v1.0 - Conversion results available via an SMBus interface * Programmable inrush current limiting * Active current regulation controls inrush current * Electronic circuit breaker for each supply to each slot * High accuracies for both circuit breaker trip points and nuisance trip prevention timers * Dual level fault detection for quick fault response without nuisance tripping * Thermal isolation between circuitry for Slot A and Slot B * Two General Purpose Input pins suitable for interface to logic and switches. Applications * PCI Express v1.0a hot-plug power control Ordering Information Part Number Standard Pb-Free MIC2591B - 2BTQ 12V and 3V Fast-Trip Thresholds MIC2591B - 2YTQ 3.3VAUX Current Limit Package 100mV 0.375A 48 Pin TQFP MIC2591B - 3BTQ* MIC2591B - 3YTQ* 150mV 0.375A 48 Pin TQFP MIC2591B - 5BTQ* MIC2591B - 5YTQ* Disabled 0.375A 48 Pin TQFP * Contact factory for availability Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com August 2004 1 M9999-082004 MIC2591B Micrel Typical Application +12V System Power +3.3V Supply VSTBY 0.1F 11 33 23.2k 1% 20 PCI Express Connector 0.1F 26 VSTBYA VSTBYB IREF VAUXA RFILTER[A&B] 12VINA 110k 1% 12VSENSEA VSTBY C1 2 CFILTERA 35 CFILTERB 100k 100k 5 3 *R12VGATEA 15 Si4435DY CMILLER 6800pF 100k 9 /FORCE_ONA /FORCE_ONA 12VOUTA 10 3VINA 12 /FORCE_ONB 12V 2.1A (x4/x8) 0.1F 28 RSENSE 0.013 /FORCE_ONB 4 GPI_A0 38 GPI_B0 GPI_A0 3VSENSEA 13 3VGATEA 14 GPI_B0 VSTBY 3VOUTA 45 AUXENA AUXENB ONA 42 44 43 ONB 32 12VSENSEB 29 CGS 22nF ONB 12VGATEB 34 *R12VGATEB 15 Si4435DY # CMILLER 6800pF 27 10k x 4 12V 2.1A (x4/x8) 0.1F 6 31 1 36 41 40 39 37 VSTBY RSENSE 0.020 # 12VOUTB SMBus Base Address 3.3V 3.0A 0.1F AUXENA AUXENB ONA Hot-Plug Controller /FAULTB Si4420DY 15 CGATE 22nF 12VINB VSTBY /PWRGDA /PWRGDB /FAULTA *R3VGATEA 16 # MIC2591B 10k x 4 3.3AUX 375mA RSENSE 0.020 8 # C2 100k 0.1F # CGS 22nF 12VGATEA PCI Express Bus 15 /PWRGDA /PWRGDB /FAULTA /FAULTB 3VINB 3VSENSEB 24 3VGATEB 23 A0 A1 A2 /INT 47 SCL 48 SDA 3VOUTB 21 VAUXB 22 GND GND RSENSE 0.013 25 17 *R3VGATEB Si4420DY 15 3.3V 3.0A # CGATE 22nF 3.3AUX 375mA 46 PCI Express Bus 10k x 3 SMBus I/O SDA SDA SCL SCL /INT /INT PCI Express Connector Management Controller * Values for R12VGATE[A/B] and R3VGATE[A/B] may vary # depending upon the CGS of the external MOSFETs. These components are not required for MIC2591B operation but can be implemented for GATE output slew rate control (application specific) * Bold lines indicate high current paths August 2004 2 M9999-082004 MIC2591B Micrel Pin Configuration SDA SCL GND AUXENA ONA ONB AUXENB A0 A1 A2 GPI_B0 /INT Hot-Plug Control Interface 48 47 46 45 44 43 42 41 40 39 38 37 /FAULTA CFILTERA 12VGATEA GPI_A0 12VINA /PWRGDA NC 12VSENSEA /FORCE_ONA 12VOUTA VSTBYA 3VINA 36 35 34 33 32 31 30 29 28 27 26 25 1 2 3 4 5 6 7 8 9 10 11 12 /FAULTB CFILTERB 12VGATEB IREF 12VINB /PWRGDB NC 12VSENSEB /FORCE_ONB 12VOUTB VSTBYB 3VINB Slot A Interface 3VSENSEA 3VGATEA VAUXA 3VOUTA GND NC NC RFILTER[A&B] 3VOUTB VAUXB 3VGATEB 3VSENSEB 13 14 15 16 17 18 19 20 21 22 23 24 Slot B Interface 48-Pin TQFP August 2004 3 M9999-082004 MIC2591B Micrel Pin Description Pin Number Pin Name 5 32 12VINA 12VINB 12V Supply Power and Sense Inputs: Two pins are provided for Kelvin connection (one for each slot). Pin 5 is the (+) Kelvin-sense connection to the supply side of the sense resistor for 12V Slot A. Pin 32 is the (+) Kelvinsense connection to the supply side of the sense resistor for 12V Slot B. These two pins must ultimately connect to each other as close as possible at the MIC2591B controller in order to eliminate any IR drop between these pins. An undervoltage lockout circuit (UVLO) prevents the switches from turning on while this input is less than its lockout threshold. 12 25 3VINA 3VINB 3.3V Supply Power and Sense Inputs: Two pins are provided for connection (one for each slot). Pin 12 is the (+) Kelvin-sense connection to the supply side of the sense resistor for 3V Slot A. Pin 25 is the (+) Kelvinsense connection to the supply side of the sense resistor for 3V Slot B. These two pins must ultimately connect to each other as close as possible at the MIC2591B controller in order to eliminate any IR drop between these pins. An undervoltage lockout circuit (UVLO) prevents the switches from turning on while this input is less than its lockout threshold. 16 21 3VOUTA 3VOUTB 3.3V Power-Good Sense Inputs: Connect to 3.3V[A/B] outputs (i.e., the source terminal of the external power MOSFET). Used to monitor the 3.3V output voltages for Power-is-Good status. 10 27 12VOUTA 12VOUTB 12V Power-Good Sense Inputs: Connect to 12V[A/B] outputs (i.e., the drain terminal of the external power MOSFET). Used to monitor the12V output voltages for Power-is-Good status. 8 29 12VSENSEA 12VSENSEB 12V Circuit Breaker Sense Inputs: The current limit thresholds are set by connecting sense resistors between these pins and 12VIN[A/B]. When the current limit threshold of IR = 50mV is reached, the 12VGATE[A/B] pin is modulated to maintain a constant voltage across the sense resistor and therefore a constant current into the load. If the 50mV threshold is exceeded for tFLT, the circuit breaker is tripped and the GATE pin for the affected supply's external MOSFET is immediately pulled high. 13 24 3VSENSEA 3VSENSEB 3V Circuit Breaker Sense Inputs: The current limit thresholds are set by connecting sense resistors between these pins and 3VIN[A/B]. When the current limit threshold of IR = 50mV is reached, the 3VGATE[A/B] pin is modulated to maintain a constant voltage across the sense resistor and therefore a constant current into the load. If the 50mV threshold is exceeded for tFLT, the circuit breaker is tripped and the GATE pin for the affected supply's external MOSFET is immediately pulled low. 3 34 12VGATEA 12VGATEB 12V Gate Drive Outputs: Each pin connects to the gate of an external P-Channel MOSFET. During power-up, the CGATE and the CGS of the MOSFETs are connected to a 25A current sink. This controls the value of dv/dt seen at the source of the MOSFETs. During current limit events, the voltage at this pin is adjusted to maintain constant current through the switch for a period of tFLT. Whenever an overcurrent, thermal shutdown, or input undervoltage fault condition occurs, the GATE pin for the affected slot is immediately brought high. These pins are charged by an internal current source during power-down. 14 23 3VGATEA 3VGATEB 3V Gate Drive Outputs: Each pin connects to the gate of an external N-Channel MOSFET. During power-up, the CGATE and the CGS of the MOSFETs are connected to a 25A current source. This controls the value of dv/dt seen at the source of the MOSFETs, and hence the current flowing into the load capacitance. During current limit events, the voltage at this pin is adjusted to maintain constant current through the switch for a period of tFLT. Whenever an overcurrent, thermal shutdown, or input undervoltage fault condition occurs, the GATE pin for the affected slot is immediately brought low. During powerdown, these pins are discharged by an internal current source. 33 August 2004 IREF Pin Function A resistor connected between this pin and GND sets the ADC current measurement gain for the VAUX[A/B] outputs. This resistor must be 23.2k1%. 