19-1013; Rev 1; 7/08 KIT ATION EVALU E L B AVAILA Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability Features The MAX16050 monitors up to 5 voltages and sequences up to 4 voltages, while the MAX16051 monitors up to 6 voltages and sequences up to 5 voltages. These devices provide an adjustable delay as each supply is turned on and they monitor each power-supply voltage. When all of the voltages reach their final values and the reset delay timer expires, a power-on-reset (POR) output deasserts allowing the microcontroller (C) to operate. If any voltage falls below its threshold, the reset output asserts and all voltage supplies are turned off. The MAX16050/MAX16051 can be daisy-chained to control a higher number of voltages in a system. o Monitor Up to 6 Voltages/Sequence Up to 5 Voltages o Pin-Selectable Sequencing Order (MAX16050 Only) o Reverse-Sequencing Capability on Shutdown o Overvoltage Monitoring with Independent Output o 1.5% Threshold Accuracy o 2.7V to 13.2V Operating Voltage Range o Charge Pump to Fully Enhance External n-Channel FETs o Capacitor-Adjustable Sequencing Delay o Fixed or Capacitor-Adjustable Reset Timeout o Internal 85mA Pulldowns for Discharging Capacitive Loads Quickly o Daisy-Chaining Capability to Communicate Across Multiple Devices o Small 4mm x 4mm, 28-Pin TQFN Package OUT1 DISC1 REM 20 OV_OUT 21 SET1 TOP VIEW RESET Pin Configurations FAULT During a power-down event, the MAX16050/MAX16051 can reverse sequence the outputs. In this situation, each voltage is turned off sequentially until it reaches a 250mV level, at which point, the next supply is turned off. The MAX16050/MAX16051 also provide internal pulldown circuitry that turns on during power-down, to help discharge large output capacitors. The MAX16050/MAX16051 feature a charge-pump supply output that can be used as a pullup voltage for driving external n-channel MOSFETs and an overvoltage output that indicates when any of the monitored voltages exceeds its overvoltage threshold. The MAX16050 also provides three sequence control inputs for changing the sequence order, while the MAX16051 has a fixed sequence order. The MAX16050/MAX16051 are available in a 28-pin (4mm x 4mm) thin QFN package and are fully specified over the -40C to +85C extended operating temperature range. 19 18 17 16 15 SHDN 22 14 EN_HOLD DELAY 23 13 DISC2 TIMEOUT 24 12 OUT2 SEQ1 25 11 SET2 10 DISC3 9 OUT3 8 SET3 MAX16050 SEQ2 26 SEQ3 27 Applications *EP + 3 4 Networking Systems 6 7 THIN QFN (4mm x 4mm) *EP = EXPOSED PAD Typical Operating Circuit appears at end of data sheet. 5 DISC4 2 SET4 1 OUT4 Storage Systems EN Workstations ABP Telecom Equipment VCC Servers GND CP_OUT 28 Pin Configurations continued at end of data sheet. Ordering Information TEMP RANGE PIN-PACKAGE MONITORED VOLTAGES VOLTAGES SEQUENCED MAX16050ETI+ -40C to +85C 28 TQFN-EP* 5 4 MAX16051ETI+ -40C to +85C 28 TQFN-EP* 6 5 PART +Denotes lead-free/RoHS-compliant package. *EP = Exposed pad. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX16050/MAX16051 General Description MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND.) VCC .........................................................................-0.3V to +30V REM, OUT_, DISC_.................................................-0.3V to +30V RESET, SHDN, SET_, FAULT, EN_HOLD, EN, DELAY, OV_OUT, ABP, TIMEOUT, SEQ_...........................-0.3V to +6V CP_OUT.........................................................-0.3V to (VCC + 6V) RESET Current ....................................................................50mA DISC_ Current ...................................................................180mA Input/Output Current (all other pins) ...................................20mA Continuous Power Dissipation (TA = +70C) 28-Pin (4mm x 4mm) Thin QFN (derate 28.6mW/C above +70C) ............................................................2285mW* Operating Temperature Range ...........................-40C to +85C Junction Temperature .....................