4 M9999-082004 MIC2591B Micrel Pin Description (continued) Pin Number Pin Name 11 26 VSTBYA VSTBYB 3.3V Standby Input Voltage: Required to support PCI Express VAUX output. Additionally, the SMBus logic and internal registers run off of VSTBY[A/B] to ensure that the chip is accessible during standby modes. A UVLO circuit prevents turn-on of this supply until VSTBY[A/B] rises above its UVLO threshold. Both pins must be connected together at the MIC2591B controller. 15 22 VAUXA VAUXB 3.3VAUX Outputs to PCI Express Card Slots: These outputs connect the 3.3AUX pin of the PCI Express connectors to VSTBY[A/B] via internal 400m MOSFETs. These outputs are current limited and protected against short-circuit faults. 44 43 ONA ONB Enable Inputs: Rising-edge triggered. Used to enable or disable the MAINA and MAINB (+3.3V and +12V) outputs. Taking ON[A/B] low after a fault resets the +12V and/or +3.3V fault latches for the affected slot. Tie these pins to GND if using SMI power control. Also, see pin description for /FAULTA and /FAULTB. 45 42 AUXENA AUXENB Enable Inputs: Rising-edge triggered. Used to enable or disable the VAUX[A/B] outputs. Taking AUXEN[A/B] low after a fault resets the respective slot's Aux Output Fault Latch. Tie these pins to GND if using SMI power control. Also, see pin description for /FAULTA and /FAULTB. 2 35 CFILTERA CFILTERB Overcurrent Timers: Capacitors connected between these pins and GND set the duration of tFLT. tFLT is the amount of time for which a slot remains in current limit before its circuit breaker is tripped. 6 31 /PWRGDA /PWRGDB Power-is-Good Outputs: Open-drain, active-low. Asserted when a slot has been commanded to turn on and has successfully begun delivering power to its respective +12V, +3.3V, and VAUX outputs. Each pin requires an external pull-up resistor to VSTBY. 1 36 /FAULTA /FAULTB Fault Outputs: Open-drain, active-low. Asserted whenever the circuit breaker trips due to a fault condition (overcurrent, input undervoltage, overtemperature). Each pin requires an external pull-up resistor to VSTBY. Bringing the slot's ON[A/B] pin low resets /FAULT[A/B] if /FAULT[A/B] was asserted in response to a fault condition on one of the slot's MAIN outputs (+12V or +3.3V). /FAULT[A/B] is reset by bringing the slot's AUXEN[A/B] pin low if /FAULT[A/B] was asserted in response to a fault condition on the slot's VAUX output. If a fault condition occurred on both the MAIN and VAUX outputs of the same slot, then both ON[A/B] and AUXEN[A/B] must be brought low to deassert the /FAULT[A/B] output. 9 28 /FORCE_ONA /FORCE_ONB Enable Inputs: Active-low, level-sensitive. Asserting a /FORCE_ON[A/B] input will turn on all three of the respective slot's outputs (+12V, +3.3V, and VAUX), while specifically defeating all protections on those supplies. This explcitly includes all overcurrent and short circuit protections, and on-chip thermal protection for the VAUX[A/B] supplies. Additionally included are the UVLO protections for the +3.3V and +12V main supplies. The /FORCE_ON[A/B] pins do not disable UVLO protection for the VAUX[A/B] supplies. These input pins are intended for diagnostic purposes only. Asserting /FORCE_ON[A/B] will cause the respective slot's /PWRGD[A/B] and /FAULT[A/B] pins to enter their open-drain state. Note that the SMBus register set will continue to reflect the actual state of each slot's supplies. There is a pair of register bits, accessible via the SMBus, which can be set to disable (unconditionally deassert) either or both of the /FORCE_ON[A/B] pins -- See CNTRL[A/B] Register Bit D[2]. 4 38 GPI_A0 GPI_B0 August 2004 Pin Function General Purpose Inputs: The states of these two inputs are available by reading the Common Status Register, Bits [4:5]. If not used, connect each pin to GND. 5 M9999-082004 MIC2591B Micrel Pin Description (continued) Pin Number Pin Name 39 40 41 A2 A1 A0 48 SDA SMBus Data: Bidirectional SMBus data line. 47 SCL SMBus Clock: Input. 37 /INT Interrupt Output: Open-drain, active-low. Asserted whenever a power fault is detected if the INTMSK bit (CS Register Bit D[3]) is a logical "0". This output is cleared by performing an "echo reset" to the appropriate fault bit(s) in the STAT[A/B] and/or CS registers. This pin requires an external pull-up resistor to VSTBY. 17 46 GND 2 Pins, IC Ground Connections: Tie directly to the system's analog GND plane directly at the device. 20 RFILTER[A&B] 7 18 19 30 NC August 2004 Pin Function SMBus Address Select Pins: Connect to ground or leave open in order to program device SMBus base address. These inputs have internal pull-up resistors to VSTBY[A/B]. Connecting this pin to GND through a 110k, 1% resistor will provide a significant improvement in timeout duration accuracy for slow overcurrent faults on Slot A and Slot B. If left floating (NC), overcurrent timeout duration accuracy is determined by the specification for VFILTER and IFILTER. Please see the "Circuit Breaker Function" text in the "Functional Description" section for more detail. Reserved: Make no external connections to these pins. 6 M9999-082004 MIC2591B Micrel Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltages 12VIN[A/B] ................................................................................ 14V 3VIN[A/B], VSTBY[A/B] ............................................... 7V Any Logic Pin ........................ -0.5V (min) to 3.6V (max) Output Current (/FAULT[A/B], /INT, SDA) .................. 10mA Power Dissipation .................................... Internally Limited Lead Temperature (IR Reflow, Peak Temperature) .......... 240C +0C/-5C Storage Temperature ............................... -65C to +150C ESD Rating(3) Human Body Model ................................................... 2kV Machine Model ........................................................ 200V Supply Voltages 12VIN[A/B] .............................................. 11.0V to 13.0V 3VIN[A/B] .................................................... 3.0V to 3.6V VSTBY[A/B] ................................................. 3.0V to 3.6V Ambient Temperature (TA) ............................ 0C to + 70C Junction Temperature (TJ) ........................................ 125C Package Thermal Resistance TQFP (JA) ....................................................... 56.5C/W Electrical Characteristics(4) 12VIN[A/B] = 12V, 3VIN[A/B] = 3.3V, VSTBY[A/B] = 3.3V, TA = 25C, unless otherwise noted. Bold indicates specification applies over the full operating temperature range from 0C to +70C. Symbol Parameter Condition Min Typ Max Units 2.5 0.5 2.5 5 1 5 mA mA mA 9 2.5 2.9 10 2.75 3.0 V V V Power Control and Logic Sections ICC12 ICC3.3 ICCSTBY VUVLO(12V) VUVLO(3V) VUVLO(STBY) Supply Current Undervoltage Lockout Thresholds 12VIN[A/B] 3VIN[A/B] VSTBY[A/B] 12VIN[A/B] increasing 3VIN[A/B] increasing VSTBY[A/B] increasing 8 2.2 2.8 VHYSUV Undervoltage Lockout Hysteresis 12VIN, 3VIN 180 mV VHYSSTBY Undervoltage Lockout Hysteresis VSTBY[A/B] 50 mV VUVTH(12V) VUVTH(3V) VUVTH(VAUX) Power-Good Undervoltage Thresholds 12VOUT[A/B] 3VOUT[A/B] VAUX[A/B] VHYSPG Power-Good Detect Hysteresis VGATE(12V) 12VGATE Voltage 12VOUT[A/B] decreasing 3VOUT[A/B] decreasing VAUX[A/B] decreasing 10.2 2.7 2.7 10.5 2.8 2.8 10.8 2.9 2.9 30 0 IGATE(12VSINK) 12VGATE Sink Current Start Cycle 15 IGATE(12VPULLUP) 12VGATE Pull-up Current (Fault Off) Any fault condition (VDD -VGATE) = 2.5V VGATE(3V) 3VGATE Voltage 25 mV 1.5 V 35 A -20 mA 12VIN-1.5 IGATE(3VCHARGE) 3VGATE Charge Current Start Cycle 15 IGATE(3VSINK) 3VGATE Sink Current (Fault Off) Any fault condition VGATE = 2.5V 40 V V V 25 12VIN V 35 A mA CFILTER[A/B] Overcurrent Delay Time, Pin 20 (RFILTER[A&B]) Floating or NC VFILTER CFILTER[A/B] Threshold Voltage IFILTER CFILTER[A/B] Charging Current Delay(ms) = CFILTER (F) x VFILTER (V) IFILTER (A ) x 10 3 V12VIN - V12VSENSE > VTHILIMIT and/or V3VIN - V3VSENSE > VTHILIMIT 1.20 1.25 1.30 V 1.80 2.5 5.0 A Notes: 1. Exceeding measurements given within the "Absolute Maximum Ratings" section may damage the device. 2. The device is not guaranteed to function outside of the measurements given in the "Operating Ratings" section. 3. Devices are ESD sensitive. Employ proper handling precautions. The human body model is 1.5k in series with 100pF. 4. Specification for packaged product only. August 2004 7 M9999-082004 MIC2591B Micrel Electrical Characteristics (continued)(5) Symbol Parameter Condition Min Typ Max Units 4.4 5 5.6 45 45 50 50 55 55 mV mV 90 135 100 150 Disabled 110 165 mV mV CFILTER Overcurrent DelayTime, Pin 20 grounded through RFILTER[A&B] = 110 k, 1% SF CFILTER Overcurrent Delay Scaling Factor Delay(ms) = CFILTER(F) x RFILTER(k) x SF VTHILIMIT V12VIN - V12VSENSE > VTHILIMIT and/or V3VIN -V3VSENSE > VTHILIMIT Current Limit Threshold Voltages 12V[A/B] supplies 3.3V[A/B] supplies V3VIN - V3VSENSE VTHFAST 12VOUT[A/B] and 3VOUT[A/B] Fast-Trip Threshold Voltages V12VIN - V12VSENSE V3VIN - V3VSENSE I12VSENSE[A/B] 12VSENSE[A/B] Input current 0.35 A I3VSENSE[A/B] 3VSENSE[A/B] Input current 0.35 A VIL LOW-Level Input Voltage ON[A/B], AUXEN[A/B], GPI_[A0/B0], /FORCE_ON[A/B] VOL Output LOW Voltage /FAULT[A/B], /PWRGD[A/B], /INT, SDA VIH HIGH-Level Input Voltage ON[A/B], AUXEN[A/B], GPI_[A0/B0], /FORCE_ON[A/B], A[0-2], SCL, SDA V12VIN - V12VSENSE MIC2591B-2BTQ MIC2591B-3BTQ MIC2591B-5BTQ -0.5 IOL = 3mA 2.1 RPULLUP(A0 - A2) Internal Pull-ups from A[0-2] to VSTBY[A/B] 0.8 V 0.4 V 3.6 V 40 k ILKG,OFF(12VIN[A/B]) 12VIN[A/B] Input leakage current VSTBY = VSTBY[A/B] = +3.3V, 12VIN[A/B] = OFF; 3VIN[A/B] = OFF 1 A ILKG,OFF(3VIN[A/B]) 3VIN[A/B] Input leakage current VSTBY = VSTBY[A/B] = +3.3V, 3VIN[A/B] = OFF; 12VIN[A/B] = OFF 1 A 5 A 5 A IIL Input Leakage Current SCL, ON[A/B], AUXEN[A/B], /FORCE_ON[A/B] ILKG(OFF) Off-State Leakage Current /FAULT[A/B], /PWRGD[A/B], /INT, SDA, GPI_[A0/B0] GPI_[A0/B0]: ILKG for these two pins measured with VAUX OFF TOV Overtemperature Shutdown and Reset Thresholds, with overcurrent on slot TJ increasing, each slot(6) TJ decreasing, each slot(6) 140 130 C C Overtemperature Shutdown and Reset Thresholds, all other conditions (all outputs will latch OFF) TJ increasing, both slots(6) TJ decreasing, both slots(6) 160 150 C C RDS(AUX) Output MOSFET Resistance VAUX[A/B] MOSFET IDS = 375mA, TJ = 125C 400 m VOFF(VAUX) Off-State Output Offset Voltage VAUX[A/B] VAUX[A/B] = Off, TJ = 125C 50 mV Notes: 5. Specification for packaged product only. 6. Parameters guaranteed by design. Not 100% production tested. August 2004 8 M9999-082004 MIC2591B Micrel Electrical Characteristics (continued)(7) Symbol Parameter Condition Min IAUX(THRESH) Auxiliary Output Current Limit Threshold (Figure 4) Current which must be drawn from VAUX to register as a fault ISC(TRAN) Maximum Transient Short Circuit Current VAUX Enabled, then Grounded ILIM(AUX) Regulated Current after Transient From end of ISC(TRAN) to CFILTER time-out RDIS(12V) RDIS(3V) RDIS(VAUX) Output Discharge Resistance 12VOUT[A/B] 3VOUT[A/B] 3VAUX[A/B] 12VOUT[A/B] = 6.0V 3VOUT[A/B] = 1.65V 3VAUX[A/B] = 1.65V Typ Max 0.84 IMAX = 0.375 Units A VSTBY[A /B] RDS(AUX) 0.7 1.35 1600 150 430 A A tOFF(12V) 12V Current Limit Response Time (Figure 2) MIC2591B-2BTQ CGATE = 25pF VIN -VSENSE = 140mV 1 2.0 s tOFF(3V) 3.3V Current Limit Response Time (Figure 3) MIC2591B-2BTQ CGATE = 25pF VIN -VSENSE = 140mV(8) 1 2.0 s tSC(TRAN) VAUX[A/B] Current Limit Response Time (Figure 5) VAUX[A/B] = 0V, VSTBYA = VSTBYB = +3.3V 2.5 5 s tPROP(12VFAULT) Delay from 12V[A/B] Overcurrent Limit to /FAULT output MIC2591B-2BTQ CFILTER = 0 VIN -VSENSE = 140mV(8) 1 s tPROP(3VFAULT) Delay from 3V[A/B] Overcurrent Limit to /FAULT[A/B] Output MIC2591B-2BTQ CFILTER = 0 VIN -VSENSE = 140mV(8) 1 s tPROP(VAUXFAULT) Delay from VAUX[A/B] Overcurrent MIC2591B-2BTQ limit to /FAULT[A/B] output CFILTER = 0 VAUX Output Grounded(8) 1 s tW ON[A/B], AUXEN[A/B] Pulse Width Note 8 100 ns tPOR MIC2591B Power-On Reset Time after VSTBY[A/B] becomes valid Note 8 250 s SMBus Timing t1 SCL (clock) period Figure 1 2.5 s t2 Data In setup time to SCL HIGH Figure 1 100 ns t3 Data Out stable after SCL LOW Figure 1 300 ns t4 Data LOW setup time to SCL LOW Start condition, Figure 1 100 ns t5 Data HIGH hold time after SCL HIGH Stop condition, Figure 1 100 ns Notes: 7. Specification for packaged product only. 8. Parameters guaranteed by design. Not 100% production tested. August 2004 9 M9999-082004 MIC2591B Micrel Electrical Characteristics (continued)(9) Symbol Parameter Condition Min Typ Max Units -5 +5 % F.S. -5 +5 % F.S. 8-Bit Analog to Digital Converter Max_Error Total unadjusted error for: Voltage, All Outputs tCONV Current, 3VOUT[A/B] and 12VOUT[A/B] Measured as voltage across corresponding external RSENSE Current, VAUX[A/B] 23.2k resistor from IREF (Pin 33) to GND Conversion time % F.S. 5 60 100 ms Resolution Specifications VAUXA Full Scale Voltage 4.00 VAUXB LSB of Voltage V 15.62 mV Full Scale Current 375 mA LSB of Current 1.47 mA 3.85 V x4/x8 Values 3VOUTA Full Scale Voltage 3VOUTB LSB of Voltage 15.0 mV Full Scale Current 4.23 A LSB of Current 16.5 mA External RSENSE = 13.0m 12VOUTA Full Scale Voltage 13.8 V 12VOUTB LSB of Voltage 53.9 mV Full Scale Current 2.75 A LSB of Current 10.7 mA 3.85 V External RSENSE = 20.0m x16 Values 3VOUTA Full Scale Voltage 3VOUTB LSB of Voltage 15.0 mV Full Scale Current 4.23 A LSB of Current 16.5 mA 12VOUTA Full Scale Voltage 12VOUTB LSB of Voltage External RSENSE = 13.0m External RSENSE = 10.0m 13.8 V 53.9 mV Full Scale Current 5.5 A LSB of Current 21.5 mA Notes: 9. Specification for packaged product only. August 2004 10 M9999-082004 MIC2591B Micrel Timing Diagrams t1 SCL t4 t2 t5 SDA Data In t3 SDA Data Out Figure 1. SMBus Timing VIN - VSENSE VIN - VSENSE VTHFAST VTHFAST VTHILIMIT VTHILIMIT 3VGATE 6V 12VGATE OV tOFF(12V) 1V OV t t tOFF(3V) Figure 2. 12V Current Limit Response Timing Figure 3. 