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C *As per JEDEC51 Standard (Multilayer Board). Stresses beyond 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 beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VCC = 2.7V to 13.2V, VEN = VABP, TA = TJ = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) SYMBOL CONDITIONS MIN Operating Voltage Range (Note 2) PARAMETER VCC Voltage on VCC to ensure the device is fully operational 2.7 Operating Voltage VCCR VDISC_ = VOUT_ = VRESET = low, voltage on VCC falling Regulated Supply Voltage VABP IABP = 1mA (external sourcing current from ABP) 2.45 Minimum voltage on ABP, ABP rising 2.1 Undervoltage Lockout Undervoltage Lockout Hysteresis Supply Current VUVLO VUVLO_HYS ABP falling ICC VCC = 3.3V, all OUT_ = high, no load VTH SET_ falling VTH_HYS SET_ rising TYP MAX UNITS 13.2 V 1.1 V 2.90 V 2.3 V 100 mV 0.7 1.1 mA 0.5 0.508 V MONITORED ANALOG INPUTS SET_ Threshold SET_ Threshold Hysteresis 0.492 0.5 %VTH SET1-SET4 Input Current ISET VSET_ = 0.5V -100 +100 nA SET5 Input Current ISET5 VSET5 = 0.5V (MAX16051 only) -100 +100 nA SET_ rising 0.541 SET_ Threshold Tempco Overvoltage Threshold VTH/_TC VTH_OV Overvoltage Threshold Hysteresis 30 SET_ falling EN Threshold VTH_EN EN_ falling EN Threshold Hysteresis VEN_HYS EN_ rising IEN VEN = 0.5V EN Input Current 0.55 ppm/C 0.558 0.5 0.492 0.5 0.508 0.5 -100 V %VTH_OV V %VTH_EN +100 nA SEQUENCING, CAPACITOR DISCHARGE, AND SEQUENCE TIMING OUTPUTS VCC = 3.3V, ISINK = 3.2mA 0.3 VCC = 1.8V, ISINK = 100A 0.3 OUT_ Output Low Voltage VOL_OUT OUT_ Leakage Current ILKG_OUT VOUT_ = 12V, OUT_ asserted DISC_ Output Pulldown Current IOL_DISC Pulldown current during fault condition or power-down mode, VDISC_ = 1V DISC_ Output Leakage Current ILKG_DISC VDISC_ = 3.3V, not in power-down mode DISC_ Power Low Threshold 2 VTH_PL DISC_ falling 1 85 200 250 _______________________________________________________________________________________ V A mA 1 A 300 mV Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability (VCC = 2.7V to 13.2V, VEN = VABP, TA = TJ = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL DELAY, TIMEOUT Output Source Current IDT DELAY, TIMEOUT Threshold Voltage CONDITIONS VDELAY = VTIMEOUT = 0V VTH_DT MIN TYP MAX UNITS 1.6 2.5 3.0 A 1.218 1.250 1.281 V 0.4 V DIGITAL INPUTS/OUTPUTS SHDN, FAULT, EN_HOLD InputLogic Low Voltage VIL SHDN, FAULT, EN_HOLD InputLogic High Voltage VIH EN_HOLD Input Current II EN_HOLD to OUT Delay tEN_OUT FAULT, SHDN to ABP Pullup Resistance tOUT RESET Output Low Voltage VOL VOL_RF V 1 3 60 RP SHDN to OUT_ Delay REM, FAULT Output Low Voltage 2 100 s 160 12 0.3 VCC = 1.8V, ISINK = 100A 0.3 VCC = 3.3V, ISINK = 3.2mA 0.3 tFAULT_PW SET_ to FAULT Delay Time tSET_FAULT SET_ falling below respective threshold 1.9 VIH_SEQ MAX16050 only VABP 0.35 SEQ1-SEQ3 Logic HighImpedance (No Connect) Level VIX_SEQ MAX16050 only 0.92 SEQ1-SEQ3 Logic-Low Level VIL_SEQ MAX16050 only SEQ1-SEQ3 High-Impedance State Tolerance Current IIX MAX16050 (Note 3) V V s 2.5 SEQ1-SEQ3 Logic-High Level k s VCC = 3.3V, ISINK = 3.2mA FAULT Pulse Width A s V -6 1.45 V 0.33 V +6 A 1 A 300 ms RESET CIRCUIT RESET, REM, OV_OUT Output Leakage ILKG VRESET = VREM = VOV_OUT = 5V RESET Timeout Period tRP TIMEOUT = ABP OUT_, FAULT, SHDN to RESET Delay tRST TIMEOUT = unconnected 50 128 3 s CHARGE-PUMP OUTPUT CP_OUT Voltage VCP_OUT ICP_OUT = 0.5A CP_OUT Source Current ICP_OUT VCP_OUT = VCC + 2V VCC + 4.6 VCC + 5 VCC + 5.8 V 17 25 30 A Note 1: Specifications are guaranteed for the stated global conditions, unless otherwise noted. 100% production tested at TA = +25C and TA = +85C. Specifications at TA = -40C are guaranteed by design. Note 2: When the voltage is below the VUVLO and above VCCR, OUT_ and RESET are asserted low. Note 3: SEQ1-SEQ3 are inputs with three logic levels: high, low, and high-impedance. _______________________________________________________________________________________ 3 MAX16050/MAX16051 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = 5V; VEN = VABP, TA = +25C, unless otherwise noted.) TA = +25C 600 550 TA = -40C 500 500 4.2 5.7 7.2 8.7 10.2 11.7 1.002 1.001 1.000 0.999 0.998 0.997 0.996 -15 10 35 85 60 -40 -15 10 35 60 TEMPERATURE (C) TEMPERATURE (C) NORMALIZED SEQUENCE DELAY vs. TEMPERATURE SEQUENCE DELAY vs. CDELAY NORMALIZED RESET TIMEOUT PERIOD vs. TEMPERATURE 1.15 1.10 CDELAY = OPEN 1.00 0.95 250 1.10 200 NORMALIZED RESET TIMEOUT PERIOD MAX16050/51 toc04 NORMALIZED AT TA = +25C 150 100 0.90 50 CDELAY = 0.1F 0.85 NORMALIZED AT TA = +25C 1.08 1.06 1.04 TIMEOUT = OPEN 1.02 1.00 0.98 0.96 TIMEOUT = ABP 0.94 0.92 0.80 0.90 0 -40 -15 10 35 60 85 0 100 TEMPERATURE (C) 200 300 -40 500 400 35 150 100 50 60 MAX16050/51 toc08 11 10 9 CP_OUT VOLTAGE (V) 200 10 TEMPERATURE (C) CP_OUT VOLTAGE vs. CP_OUT CURRENT MAX16050/51 toc07 250 RESET TIMEOUT PERIOD (ms) -15 CDELAY (nF) RESET TIMEOUT PERIOD vs. CTIMEOUT 8 7 6 5 4 3 2 1 0 0 0 100 200 300 CTIMEOUT (nF) 4 85 SUPPLY VOLTAGE (V) 1.20 1.05 1.003 0.995 -40 13.2 SEQUENCE DELAY (ms) 2.7 MAX16050/51 toc03 MAX16050/51 toc02 650 