3V Current Limit Response Timing ISC(TRAN) IAUX(THRESH) Must Trip May Not Trip I I ILIM(AUX) IOUT(AUX) ILIM(AUX) IOUT(AUX) IOUT(AUX) tSC(TRAN) O O t Figure 5. VAUX Current Limit Response Timing Figure 4. VAUX Current Limit Threshold August 2004 t 11 M9999-082004 MIC2591B Micrel Function Block Diagram ON[A/B] AUX[A/B] VSTBY[A/B] 12VIN[A/B] Power-on Reset 250s VSTBY UVLO 12VGATE[A/B] VAUX Charge Pump & MOSFET Bandgap Reference VAUX[A/B] 12VSENSE[A/B] 50mV VREF VAUX Overcurrent 12VIN[A/B] 3VIN[A/B] 12V UVLO 3VGATE[A/B] ON/OFF 3VSENSE[A/B] 50mV 12VBIAS 3VIN[A/B] ON/OFF /PWRGD[A/B] 100mV* ON/OFF Thermal Shutdown ON/OFF 100mV* /FAULT[A/B] 3V UVLO ON/OFF Overcurrent Detection VAUX PWRGD VSTBY(REF) IREF 3VPWRGD 3VOUT[A/B] Logic Circuits Current Mirror VREF 12VPWRGD 12VOUT[A/B] CFILTER[A/B] VREF /INT VREF RFILTER[A&B] RFILTER[A&B] OPEN PIN DETECTOR MUX & 12 Channel, 8-bit A/D Converter /FORCE_ON[A/B] VAUX FULL-SCALE CURRENT REFERENCE GND IREF VSTBY(REF) DIGITAL CORE/SERIAL INTERFACE 40k x 3 GPI_[A0/B0] * MIC2591B-3BTQ fast threshold is 150mV MIC2591B-5BTQ fast threshold is disabled Contact factory for availabilty SCL SDA A2 A1 A0 MIC2591B Block Diagram August 2004 12 M9999-082004 MIC2591B Micrel as shown below in Figure 6 (Disabling HPI when SMI control is used). This configuration safeguards the power slots in the event that the SMBus communication link is disconnected for any reason. Additionally, when utilizing the HPI exclusively, the SMBus (or SMI) will be inactive if the input pins (SDA, SCL, A0, A1, and A2) are configured as shown in Figure 6 below (Disabling SMI when HPI Control is used). Power-On Reset and Power Cycling The MIC2591B utilizes VSTBY[A/B] as the main supply input source. VSTBY[A/B] is required for proper operation of the MIC2591B's SMBus and registers and must be applied at all times. A Power-On Reset (POR) cycle is initiated after VSTBY[A/B] rises above its UVLO threshold and remains valid at that voltage for 250s. All internal registers are cleared after POR. If VSTBY[A/B] is recycled, the MIC2591B enters a new power-on-reset cycle. VSTBY must be the first supply input applied followed by the MAIN supply inputs of 12VIN and 3VIN. The SMBus is ready for access at the end of the POR cycle (250s after VSTBY[A/B] is valid). During tPOR, all outputs remain off. In most applications, the total POR interval will consist of the time required to charge the VSTBY input (bypass) capacitance to the UVLO threshold plus the internal tPOR. The following equation is used to approximate the total POR interval: Functional Description Hot Swap Insertion When circuit boards are inserted into systems carrying live supply voltages ("hot-plugged"), high inrush currents often result due to the charging of bulk capacitance that resides across the circuit board's supply pins. This transient inrush current can cause the system's supply voltages to temporarily go out of regulation, causing data loss or system lock-up. In more extreme cases, the transients occurring during a hot-plug event may cause permanent damage to connectors or on-board components. The MIC2591B addresses these issues by limiting the inrush currents to the load (PCI Express Board), and thereby controlling the rate at which the load's circuits turn-on. In addition to this inrush current control, the MIC2591B offers input and output voltage supervisory functions and current limiting to provide robust protection for both the system and circuit board. System Interface The MIC2591B employs two system interfaces: the hardware Hot-Plug Interface (HPI) and the System Management Interface (SMI). The HPI includes ON[A/B], AUXEN[A/B], as well as /FAULT[A/B]; the SMI consists of SDA, SCL, and /INT, whose signals conform to the levels and timing of the SMBus specification. The MIC2591B can be operated exclusively from the SMI, or can employ the HPl for power control while continuing to use the SMI for access to all but the power control registers. In addition to the basic power control features of the MIC2591B accessible by the HPI, the SMI also gives the host access to the following information from the part: * Output voltage and current from each supply. * Fault conditions occurring on each supply. * GPI_[A0/B0] pin status. When using the System Management Interface for power control, do not use the Hot-Plug Interface. Conversely, when using the Hot-Plug Interface for power control, do not execute power control commands over the System Management Interface bus (all other register accesses via the SMI bus remain permissible while in the HPI control mode). When utilizing the SMI exclusively, the HPI input pins (ON[A/B], AUXEN[A/B], and /FORCE_ON[A/B] should be configured ( C STBY (F) x VULVO(STBY) tPOR_TOTAL (S) = ICHARGE(STBY) (A) 100k + tPOR (S) Enabling the GATE output When a slot's MAIN supplies are off, the 12VGATE pin is held high with an internal pull-up. Similarly, the 3VGATE pin is internally held low. When the MAIN supplies of the MIC2591B are enabled by asserting ON[A/B], the 3VGATE[A/B] and 12VGATE[A/B] pins are each connected to a constant current supply. These supplies are each nominally 25A. For a slot's 3VGATE pin, this is a current source; for the 12VGATE pin, this is a current sink. VSTBY MIC2591B 100k 47 48 /INT -6 where CSTBY is the VSTBY input bulk bypass capacitance and ICHARGE(STBY) is the current supplied by the VSTBY source to charge the capacitance. Power-Up Cycle VSTBY 100k ) x 10 37 39 40 41 100k SCL SDA /INT A2 A1 A0 100k 9 28 45 42 44 43 Disabling SMI when HPI Control is used MIC2591B /FORCE_ONA /FORCE_ONB AUXENA AUXENB ONA ONB Disabling HPI when SMI Control is used Figure 6. Input Pin Configuration for Disabling HPI/SMI Control August 2004 13 M9999-082004 MIC2591B Micrel Inrush Current and Load Dominated Start-up The expected maximum inrush current can be calculated by using the following equation: INRUSH IGATE x CLOAD C GATE 25A x t12VDLY CLOAD C GATE ILIM(3V /12V ) 0.047F 0.1F CLOAD(3V /12V ) Consequently, the overcurrent timer delay must be programmed to exceed the time it will take to charge the output load to the input rail voltage level. * MAIN Outputs (Start-up Delay and Slew-Rate Control) (C GATE x VGS(TH) ) The source (output) side of the external MOSFET will reach the drain voltage in a time given by: (C LOAD x VDRAIN ) ILIM(3V) For the 12V outputs, each MOSFET is configured as a Miller integrator (by virtue of CMILLER, which is connected between the MOSFET's gate and drain). In this configuration, the feedback action from drain to gate of the MOSFET causes the voltage at the drain of the MOSFET to slew in a linear fashion at a rate which satisfies the following equation: I dv / dt(12V) = - GATE CMILLER A delay exists between the ON command to a slot and the appearance of voltage at the slot's 12V output. For a slot's 12V output, that delay is given by the time required for the capacitor from the gate of the MOSFET to its source (typically five times the value of CMILLER) to charge to the threshold voltage of the MOSFET (typically about 3V). In this instance, the delay before the output voltage starts ramping can be approximated by: August 2004 ) IGATE 0.532 V/ms 0.250V/ms Values in this range will be affected by the internal parasitic capacitances of the MOSFETs used, and should be verified experimentally. Power-Down Cycle When a slot is turned off, resistors internal to the MIC2591B are connected to each of the outputs to provide a discharge path for capacitors connected to the part's outputs. The nominal output discharge resistance values for each rail are found in the "Electrical Characteristics" table. Standby Mode Standby mode is entered when one or more of the MAIN supply inputs (12VIN and/or 3VIN) is below its respective UVLO threshold or OFF. The MIC2591B also supplies 3.3V auxiliary outputs (VAUX[A/B]), satisfying PCI Express specifications. These outputs are fed via the VSTBY[A/B] input pins and controlled by the AUXEN[A/B] input pins or via their respective bits in the Control Registers. These outputs are independent of the MAIN outputs (12VIN[A/B] and 3VIN[A/B]). Should the MAIN supply inputs move below their respective UVLO thresholds, VAUX[A/B] will still function as long as VSTBY[A/B] is present. Prior to standby mode, ONA and ONB (or the Control Registers' MAINA and MAINB bits) inputs should be deasserted or the MIC2591B will assert /FAULT[A/B] and /INT (if interrupts are enabled) output signals, if an undervoltage condition on the MAIN supply inputs is detected. Circuit Breaker Function The MIC2591B provides an electronic circuit breaker function that protects against excessive loads, such as short circuits, at each supply. When the current from one or more of a slot's MAIN outputs exceeds the current limit threshold (ILIM = 50mV/RSENSE) for a duration greater than tFLT, the circuit breaker is tripped and both MAIN supplies (all outputs except VAUX[A/B]) are shut off. Should the load current cause a MAIN output's VSENSE to exceed VTHFAST, the outputs are immediately shut off with no delay. Undervoltage IGATE(3VCHARGE) t 3V(SOURCE_DRAIN) = t 3VDLY + x VGS(TH) Table 1. 3.3V and 12V Output Slew-Rate Selection for Gate Capacitance Dominated Start-up The 3.3V outputs act as source followers. In this mode of operation,VSOURCE = [VGATE - VTH(ON)] until the associated output reaches 3.3V. The voltage on the gate of the MOSFET will then continue to rise until it reaches 12V, which ensures minimum RDS(ON). Note that a delay exists between the ON command to a slot and the appearance of voltage at the slot's 3.3V output. This delay is the time required to charge the 3VGATE output up to the threshold voltage of the external MOSFET (typically about 3V). t 3VDLY = GATE(TOTAL) where CGATE(TOTAL) is the sum of the CGS of the external MOSFET, any external capacitance from the GATE output of the MIC2591B to the source of the MOSFET, and CMILLER (external, if used). Table 1 approximates the output slew-rate for various values of CGATE when start-up is dominated by GATE capacitance (external CGATE from GATE pin to ground plus CGS of the external MOSFET for the 3.3V rail; CMILLER for the 12V rail). | IGATE | = 25A CGATE or CMILLER dv/dt (load) 0.01F* 2.5V/ms 0.022F* 1.136V/ms where IGATE is the GATE pin current, IGATE(3VCHARGE) or IGATE(12VSINK), CLOAD is the load capacitance, and CGATE is the total GATE capacitance (CISS of the external MOSFET and any external capacitance connected from the GATE output pin to the GATE reference - GND or source). For the 3.3V outputs and 12V outputs (if no external 12VGATE output capacitors are implemented), the following equation is used to determine the output slew rate. dVOUT / dt = (C 14 M9999-082004 MIC2591B Micrel conditions on the MAIN supply inputs also trip the circuit breaker, but only when the MAIN outputs are enabled (to signal a supply input brown-out condition). The VAUX[A/B] outputs have a different circuit-breaker function. The VAUX[A/B] circuit breakers do not incorporate a fast-trip detector, instead they regulate the output current into a fault to avoid exceeding their operating current limit. The circuit breaker will trip due to an overcurrent on VAUX[A/B] when the fault timer expires. This use of the tFLT timer prevents the circuit breaker from tripping prematurely due to brief current transients. Following a fault condition, the outputs can be turned on again via the ON inputs (if the fault occurred on one of the MAIN outputs), via the AUXEN inputs (if the fault occurred on the AUX outputs), or by cycling both ON and AUXEN (if faults occurred on both the MAIN and AUX outputs). A fault condition can alternatively be cleared under SMI control of the ENABLE bits in the CNTRL[A/B] registers (see Register Bits D[1:0]). When the circuit breaker trips, /FAULT[A/B] will be asserted if the outputs were enabled through the Hot-Plug Interface inputs. At the same time, /INT will be asserted (unless interrupts are masked). Note that /INT is deasserted by writing a Logic 1 back into the respective fault bit position(s) in the STAT[A/B] register or the Common Status Register. The response time (tFLT) of the MIC2591B's primary overcurrent detector is set by external capacitors at the CFILTER[A/B] pins to GND. For Slot A, CFILTER[A] is located at Pin 2; for Slot B, CFILTER[B] is located at Pin 35. For a given response time, the value for CFILTER[A/B] is given by: CFILTER[A /B] (F) = tFLT[ A / B] (ms) x IFILTER (A ) VFILTER (V) x 10 3 where tFLT[A/B] is the desired response time and quantities IFILTER and VFILTER are specified in the MIC2591B's "Electrical Characteristics" table. For applications that require a more accurate response time for a given CFILTER[A/B] tolerance, the MIC2591B employs a patent-pending technique that improves response time accuracy by more than a factor of two. A 110k, 1% resistor connected from the MIC2591B's RFILTER[A&B] pin (Pin 20) to GND can be used. In this case, the value for CFILTER[A/B] for a desired response time (tFLT) is given by: CFILTER[A /B] (F) = tFLT (ms) RFILTER[A /B] (k) x SF where tFLT is the desired response time, RFILTER[A&B] is 110k, and "SF" is the CFILTER[A/B] response time "Scaling Factor" in the "Electrical Characteristics" table. Thermal Shutdown The internal VAUX[A/B] MOSFETs are protected against damage not only by current limiting, but by dual-mode overtemperature protection as well. Each slot controller on the MIC2591B is thermally isolated from the other. Should an overcurrent condition raise the junction temperature of one slot's controller and pass elements to 140C, all of the outputs for that slot (including VAUX) will be shut off and the slot's /FAULT output will be asserted. The other slot's operating VSTBY (1) AUXEN[A/B] (2) VAUX[A/B] 3VAUX_UV[A/B] 4.99 k (3) /PWRGD[A/B] (1) ON[A/B] (4) MAIN[A/B] (3) 12VOUT_UV[A/B] 3VOUT_UV[A/B](3) (1) FORCE_ON[A/B] (5) FORCE_EN[A/B] (1) (2) (3) (4) (5) External pin CNTRL[A/B] Register Bit D[0] Internal flag CNTRL[A/B] Register Bit D[1] CNTRL[A/B] Register Bit D[2] Figure 7. /PWRGD[A/B] Logic Diagram August 2004 15 M9999-082004 MIC2591B Micrel be enabled after the power-on-reset delay, tPOR (typically, 250s), has elapsed. The timing response diagram of Figure 8 illustrates a Hot-Plug Interface operation where an overcurrent fault is detected by the MIC2591B controller after initiating a power-up sequence. The MAIN (+12V & +3.3V) and VAUX[A/B] supply rails, /FAULT, /PWRGD and /INT output responses for both AUX and MAIN are shown in the figure. System Management Interface (SMI) The MIC2591B's System Management Interface uses the Read_Byte and Write_Byte subset of the SMBus protocols to communicate with its host via the System Management Interface bus. The /INT output signals the controlling processor that one or more events need attention, if an interruptdriven architecture is used. Note that the MIC2591B does not participate in the SMBus Alert Response Address (ARA) portion of the SMBus protocol. Fault Reporting and Interrupt Generation condition will remain unaffected. However, should the MIC2591B's die temperature exceed 160C, both slots (all outputs, including VAUXA and VAUXB) will be shut off, whether or not a current limit condition exists. A 160C overtemperature condition additionally sets the overtemperature bit (OT_INT) in the Common Status Register. /PWRGD[A/B] Outputs The MIC2591B has two /PWRGD outputs, one for each slot. These are open-drain, active-low outputs that require an external pull-up resistor to VSTBY. Each output is asserted when a slot has been enabled and has successfully begun delivering power to its respective +12V, +3.3V, and VAUX outputs. An equivalent logic diagram for /PWRGD[A/B] is shown in Figure 7. /FORCE_ON[A/B] Inputs These