NORMALIZED AT TA = +25C VSET_ FALLING 1.004 MAX16050/51 toc06 550 TA = +85C 700 1.005 NORMALIZED SET_ THRESHOLD VOLTAGE 650 VCC = 5V ALL OUT_ = HIGH NO LOAD MAX16050/51 toc05 SUPPLY CURRENT (A) 700 750 SUPPLY CURRENT (A) MAX16050/51 toc01 750 600 NORMALIZED SET_ THRESHOLD VOLTAGE vs. TEMPERATURE SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT vs. SUPPLY VOLTAGE NORMALIZED SEQUENCE DELAY MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability 400 500 0 5 10 15 CP_OUT CURRENT (A) _______________________________________________________________________________________ 20 25 85 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability OV_OUT LOW VOLTAGE vs. SINK CURRENT 0.5 0.4 0.3 0.2 0.6 0.5 0.4 0.3 0.2 0.1 4 8 12 16 20 0.6 0.5 0.4 0.3 0.2 0 0 0 0.7 0.1 0.1 0 MAX16050/51 toc11 0.7 0.8 RESET LOW VOLTAGE (V) 0.6 MAX16050/51 toc10 OV_OUT LOW VOLTAGE (V) 0.7 0.8 OUT_ LOW VOLTAGE (V) MAX16050/51 toc09 0.8 RESET LOW VOLTAGE vs. SINK CURRENT OUT_ LOW VOLTAGE vs. SINK CURRENT 0 SINK CURRENT (mA) 4 8 12 16 20 0 4 REVERSE SEQUENCE POWER-DOWN USING SHDN (CDELAY = CTIMEOUT = OPEN) 8 20 MAX1650/51 toc13 SHDN 5V/div V1 5V/div EN 5V/div V1 5V/div V2 5V/div V2 5V/div V3 5V/div V3 5V/div V4 5V/div V4 5V/div 40s/div 40s/div DAISY-CHAINING TWO DEVICES WITH SHDN RISING (FIGURE 7) DAISY-CHAINING TWO DEVICES WITH SHDN FALLING (FIGURE 7) MAX1650/51 toc14a 100s/div 16 SIMULTANEOUS POWER-DOWN USING EN (CDELAY = CTIMEOUT = OPEN) MAX1650/51 toc12 CDELAY (U1) = CDELAY (U2) = 100pF SHDN = 5V/div V1-V7 = 5V/div 12 SINK CURRENT (mA) SINK CURRENT (mA) MAX1650/51 toc14b SHDN SHDN V1 V1 V2 V2 V3 V3 V4 V4 V5 V5 V6 V6 V7 V7 10s/div CDELAY (U1) = CDELAY (U2) = 100pF SHDN = 5V/div V1-V7 = 5V/div _______________________________________________________________________________________ 5 MAX16050/MAX16051 Typical Operating Characteristics (continued) (VCC = 5V; VEN = VABP, TA = +25C, unless otherwise noted.) MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability Pin Description PIN NAME FUNCTION MAX16050 MAX16051 1 1 VCC Device Power-Supply Input. Connect to 2.7V to 13.2V. Bypass VCC to GND with a 0.1F capacitor. 2 2 GND Ground 3 3 ABP Internal Supply Bypass Input. Connect a 1F capacitor from ABP to GND. ABP is an internally generated voltage and must not be used to supply more than 1mA to external circuitry. 4 4 EN Analog Enable Input. Connect a resistive divider at EN to monitor a voltage. The EN threshold is 0.5V. 5 5 SET4 Set Monitored Threshold 4 Input. Monitor a voltage by setting the threshold with an external resistive divider. The SET4 threshold is 0.5V. 6 6 OUT4 Open-Drain Output 4. When the voltage at SET3* is above 0.5V, OUT4 goes high impedance. OUT4 requires an external pullup resistor and can be pulled up to 13.2V. 7 7 DISC4 Discharge Pulldown Input 4. During normal operation, DISC4 is high impedance. During a fault condition or power-down, DISC4 provides an 85mA sink current. 8 8 SET3 Set Monitored Threshold 3 Input. Monitor a voltage by setting the threshold with an external resistive divider. The SET3 threshold is 0.5V. 9 9 OUT3 Open-Drain Output 3. When the voltage at SET2* is above 0.5V, OUT3 goes high impedance. OUT3 requires an external pullup resistor and can be pulled up to 13.2V. 10 10 DISC3 Discharge Pulldown Input 3. During normal operation, DISC3 is high impedance. During a fault condition or power-down, DISC3 provides an 85mA sink current. 11 11 SET2 Set Monitored Threshold 2 Input. Monitor a voltage by setting the threshold with an external resistive divider. The SET2 threshold is 0.5V. 12 12 OUT2 Open-Drain Output 2. When the voltage at SET1* is above 0.5V, OUT2 goes high impedance. OUT2 requires an external pullup resistor and can be pulled up to 13.2V. 13 13 DISC2 Discharge Pulldown Input 2. During normal operation, DISC2 is high impedance. During a fault condition or power-down, DISC2 provides an 85mA sink current. 14 14 15 15 REM Open-Drain Bus Removal Output. REM goes high impedance when all DISC_ inputs are below the DISC_ power low threshold (VTH_PL). REM goes low when any DISC_ input goes above VTH_PL. REM requires an external pullup resistor and can be pulled up to 13.2V. 16 16 DISC1 Discharge Pulldown Input 1. During normal operation, DISC1 is high impedance. During a fault condition or power-down, DISC1 provides an 85mA sink current. 