level-sensitive, active-low inputs are provided to facilitate designing systems using the MIC2591B. Asserting /FORCE_ON[A/B] will turn on all three of the respective slot's outputs (+12V, +3.3V, and VAUX), while specifically defeating all protections for those outputs. This explicitly includes all overcurrent and short circuit protections, and on-chip thermal protection for the VAUX outputs. Additionally, asserting a slot's /FORCE_ON[A/B] input will disable all of its input and output UVLO protections, with the sole exception of that asserting either or both of the /FORCE_ON[A/B] inputs will not disable the VSTBY[A/B] input UVLO. Asserting /FORCE_ON[A/B] will cause the respective slot's /PWRGD[A/B] and /FAULT[A/B] outputs to enter their opendrain state. Additionally, there are two SMBus accessible register bits (see CNTRL[A/B] Register Bit D[2]), which can be set to disable the corresponding slot's /FORCE_ON[A/B] pins. This allows system software to prevent these hardware overrides from being inadvertently activated during normal use. If not used, each pin should be connected to VSTBY using an external pull-up resistor. See Figure 6 for details. General Purpose Input (GPI) Pins Two pins on the MIC2591B are available for use as GPI pins. The logic state of each of these pins can be determined by polling Bits [4:5] of Common Status Register. Both of these inputs are compliant to 3.3V. If unused, connect each GPI_[A0/B0] pin to GND. A/D Converter The MIC2591B has an internal 12-channel, 8-bit A/D converter that monitors the output voltage and current of each supply. This information is available via the System Management Interface. While the information is particularly intended for use by systems that support the IPMI 1.0 standard, it may be used for any other desired purpose. A 23.2k external resistor must be connected from the IREF pin to ground to set the A/D Converter's Full-Scale current reference for the VAUX[A/B] internal MOSFETs. Hot-Plug Interface (HPI) Once the input supplies are above their respective UVLO thresholds, the Hot-Plug Interface can be utilized for power control by enabling the control input pins (AUXEN[A/B] and ON[A/B]) for each slot. In order for the MIC2591B to switch on the VAUX supply for either slot, the AUXEN[A/B] control must August 2004 SMI-only Control Applications In applications where the MIC2591B is controlled only by the SMI, ON[A/B] and AUXEN[A/B] are connected to GND and the /FORCE_ON[A/B] pins are connected to VSTBY as shown in Figure 6. In this case, the MIC2591B's /FAULT[A/B] outputs and STAT[A/B] Register Bit D[7] (FAULT[A/B]) are not activated as fault status is determined by polling STAT[A/B] Register Bits D[4], D[2], D[0] and CS (Common Status) Register Bits D[2:1]. Individual fault bits in STAT[A/B] and CS registers are asserted after power-on-reset when: * Either or both CNTRL[A/B] Register Bits D[1:0] are asserted, AND * 12VIN[A/B], 3VIN[A/B], or VSTBY[A/B] input voltage is lower than its respective ULVO threshold, OR * The fast OC circuit breaker[A/B] has tripped, OR * The slow OC circuit breaker[A/B] has tripped AND its filter timeout has expired, OR * The slow OC circuit breaker[A/B] has tripped AND Slot[A/B] die temperature > 140C, OR * The MIC2591B's global die temperature > 160C To clear any one or all STAT[A/B] Register Bits D[4], D[2], D[0] and/or CS Register Bits D[2], D[1] once asserted, a software subroutine can perform an "echo reset" where a Logical "1" is written back to those register bit locations that have indicated a fault. This method of "echo reset" allows data to be retained in the STAT[A/B] and/or CS registers until such time as the system is prepared to operate on that data. The MIC2591B can operate in interrupt mode or polled mode. For interrupt-mode operation, the open-drain, active-LOW /INT output signal is activated after power-on-reset if the INTMSK bit (CS Register Bit D[3]) has been reset to Logical "0". Once activated, the /INT output is asserted by any one of the fault conditions listed above and deasserted when one or all STAT[A/B] Register Bits D[4], D[2], D[0] and/or CS Register Bits D[2], D[1] are reset upon the execution of an SMBus "echo reset" WRITE_BYTE cycle. For polled-mode operation, the INTMSK bit should be set to Logical "1," thereby inhibiting /INT output pin operation. 16 M9999-082004 MIC2591B Micrel +3.3V UVLO VSTBY 0 VIH AUXEN[A/B] VIH VIL 0 tPOR VAUX_OUT[A/B] 0 ILIM(AUX) tFLT IAUX_OUT[A/B] ISTEADY-STATE 0 VIH VIH ON[A/B] VIL 0 12VOUT[A/B] 0 3VOUT[A/B] 0 /PWRGD_[A/B] 0 ILIM(3V) tFLT I3VOUT[A/B] ISTEADY-STATE 0 /FAULT_[A/B] 0 * /INT* * 0 * /INT de-asserted by software Figure 8. Hot-Plug Interface Operation MIC2591B Device Address Command Byte to MIC2591B Data Byte to MIC2591B DATA S 1 0 0 0 A2 A1 A0 0 A 0 0 0 0 0 0 X X A D7 D6 D5 D4 D3 D2 D1 D0 A P START R/W = WRITE ACKNOWLEDGE ACKNOWLEDGE ACKNOWLEDGE STOP CLK Master to device transfer, i.e., DATA driven by master. Device to master transfer, i.e., DATA driven by device. Figure 9. WRITE_BYTE Protocol MIC2591B Device Address Command Byte to MIC2591B MIC2591B Device Address Data Read From MIC2591B DATA S 1 0 0 0 A2 A1 A0 0 A 0 0 0 0 0 0 X X A S 1 0 0 0 A2 A1 A0 1 A D7 D6 D5 D4 D3 D2 D1 D0 /A P START R/W = WRITE ACKNOWLEDGE ACKNOWLEDGE R/W = READ START ACKNOWLEDGE NOT ACKNOWLEDGE STOP CLK Master to device transfer, i.e., DATA driven by master. Device to master transfer, i.e., DATA driven by device. Figure 10. READ_BYTE Protocol MIC2591B Device Address Byte Read from MIC2591B DATA S 1 0 0 0 A2 A1 A0 1 A D7 D6 D5 D4 D3 D2 D1 D0 /A P START R/W = READ ACKNOWLEDGE NOT ACKNOWLEDGE STOP CLK Master to device transfer, i.e., DATA driven by master. Device to master transfer, i.e., DATA driven by device. Figure 11. RECEIVE_BYTE Protocol August 2004 17 M9999-082004 MIC2591B Micrel For those SMI-control applications where the /FORCE_ON[A/B] inputs are needed for diagnostic purposes, the /FORCE_ON[A/B] inputs must be enabled; that is, CNTRL[A/B] Register Bit D[2] should read Logical "0." Once /FORCE_ON[A/B] inputs are asserted, all output voltages are present with all circuit protection features disabled, including overtemperature protection on VAUX[A/B] outputs. To inhibit /FORCE_ON[A/B] operation, a Logical "1" shall be written to the CNTRL[A/B] Register Bit D[2] location(s). write and read operation: the host first sends the device's target address followed by the command byte, as in a write operation. A new "Start" bit must then be sent to the MIC2591B, followed by a repeat of the device address with the R/W bit set to the high (read) state. The data to be read from the part may then be clocked out. There is one exception to this rule: If the location latched in the pointer register from the last write operation is known to be correct (i.e., points to the desired register within the MIC2591B), then the "Receive_Byte" procedure may be used. To perform a Receive_Byte operation, the host sends an address byte to select the target MIC2591B, with the R/W bit set to the high (read) state, and then retrieves the data byte. Figures 9 through 11 show the formats for these data read and data write procedures. The Command Register is eight bits (one byte) wide. This byte carries the address of the MIC2591B's register to be operated upon. The command byte values corresponding to the various MIC2591B register addresses are shown