17 17 OUT1 Open-Drain Output 1. When the voltage at EN* is above 0.5V, OUT1 goes high impedance. OUT1 requires an external pullup resistor and can be pulled up to 13.2V. Enable Hold Input. When EN_HOLD is low, the device does not start the reverseEN_HOLD sequencing process regardless of the status of the SHDN input. Reverse sequencing is allowed when this input is pulled high. Connect to ABP if unused. *This applies to the MAX16051. For the MAX16050, see Table 1 for the output sequence order. 6 _______________________________________________________________________________________ Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability PIN NAME MAX16050 MAX16051 18 18 SET1 19 19 OV_OUT 20 20 FUNCTION Set Monitored Threshold 1 Input. Monitor a voltage by setting the threshold with an external resistive divider. The SET1 threshold is 0.5V. Open-Drain Overvoltage Output. When any of the SET_ voltages exceed their 0.55V overvoltage threshold, OV_OUT goes low. When all of the SET_ voltages are below their overvoltage threshold, OV_OUT goes high impedance after a short propagation delay. RESET Open-Drain Reset Output. When any of the monitored voltages (including EN) falls below its threshold, SHDN is pulled low, or FAULT is pulled low, RESET asserts and stays asserted for at least the minimum reset timeout period after all of these conditions are removed. The reset timeout is 128ms (typ) when TIMEOUT is connected to ABP or can be adjusted by connecting a capacitor from TIMEOUT to GND. 21 21 FAULT FAULT Synchronization Input/Output. While EN = SHDN = high, FAULT is pulled low when any of the SET_ voltages falls below their respective threshold. Pull FAULT low manually to assert a simultaneous power-down. FAULT is internally pulled up to ABP by a 100k resistor. 22 22 SHDN Active-Low Shutdown Input. When SHDN is pulled low, the device will reverse sequence for power-down operation. SHDN is internally pulled up to ABP by a 100k resistor. 23 23 DELAY Adjustable Sequence Delay Timing Input. Connect a capacitor from DELAY to GND to set the sequence delay between each OUT_. Leave DELAY unconnected for a 10s (typ) delay. 24 24 TIMEOUT Adjustable Reset Timeout Input. Connect a capacitor from TIMEOUT to GND to set the reset timeout period. Connect TIMEOUT to ABP for the fixed timeout of 128ms (typ). Leave TIMEOUT unconnected for a 10s (typ) delay. 25 -- SEQ1 26 -- SEQ2 27 -- SEQ3 28 28 CP_OUT Charge-Pump Output. An internal charge pump boosts CP_OUT to (VCC + 5V ) to provide a pullup voltage that can be used to drive external n-channel MOSFETs. CP_OUT sources up to 25A. -- 25 DISC5 Discharge Pulldown Input 5. During normal operation, DISC5 is high impedance. During a fault condition or power-down, DISC5 provides an 85mA sink current. -- 26 OUT5 Open-Drain Output 5. When the voltage at SET4 is above 0.5V, OUT5 goes high impedance. OUT5 requires an external pullup resistor and can be pulled up to 13.2V. -- 27 SET5 External Set Monitored Threshold 5. Monitor a voltage by setting the threshold with an external resistive divider. The SET5 threshold is 0.5V. -- -- EP Sequence Order Select Inputs. SEQ1, SEQ2, and SEQ3 allow the order of sequencing for each supply to be programmable (Table 1). Exposed Pad. EP is internally connected to GND. Connect EP to the GND plane for improved heat dissipation. Do not use EP as the only ground connection. _______________________________________________________________________________________ 7 MAX16050/MAX16051 Pin Description (continued) MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability Functional Diagram VCC MAX16050 MAX16051 INTERNAL VCC/UVLO CHARGE PUMP ABP OUT1-OUT4 (OUT1-OUT5) CP_OUT DISC1-DISC4 (DISC1-DISC5) COMP 250mV SET1-SET4 (SET1-SET5) COMP 85mA RESET VREF CONTROL LOGIC OV_OUT FAULT EN COMP REM EN_HOLD SEQ1-SEQ3 (MAX16050 ONLY) ( ) ARE FOR MAX16051 ONLY. 8 GND ABP ABP TIMEOUT DELAY _______________________________________________________________________________________ Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability MAX16050/MAX16051 VTH_EN EN SHDN tDELAY VTH VTH_PL V1 tDELAY VTH V2 tDELAY VTH V3 tDELAY V4 VTH tRP RESET REM Figure 1. Sequencing Timing Diagram with Reverse Order Power-Down Using SHDN _______________________________________________________________________________________ 9 MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability VTH_EN VTH_EN EN SHDN tDELAY VTH VTH_PL V1 tDELAY VTH V2 tDELAY VTH V3 tDELAY VTH V4 tRP RESET REM Figure 2. Sequencing Timing Diagram with Simultaneous Order Power-Down Using EN 10 ______________________________________________________________________________________ Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability MAX16050/MAX16051 tFAULT-PW