in Table 2. Command byte values other than 0000 0XXXb = 00h - 07h are reserved and should not be used. MIC2591B SMBus Address Configuration The MIC2591B responds to its own unique SMBus address, which is assigned using A2, A1, and A0. These represent the 3 LSBs of its 7-bit address, as shown in Table 3. These address bits are assigned only during power up of the VSTBY[A/B] supply input. These address bits allow up to eight MIC2591B devices in a single system. These pins are either grounded or left unconnected to specify a logical 0 or logical 1, respectively. A pin designated as a logical 1 may also be pulled up to VSTBY. HPI-only Control Applications In applications where the MIC2591B is controlled only by the HPI, SMBus signals SCL, SDA, and /INT signals are connected to VSTBY as shown in Figure 6. In this configuration, the MIC2591B's /FAULT[A/B] outputs are activated after power-on-reset and become asserted when: Either or both external ON[A/B] and AUXEN[A/B] input signals are asserted, AND * 12VIN[A/B], 3VIN[A/B], or VSTBY[A/B] input voltage is lower than its respective ULVO threshold, OR * The fast OC circuit breaker[A/B] has tripped, OR * The slow OC circuit breaker[A/B] has tripped AND its filter timeout[A/B] has expired, OR * The slow OC circuit breaker[A/B] has tripped AND Slot[A/B] die temperature > 140C, OR * The MIC2591B's global die temperature > 160C In order to clear /FAULT[A/B] outputs once asserted, either or both ON[A/B] and AUXEN[A/B] input signals must be deasserted. Please see /FAULT[A/B] pin description for additional information. If the /FORCE_ON[A/B] inputs are used for diagnostic purposes, both /FAULT[A/B] and /PWRGD[A/B] outputs are deasserted once /FORCE_ON[A/B] inputs are asserted. Serial Port Operation The MIC2591B uses standard SMBus Write_Byte and Read_Byte operations for communication with its host. The SMBus Write_Byte operation involves sending the device's target address, with the R/W bit (LSB) set to the low (write) state, followed by a command byte and a data byte. The SMBus Read_Byte operation is similar, but is a composite A2 0 0 0 0 1 1 1 1 Table 3. MIC2591B SMBus Addressing Command Byte Value Power-On Default Target Register August 2004 A0 0 1 0 1 0 1 0 1 MIC2591B Device Address Binary Hex 1000 000X*b 80h 1000 001Xb 82h 1000 010Xb 84h 1000 011Xb 86h 1000 100Xb 88h 1000 101Xb 8Ah 1000 110Xb 8Ch 1000 111Xb 8Eh * Where X = '1' for READ and '0' for WRITE MIC2591B Register Set and Programmer's Model Label RESULT ADC_CNTRL CNTRLA CNTRLB STATA STATB CS Reserved Inputs A1 0 0 1 1 0 0 1 1 Description Read ADC Conversion Result Register 00h ADC Control Register 01h Control Register Slot A 02h Control Register Slot B 03h Slot A Status 04h Slot B Status 05h Common Status Register 06h Reserved / Do Not Use 07h - FFh Table 2. MIC2591B Register Addresses 18 Write na 01h 02h 03h 04h 05h 06h 07h - FFh xxh 00h 00h 00h 00h 00h xxxx 0000b Undefined M9999-082004 MIC2591B Micrel Detailed Register Descriptions Converter Result Register (RESULT) 8-Bits, Read-Only D[7] read-only Bit D[7:0] D[6] read-only Conversion Result Register (RESULT) D[5] D[4] D[3] D[2] read-only read-only read-only read-only Voltage or Current Data from ADC Function Measured data from ADC Power-Up Default Value: Read Command Byte: PAR SUP[2:0] read-only xxxx xxxxb = xxh 0000 0000b = 00h Function D[1] read/write Supply Select SUP[2:0] D[0] read/write Operation 0 = ADC quiescent, 1 = ADC busy Always read as zero Always read as zero Specifies slot for A/D conversion 0 = Slot A, 1 = Slot B 1 = Voltage, 0 = Current 000 = No conversion 001 = +3.3V supply 010 = Undefined - Do Not Use 011 = +12V supply 100 = Undefined - Do Not Use 101 = VAUX supply ADC status Reserved Reserved A/D Slot Select Parameter control bit for ADC conversion Supply select for ADC conversion Power-Up Default Value: Command_Byte Value (R/W): 0000 0000b = 00h 0000 0001b = 01h To operate the ADC, the ADC_CNTRL register must be accessed with the following parameters: * Selection of which slot will provide the parameter to be measured (Register Bit D[4]) * Choice of whether voltage or current is to be reported (Register Bit D[3]) * Selection of the which supply that is to be monitored (Register Bit D[2:0]) August 2004 D[0] read-only Operation ADC Control Register (ADC_CNTRL) 8-Bits, Read/Write ADC Control Register (ADC_CNTRL) D[7] D[6] D[5] D[4] D[3] D[2] read-only read-only read-only read/write read/write read/write BUSY Reserved Reserved SEL PAR Bit(s) BUSY D[6] D[5] SEL D[1] read-only Note that this data may all be contained within one write to the ADC_CNTRL register. Software must then poll the BUSY bit (D[7]) until it is zero, or wait for a period of 100ms. At the end of that time, the RESULT register will contain the results of the conversion. After reading the RESULT register, a new conversion may be started. 19 M9999-082004 MIC2591B Micrel Control Register, Slot A (CNTRLA) 8-Bits, Read/Write D[7] read-only AUXAPG D[6] read-only MAINAPG Control Register, Slot A (CNTRLA) D[5] D[4] D[3] read only read only read-only Reserved Reserved Reserved Bit(s) AUXAPG Function AUX output power-good status, Slot A MAINAPG MAIN output power-good status, Slot A D[5] D[4] D[3] /FORCE_A ENABLE MAINA VAUXA Reserved Reserved Reserved Allows or inhibits the operation of the /FORCE_ONA input pin MAIN enable control, Slot A VAUX enable control, Slot A Power-Up Default Value: Read Command_Byte Value (R/W): D[2] read/write /FORCE_A ENABLE D[1] read/write MAINA D[0] read/write VAUXA Operation 1 = Power-is-Good (VAUXA Output is above its UVLO threshold) 1 = Power-is-Good (MAINA Outputs are above their UVLO thresholds) Always read as zero Always read as zero Always read as zero 0 = /FORCE_ONA is enabled 1 = /FORCE_ONA is disabled 0 = Off, 1 = On 0 = Off, 1 = On 0000 0000b = 00h 0000 0010b = 02h The power-up default value is 00h. Slot is disabled upon power-up, i.e., all supply outputs are off. Notes: 1. The state of the /PWRGDA pin is the logical AND of the values of the AUXAPG and the MAINAPG bits, except when /FORCE_ONA is asserted. If /FORCE_ONA is asserted (the pin is pulled low), and /FORCE_AENABLE is set to a logic zero, the /PWRGDA pin will be unconditionally forced to its open-drain ("Power Not Good") state. 2. The values of the MAINAPG and AUXAPG register bits are not affected by /FORCE_ONA, but will instead continue to read as high if power is "Good," and as low if the conditions which indicate that power is good are not met. August 2004 20 M9999-082004 MIC2591B Micrel Control Register, Slot B (CNTRLB) 8-Bits, Read/Write D[7] read-only AUXBPG D[6] read-only MAINBPG Control Register, Slot B (CNTRLB) D[5] D[4] D[3] read only read only read-only Reserved Reserved Reserved Bit(s) AUXBPG Function AUX output power-good status, Slot B MAINBPG MAIN output power-good status, Slot B D[5] D[4] D[3] /FORCE_B ENABLE MAINB VAUXB Reserved Reserved Reserved Allows or inhibits the operation of the /FORCE_ONB input pin MAIN enable control, Slot B VAUX enable control, Slot B Power-Up Default Value: Command_Byte Value (R/W): D[2] read/write /FORCE_B ENABLE D[1] read/write MAINB D[0] read/write VAUXB Operation 1 = Power-is-Good (VAUXB Output is above its UVLO threshold) 1 = Power-is-Good (MAINB Outputs are above their UVLO thresholds) Always read as zero Always read as zero Always read as zero 0 = /FORCE_ONB is enabled 1 = /FORCE_ONB is disabled 0 = Off, 1 = On 0 = Off, 1 = On 0000 0000b = 00h 0000 0011b = 03h The power-up default value is 00h. Slot is disabled upon power-up, i.e., all supply outputs are off. Notes: 1. The state of the /PWRGDB pin is the logical AND of the values of the AUXBPG and the MAINBPG bits, except when /FORCE_ONB is asserted. If / FORCE_ONB is asserted (the pin is pulled low), and /FORCE_BENABLE is set to a logic zero, the /PWRGDB pin will be unconditionally forced to its open-drain ("Power Not Good") state. 