FAULT tDELAY V1 VTH_PL V2 V3 VTH_PL V4 RESET REM Figure 3. Sequencing Timing Diagram During a System Fault ______________________________________________________________________________________ 11 MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability ... PART DOES NOT RESPOND TO EN FALLING ... UNTIL EN_HOLD GOES HIGH EN EN_HOLD CONNECTED TO REM OF THE SECOND IC V1 V2 V3 V4 Figure 4. Power-Down Characteristics when REM of the Second IC is Connected to EN_HOLD of the First IC 12 ______________________________________________________________________________________ Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability combinations (Table 1). In the default mode (SEQ1 = SEQ2 = SEQ3 = High Impedance), the power-up sequence is OUT1OUT2OUT3OUT4. The MAX16051 features an additional channel and the sequence order is fixed at OUT1OUT2OUT3 OUT4OUT5. For complex systems with a large number of power supplies, the MAX16050/MAX16051 can be used in a daisy-chain configuration. Reverse sequencing in the daisy-chained configuration is still possible. The MAX16050/MAX16051 keep all OUT_ low (all of the supplies in the off-state) until four conditions are met. 1) The voltage at ABP exceeds the undervoltage lockout threshold. 2) The voltage at the analog enable input (EN) is above its threshold. 3) The shutdown input, SHDN, is not asserted. 4) All DISC_ voltages must be below 250mV. The MAX16050 monitors up to 5 voltages (Figure 5) with the ability to sequence up to 4 voltages, while the MAX16051 monitors up to 6 voltages with the ability to sequence up to 5 voltages. These devices control system power-up and power-down in a particular sequence order. The MAX16050/MAX16051 turn off all supplies and assert a reset to the processor when any of the voltages falls below its respective threshold. The MAX16050/MAX16051 offer an 85mA pulldown feature that helps discharge the output capacitance of DC-DC converters to ensure timely power-down. In addition, the MAX16050/MAX16051 also reverse sequence, monitoring each power-supply output voltage present at the associated DISC_ input and ensuring that the voltage falls below 250mV before turning off the next supply. The MAX16050 provides three sequence logic inputs, which select the sequence order from 24 possible VBUS V1 DC-DC EN V2 DC-DC EN V3 DC-DC EN V4 DC-DC EN DISC4 SET4 OUT4 DISC3 SET3 OUT3 DISC2 SET2 OUT2 DISC1 SET1 OUT1 VPU VCC RESET OV_OUT EN MAX16050 FAULT REM DELAY TIMEOUT ABP EN_HOLD SEQ3 SEQ2 SHDN SEQ1 OFF CP_OUT GND ON Figure 5. Typical Connection for Sequencing Four DC-DC Converters ______________________________________________________________________________________ 13 MAX16050/MAX16051 Detailed Description MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability When all of these conditions are met, the device starts the power-sequencing process by turning on OUT1-OUT_ in the sequence order. The sequence delay between each OUT_ is the time required for the power-supply voltage to exceed the undervoltage threshold plus the additional time delay set by the external delay capacitor; if no capacitor is connected to the sequence delay timing input (DELAY), only a short propagation delay (10s) occurs. As each voltage meets its respective threshold, the next OUT_ in the sequence goes high impedance (open-drain output), allowing the next power supply to turn on, which is then monitored by the next input stage. When all of the voltages exceed their respective thresholds, the reset output (RESET) deasserts after a reset timeout period to allow the system controller to start operating. After sequencing is complete, if any SET_ input drops below its threshold, a fault is detected. All power supplies are simultaneously turned off by the OUT_ outputs asserting low, the RESET output asserting, the DISC_ current pulldown turning on, and the FAULT output pulling low for at least 1.9s. The MAX16050/MAX16051 will then be ready to power on again. Sequencing begins as soon as the four startup conditions are met. Sequencing The MAX16050 features three three-state sequence logic inputs that select one of the 24 possible sequence orders (Table 1). These inputs allow the sequence order to be changed even after the board layout is finalized. The MAX16051 offers five channels and the device powers up in a fixed order from OUT1 to OUT5. Table 1. MAX16050 Sequencing Table Logic 14 SEQUENCE ORDER SEQ1 SEQ2 SEQ3 High-Z High-Z High-Z High-Z High-Z Low OUT1 OUT2 OUT4 OUT3 High-Z High-Z High OUT1 OUT3 OUT2 OUT4 High-Z Low High-Z