2. The values of the MAINBPG and AUXBPG register bits are not affected by /FORCE_ONB, but will instead continue to read as high if power is "Good," and as low if the conditions which indicate that power is good are not met. August 2004 21 M9999-082004 MIC2591B Micrel Status Register Slot A (STATA) 8-Bits, Read-Only D[7] read-only FAULTA Bit(s) FAULTA D[6] read-only MAINA Status Register, Slot A (STATA) D[5] D[4] D[3] read-only read/write read-only VAUXA VAUXAF Reserved Function FAULT Status - Slot A MAINA MAIN Enable Status - Slot A VAUXA VAUX Enable Status - Slot A VAUXAF D[3] 12VAF D[1] 3VAF D[1] read-only Reserved D[0] read/write 3VAF Operation 1 = Fault pin asserted (/FAULTA pin is LOW) 0 = Fault pin deasserted (/FAULTA pin is HIGH) See Notes 1, 2, and 3. Represents the actual state (on/off) of the two Main Power outputs for Slot A (+12V and +3.3V) 1 = Main Power ON 0 = Main Power OFF Represents the actual state (on/off) of the Auxiliary Power output for Slot A 1 = AUX Power ON 0 = AUX Power OFF 1 = Fault 0 = No fault Always read as zero 1 = Fault 0 = No fault Always read as zero 1 = Fault 0 = No fault Overcurrent Fault: VAUXA supply Reserved Overcurrent Fault: +12V supply Reserved Overcurrent Fault: 3.3V supply Power-Up Default Value: Command_Byte Value (R/W): D[2] read/write 12VAF 0000 0000b = 00h 0000 0100b = 04h The power-up default value is 00h. Both slots are disabled upon power-up, i.e., all supply outputs are off. In response to an overcurrent fault condition, writing a logical 1 back into the active (or set) bit position will clear the bit and deassert /INT. The status of the /FAULTA pin is not affected by reading the Status Register or by clearing active status bits. Notes: 1. If FAULTA has been set by an overcurrent condition on one or more of the MAIN outputs, the ONA input must go LOW to reset FAULTA. If FAULTA has been set by a VAUXA overcurrent event, the AUXENA input must go LOW to reset FAULTA. If an overcurrent has occurred on both a MAIN output and the VAUX output of slot A, both ONA and AUXENA of the slot must go low to reset FAULTA. 2. Neither the FAULTA bits nor the /FAULTA pins are active when the MIC2591B power paths are controlled by the System Management Interface. When using SMI power path control, AUXENA and ONA pins for that slot must be tied to GND. 3. If /FORCE_ONA is asserted (low), the /FAULTA pin will be unconditionally forced to its open-drain state. Note, though, that the value in the FAULTA register bit is not affected by /FORCE_ONA, but will instead continue to read as a high if no faults are present on Slot A, and as a low if any fault conditions exist which would disable Slot A if /FORCE_ONA was not asserted. August 2004 22 M9999-082004 MIC2591B Micrel Status Register Slot B (STATB) 8-Bits, Read-Only D[7] read-only FAULTB Bit(s) FAULTB D[6] read-only MAINB Status Register, Slot B (STATB) D[5] D[4] D[3] read-only read/write read-only VAUXB VAUXBF Reserved Function FAULT Pin Status - Slot B MAINB MAIN Enable Status - Slot B VAUXB VAUX Enable Status - Slot B VAUXBF D[3] 12VBF D[1] 3VBF D[1] read-only Reserved D[0] read/write 3VBF Operation 1 = Fault pin asserted (/FAULTB pin is LOW) 0 = Fault pin deasserted (/FAULTB pin is HIGH) See Notes 1, 2, and 3. Represents the actual state (on/off) of the four Main Power outputs for Slot B (+12V and +3.3V) 1 = MAIN Power ON 0 = MAIN Power OFF Represents the actual state (on/off) of the Auxiliary Power output for Slot B 1 = AUX Power ON 0 = AUX Power OFF 1 = Fault 0 = No fault Always read as zero 1 = Fault 0 = No fault Always read as zero 1 = Fault 0 = No fault Overcurrent Fault: VAUXB supply Reserved Overcurrent Fault: +12V supply Reserved Overcurrent Fault: 3.3V supply Power-Up Default Value: Command_Byte Value (R/W): D[2] read/write 12VBF 0000 0000b = 00h 0000 0101b = 05h The power-up default value is 00h. Both slots are disabled upon power-up, i.e., all supply outputs are off. In response to an overcurrent fault condition, writing a logical 1 back into the active (or set) bit position will clear the bit and deassert /INT. The status of the /FAULTB pin is not affected by reading the Status Register or by clearing active status bits. Notes: 1. If FAULTB has been set by an overcurrent condition on one or more of the MAIN outputs, the ONB input must go LOW to reset FAULTB. If FAULTB has been set by a VAUXB overcurrent event, the AUXENB input must go LOW to reset FAULTB. If an overcurrent has occurred on both a MAIN output and the VAUX output of slot B, both ONB and AUXENB of the slot must go low to reset FAULTB. 2. Neither the FAULTB bits nor the /FAULTB pins are active when the MIC2591B power paths are controlled by the System Management Interface. When using SMI power path control, the AUXENB and ONB pins for that slot must be tied to GND. 3:. If /FORCE_ONB is asserted (low), the /FAULTB pin will be unconditionally forced to its open-drain state. Note, though, that the value in the FAULTB register bit is not affected by /FORCE_ONB, but will instead continue to read as a high if no faults are present on Slot B, and as a low if any fault conditions exist which would disable Slot B if /FORCE_ONB was not asserted. August 2004 23 M9999-082004 MIC2591B Micrel Common Status Register (CS) 8-Bits, Read/Write D[7] read-write Reserved D[6] read-write Reserved Common Status Register (CS) D[5] D[4] D[3] read-only read-only read-write GPI_B0 GPI_A0 INTMSK Bit(s) D[7] D[6] GPI_B0 GPI_A0 INTMSK Reserved Reserved General Purpose Input 0, Slot B General Purpose Input 0, Slot A Interrupt Mask UV_INT Undervoltage Interrupt OT_INT Overtemperature Interrupt D[0] Function D[1] read-write OT_INT D[0] read-only Reserved Operation Always read as zero Always read as zero State of GPI_B0 pin State of GPI_A0 pin 0 = /INT generation is enabled 1 = /INT generation is disabled. The MIC2591B does not participate in the SMBus Alert Response Address (ARA) protocol 0 = No UVLO fault 1 = UVLO fault Set whenever a circuit breaker fault condition occurs as a result of an undervoltage lockout condition on one of the main supply inputs. This bit is only set if a UVLO condition occurs while the ON[A/B] pin is asserted or the MAIN[A/B] control bits are set 0 = Die Temp < 160C. 1 = Fault: Die Temp > 160C. Set if a fault occurs as a result of the MIC2591B's die temperature exceeding 160C Undefined Reserved Power-Up Default Value: Command_Byte Value (R/W): D[2] read-write UV_INT 00000000b = 00h 00000110b = 06h To reset the OT_INT and UV_INT fault bits, a logical 1 must be written back to these bits. August 2004 24 M9999-082004 MIC2591B Micrel Package Information MICREL, INC. TEL 1849 FORTUNE DRIVE SAN JOSE, CA 95131 + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB USA http://www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2004 Micrel, Incorporated. August 2004 25 M9999-082004