OUT1 OUT3 OUT4 OUT2 High-Z Low Low OUT1 OUT4 OUT2 OUT3 FIRST SUPPLY SECOND SUPPLY THIRD SUPPY FOURTH SUPPLY OUT1 OUT2 OUT3 OUT4 High-Z Low High OUT1 OUT4 OUT3 OUT2 High-Z High High-Z OUT2 OUT1 OUT3 OUT4 High-Z High Low OUT2 OUT1 OUT4 OUT3 High-Z High High OUT2 OUT3 OUT1 OUT4 Low High-Z High-Z OUT2 OUT3 OUT4 OUT1 Low High-Z Low OUT2 OUT4 OUT1 OUT3 Low High-Z High OUT2 OUT4 OUT3 OUT1 Low Low High-Z OUT3 OUT1 OUT2 OUT4 Low Low Low OUT3 OUT1 OUT4 OUT2 Low Low High OUT3 OUT2 OUT1 OUT4 Low High High-Z OUT3 OUT2 OUT4 OUT1 Low High Low OUT3 OUT4 OUT1 OUT2 Low High High OUT3 OUT4 OUT2 OUT1 High High-Z High-Z OUT4 OUT1 OUT2 OUT3 High High-Z Low OUT4 OUT1 OUT3 OUT2 High High-Z High OUT4 OUT2 OUT1 OUT3 High Low High-Z OUT4 OUT2 OUT3 OUT1 High Low Low OUT4 OUT3 OUT1 OUT2 High Low High OUT4 OUT3 OUT2 OUT1 ______________________________________________________________________________________ Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability Disabling Channels If any channel is not used, connect the associated SET_ input to ABP. Connect DISC_ of the disabled channel to GND or leave it unconnected. The channel exclusion feature adds more flexibility to the device in a variety of different applications. SHDN and EN Inputs The shutdown input (SHDN) initiates a reverse sequencing event. When SHDN is brought low, the device will sequentially power down in reverse order. During this period, all DISC_ inputs are monitored to make sure the voltage of each supply falls below 250mV before allowing the next supply to shut down. The next OUT_ goes low as soon as the previous DISC_ input drops below 250mV without any capacitor-adjusted delay. This continues until all supplies are turned off. SHDN is internally pulled up to ABP. When EN falls below its threshold, the device performs a simultaneous power-down and does not reverse sequence. When either SHDN or EN initializes the power-down event, the reset output (RESET) immediately asserts. At the end of the power-down event, when all DISC_ voltages are below 250mV, the bus removal output (REM) goes high impedance. Reset Output (RESET) The MAX16050/MAX16051 include a reset output. RESET is an open-drain output and requires an external pullup resistor. When any of the monitored voltages falls below its threshold, SHDN is pulled low, EN falls below its threshold, or FAULT is pulled low, RESET asserts and stays asserted for at least the minimum reset timeout period after all of these conditions are removed. Connect a capacitor from TIMEOUT to GND to adjust the reset timeout period. Connect TIMEOUT to ABP for the fixed timeout of 128ms (typ). Leave TIMEOUT unconnected for a 10s (typ) timeout period. FAULT Input/Output The FAULT input/output asserts to signal a fault if any of the SET_ monitored voltages falls below its threshold while EN = SHDN = high. FAULT is internally pulled up to ABP by a 100k resistor. FAULT also can be used as an input. Pull FAULT low to simultaneously shut down the OUT_ outputs . For multichip solutions, all of the FAULT input/outputs can be connected together. In case of a fault condition, all outputs on every device are turned off and the internal pulldown circuitry is activated simultaneously. Overvoltage Fault Output (OV_OUT) The MAX16050/MAX16051 include an overvoltage fault output. OV_OUT is an open-drain output and requires an external pullup resistor. When any of the SET_ voltages exceed their 0.55V overvoltage threshold, OV_OUT goes low. When all of the SET_ voltages are below their overvoltage threshold, OV_OUT goes high impedance after a short propagation delay. Discharge Inputs (DISC_) The discharge inputs (DISC_) discharge power-supply capacitors during a power-down or fault event and monitor power-supply output voltages during reverse sequencing. When an OUT_ output goes low, the associated DISC_ activates an 85mA pulldown current to discharge any output capacitors. This helps the power-supply output drop below the 250mV level so the next power supply can be turned off. During normal operation, DISC_ is high impedance and will not load the circuit. Bus Removal Output (REM) The MAX16050/MAX16051 include an open-drain bus removal output (REM) that indicates when it is safe to disconnect the input power after a controlled powerdown operation. REM monitors DISC_ voltages and goes low when any DISC_ input voltage goes above the DISC_ power low threshold (VTH_PL). REM goes high when all DISC_ inputs are below the DISC_ power low threshold (VTH_PL). For a visual signal of when it is unsafe to remove a powered board from the bus, connect an LED to REM. ______________________________________________________________________________________ 15 MAX16050/MAX16051 Charge-Pump Output (CP_OUT) The MAX16050/MAX16051 feature an on-chip charge pump that drives its output voltage to 5V above VCC, and it can be used as a pullup voltage to drive one or more external n-channel MOSFETs (see the Typical Operating Circuit). The charge-pump output can be modeled as a 25A current source with a compliance voltage of (VCC + 5V); the slew rate can be controlled by connecting a capacitor from the gate of the MOSFET to ground. When using CP_OUT to provide the pullup voltage for multiple MOSFETs, ensure that the voltage is enough to enhance a MOSFET despite the load of the other pullup resistors (which may be connected to outputs that are deasserted low). MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability Enable Hold Input (EN_HOLD) When EN_HOLD is low, a high-to-low transition on SHDN or on EN is ignored. EN_HOLD must be high for SHDN or EN to disable the device. This feature is used when multiple MAX16050/MAX16051s are daisychained (see Figure 7). Connect EN_HOLD to ABP if not used. Delay Time Input (DELAY) Connect a capacitor (CDELAY) between DELAY and GND to adjust the sequencing delay period (tDELAY) that occurs between sequenced channels. Use the following formula to estimate the delay: tDELAY = 10s + (500k x CDELAY) equation to estimate the value of the resistors based on the amount of acceptable error: e x V1TH R1 = A ISET where eA is the fraction of the maximum acceptable absolute resistive divider error attributable to the input leakage current (use 0.01 for 1%), V1TH is the powergood threshold for the power supply being monitored, and ISET is the worst-case SET_ input leakage current (see the Electrical Characteristics table). Calculate R2 as follows: where tDELAY is in seconds and CDELAY is in Farads. Leave DELAY unconnected for the default 10s (typ) delay. R2 = VTH x R1 V1TH - VTH Reset Timeout Input (TIMEOUT) Pullup Resistor Values Connect a capacitor (C TIMEOUT ) from TIMEOUT to GND to set the reset timeout period. After all SET_ inputs exceed their thresholds (VTH), RESET remains low for the programmed timeout period, tRP, before deasserting (see Figure 1). Use the following formula to estimate the reset timeout period: tRP = 10s + (500k x CTIMEOUT) where tRP is in seconds and CTIMEOUT is in Farads. Leave TIMEOUT unconnected for the default 10s (typ) timeout delay or connect TIMEOUT to ABP to enable a fixed 128ms (typ) timeout. The exact value of the pullup resistors for the opendrain outputs is not critical, but some consideration should be made to ensure the proper logic levels when the device is sinking current. For example, if VCC = 3.3V and the pullup voltage is 5V, keep the sink current less than 3.2mA as shown in the Electrical Characteristics table. As a result, the pullup resistor should be greater than 1.6k. For a 13.2V pullup, the resistor should be larger than 4.1k. Extra care must be taken when using CP_OUT as the pullup voltage. If multiple pullup resistors are connected to CP_OUT and one or more of the connected OUT_ outputs are asserted, the current drawn can drop the CP_OUT voltage enough to prevent an enabled MOSFET from turning on completely. Applications Information Resistor Value Selection The MAX16050/MAX16051 feature four and five SET_ inputs, respectively, and the threshold voltage (VTH) at each SET_ input is 0.5V (typ). To monitor a voltage V1TH, connect a resistive divider network to the circuit as shown in Figure 6, and use the following equation to calculate the monitored threshold voltage: R1 V1TH = VTH x 1 + R2 Balance accuracy and power dissipation when choosing the external resistors. The input to the voltage monitor is a high-impedance input with a small 100nA leakage current. This leakage current contributes to the overall error of the threshold voltage, and this error is proportional to the value of the resistors used to set the threshold. Small-valued resistors reduce the error but increase the power consumption. Use the following 16 V1TH VBUS R1 VCC SET_ RESET R2 MAX16050 MAX16051 GND Figure 6. Setting the SET_ Input ______________________________________________________________________________________ Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability MOSFET Selection The external pass MOSFET connects in series with the sequenced power-supply source. Since the load current and the MOSFET drain-to-source impedance (RDSON) determine the voltage drop, the on-characteristics of the MOSFET affect the load supply accuracy. For highest supply accuracy and lowest voltage drop, select a MOSFET with an appropriate drain-to-source on-resistance with a gate-to-source bias of 4.5V to 6.0V (see Table 2). In Figure 7, SHDN is pulled low to initiate the powerdown sequence. When all of the supply voltages monitored by U2 are off, the bus removal output (REM) goes high, thereby allowing U1 to start sequencing down. REM normally is at a logic-low state when all voltages are good. Connect U2's REM to U1's EN_HOLD to force U1 to stay on even if EN and SHDN are pulled low. This enable-and-hold circuitry allows the system to power down correctly. Layout and Bypassing For better noise immunity, bypass VCC to GND with a 0.1F capacitor installed as close to the device as possible. Bypass ABP to GND with a 1F capacitor installed as close to the device as possible; ABP is an internally generated voltage and must not be used to supply more than 1mA to external circuitry. Connect the exposed pad (EP) to the ground plane for improved heat dissipation. Do not use EP as the only ground connection for the device. Table 2. Recommended MOSFETs MANUFACTURER Fairchild Vishay PART VDS (V) VGSth (V) RDSON AT VGS = 4.5V (m) IMAX AT 50mV VOLTAGE DROP (A) Qg (nC) (TYP) FOOTPRINT FDC633N 30 0.67 42 1.19 11 Super SOT-6 FDP8030L FDB8030L 30 1.5 4.5 11.11 120 TO-220 TO-263AB FDD6672A 30 1.2 9.5 5.26 33 TO-252 FDS8876 30 2.5 (max) 17 2.94 15 SO-8 Si7136DP 20 3 4.5 11.11 24.5 SO-8 Si4872DY 30 1 10 5 27 SO-8 SUD50N02-09P 20 3 17 2.94 10.5 TO-252 Si1488DH 20 0.95 49 1.02 6 SOT-363 SC70-6 IRL3716 20 3 4.8 10.4 53 TO220AB D2PAK TO-262 IRL3402 20 0.7 10 5 78 (max) TO-220AB IRL3715Z 20 2.1 15.5 3.22 7 TO220AB D2PAK TO-262 IRLML2502 20 1.2 45 1.11 8 SOT23-3 Micro3 International Rectifier ______________________________________________________________________________________ 17 MAX16050/MAX16051 Daisy-Chaining the MAX16050/MAX16051 The MAX16050/MAX16051 can be daisy-chained to sequence and monitor a large number of voltages (Figure 7). When a fault occurs on any of the monitored inputs, FAULT goes low, signaling a fast power-down. Connect all FAULT pins of the MAX16050/MAX16051 together to ensure that all power supplies are turned off during a fault. VBUS VBUS EN PULL SHDN LOW TO INITIATE A REVERSE ORDER SHUTDOWN OF ALL 8 SUPPLIES Figure 7. Daisy-Chaining Two Devices to Sequence Up to 8 Voltages 18 ______________________________________________________________________________________ SET4 FAULT DELAY TIMEOUT EN_HOLD OV_OUT SEQ3 ABP MAX16050 SEQ1 FAULT RESET U2 REM GND DISC4 OUT4 SET3 DISC3 SET2 DISC2 OUT2 SET1 DISC1 CP_OUT VCC OV_OUT DELAY SEQ3 SEQ2 SEQ1 REM SHDN ABP TIMEOUT MAX16050 GND OUT1 DISC4 SET4 RESET U1 V8 DC-DC EN SHDN EN EN_HOLD OUT4 DISC3 SET3 OUT3 DISC2 SET2 OUT2 SET1 DISC1 CP_OUT V7 DC-DC EN V4 DC-DC EN VCC V6 DC-DC EN V3 DC-DC EN OUT3 V2 DC-DC EN V5 DC-DC EN SEQ2 V1 DC-DC EN OUT1 MAX16050/MAX16051 Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability VPU Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability VBUS V4 V1 DC-DC EN V2 DC-DC EN V3 VPU DISC4 SET4 OUT4 DISC3 SET3 OUT3 DISC2 SET2 OUT2 DISC1 SET1 OUT1 DC-DC EN CP_OUT VCC EN RESET MAX16050 OV_OUT GND DELAY TIMEOUT ABP SEQ3 SEQ2 SHDN SEQ1 ON OFF EN_HOLD FAULT REM ______________________________________________________________________________________ 19 MAX16050/MAX16051 Typical Operating Circuit Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability MAX16050/MAX16051 Pin Configurations (continued) Chip Information OUT1 DISC1 REM 20 OV_OUT RESET 21 SET1 FAULT PROCESS: BiCMOS TOP VIEW 19 18 17 16 15 SHDN 22 14 EN_HOLD DELAY 23 13 DISC2 TIMEOUT 24 12 OUT2 DISC5 25 11 SET2 PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 10 DISC3 28 TQFN T2844-1 21-0139 9 OUT3 8 SET3 MAX16051 OUT5 26 SET5 27 *EP + 1 2 3 4 5 6 7 VCC GND ABP EN SET4 OUT4 DISC4 CP_OUT 28 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. THIN QFN (4mm x 4mm) *EP = EXPOSED PAD 20 ______________________________________________________________________________________ Voltage Monitors/Sequencer Circuits with Reverse-Sequencing Capability REVISION NUMBER REVISION DATE 0 11/07 Initial release 1 7/08 Revised Electrical Characteristics and Disabling Channels sections. DESCRIPTION PAGES CHANGED -- 2, 3, 15 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 21 (c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. MAX16050/MAX16051 Revision History