MIC2027/2077 Micrel MIC2027/2077 Quad USB Power Distribution Switch Preliminary Information General Description Features The MIC2027 and MIC2077 are quad high-side MOSFET switches optimized for general-purpose power distribution requiring circuit protection. The MIC2027/77 are internally current limited and have thermal shutdown that protects the device and load. The MIC2077 offers “smart” thermal shutdown that reduces current consumption in fault modes. When a thermal shutdown fault occurs, the output is latched off until the faulty load is removed. Removing the load or toggling the enable input will reset the device output. Both devices employ soft-start circuitry that minimizes inrush current in applications where highly capacitive loads are employed. A fault status output flag is asserted during overcurrent and thermal shutdown conditions. Transient current limit faults are internally filtered. The MIC2027/77 is available in narrow (150 mil) and wide (300 mil) SOP (small outline packages). • • • • • • • • • • • • 140mΩ maximum on-resistance per channel 2.7V to 5.5V operating range 500mA minimum continuous current per channel Short-circuit protection with thermal shutdown Thermally isolated channels Fault status flag with 3ms filter eliminates false assertions Undervoltage lockout Reverse current flow blocking (no “body diode”) Circuit breaker mode (MIC2077) reduces power consumption Logic-compatible inputs Soft-start circuit Low quiescent current Pin-compatible with MIC2524 and MIC2527 Applications • • • • • • USB peripherals General purpose power switching ACPI power distribution Notebook PCs PDAs PC card hot swap Typical Application 5V ± 3% Ferrite Bead VBUS 10k MIC5203-3.3 LDO Regulator IN 4.7 µF 3.3V USB Controller V+ OUT 1µF MIC2027 ON/OFF ENA OVERCURRENT GND D– GND 0.01µF IN FLGA ENB IN OUTA FLGB OUTB OUTC ENC D+ FLGC OUTD END GND GND FLGD D+ 33µF* D– GND 0.1 µF Downstream USB Port 1 500mA max. VBUS D+ 33µF* 0.01µF D– GND Downstream USB Port 2 500mA max. VBUS Bold lines indicate 0.1" wide, 1-oz. copper high-current traces. D+ 33µF* 0.01µF D– GND * 33µF, 16V tantalum or 100µF, 10V electrolytic per port Downstream USB Port 3 500mA max. VBUS D+ 33µF* 0.01µF D– GND Downstream USB Port 4 500mA max. 4-Port Self-Powered Hub Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com June 2000 1 MIC2027/2077 MIC2027/2077 Micrel Ordering Information Part Number Enable Temperature Range Package MIC2027-1BWM Active High –40°C to +85°C 16-lead wide SOP MIC2027-1BM Active High –40°C to +85°C 16-lead SOP MIC2027-2BWM Active Low –40°C to +85°C 16-lead wide SOP MIC2027-2BM Active Low –40°C to +85°C 16-lead SOP MIC2077-1BWM Active High –40°C to +85°C 16-lead wide SOP MIC2077-1BM Active High –40°C to +85°C 16-lead SOP MIC2077-2BWM Active Low –40°C to +85°C 16-lead wide SOP MIC2077-2BM Active Low –40°C to +85°C 16-lead SOP Pin Configuration FLGA 1 16 FLGB ENA 2 15 ENB OUTA 3 14 OUTB GND 4 13 IN(A/B) IN(C/D) 5 12 GND OUTC 6 11 OUTD ENC 7 10 END FLGC 8 9 3 OUTA ENA 2 FLGA 1 LOGIC, CHARGE PUMP ENB 15 FLGB 16 LOGIC, CHARGE PUMP 13 IN(A/B) 14 OUTB 6 OUTC ENC 7 FLGC 8 LOGIC, CHARGE PUMP END 10 FLGD 9 LOGIC, CHARGE PUMP 5 IN(C/D) 11 OUTD FLGD 4 GND 12 16-Lead SOP (M) 16-Lead Wide SOP (WM) MIC2027/2077 Functional Pinout 2 June 2000 MIC2027/2077 Micrel Pin Description Pin Number Pin Name Pin Function 1 FLGA Fault Flag A: (Output): Active-low, open-drain output. Low indicates overcurrent or thermal shutdown conditions. Overcurrent conditions must last longer than tD to assert flag. 2 ENA Switch A Enable (Input): Logic-compatible enable input. Active high (-1) or active low (-2). 3 OUTA Switch A Output 4, 12 GND Ground 5 IN(C/D) Input: Channel C and D switch and logic supply input. 6 OUTC Switch C Output 7 ENC Switch C Enable (Input) 8 FLGC Fault Flag C (Output) 9 FLGD Fault Flag D (Output) 10 END Switch D Enable (Input) 11 OUTD Switch D Output 13 IN(A/B) Supply Input: Channel A and B switch and logic supply input. 14 OUTB Switch B Output 15 ENB Switch B Enable (Input) 16 FLGB Fault Flag B (Output) Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Supply Voltage (VIN) ...................................... –0.3V to +6V Fault Flag Voltage (VFLG) .............................................. +6V Fault Flag Current (IFLG) ............................................ 25mA Output Voltage (VOUT) .................................................. +6V Output Current (IOUT) ............................... Internally Limited Enable Input (IEN) .................................... –0.3V to VIN + 3V Storage Temperature (TS) ...................... –65°C to +150 °C Lead Temperature (soldering 5 sec.) ........................ 260°C ESD Rating, Note 3 ...................................................... 1kV Supply Voltage (VIN) ................................... +2.7V to +5.5V Ambient Temperature (TA) ......................... –40°C to +85°C Junction Temperature Range (TJ) ........... Internally Limited Thermal Resistance [300 mil] Wide SOP (θJA) .................................. 120°C/W [150 mil] SOP (θJA) ........................................... 112°C/W DIP(θJA) ............................................................. 130°C/W June 2000 3 MIC2027/2077 MIC2027/2077 Micrel Electrical Characteristics VIN = +5V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted Symbol Parameter Condition IDD Supply Current VEN Enable Input Threshold Min Typ Max Units MIC20x7-1, VENA–D ≤ 0.8V (switch off), OUT = open 1.5 10 µA MIC20x7-2, VENA–D ≥ 2.4V (switch off), OUT = open 1.5 10 µA MIC20x7-1, VENA–D ≥ 2.4V (switch on), OUT = open 200 320 µA MIC20x7-2, VENA–D ≤ 0.8V (switch on), OUT = open 200 320 µA low-to-high transition 1.7 2.4 V high-to-low transition 0.8 Enable Input Hysteresis IEN Enable Input Current VEN = 0V to 5.5V –1 Enable Input Capacitance RDS(on) Switch Resistance 1.45 V 250 mV 0.01 µA 1 1 pF VIN = 5V, IOUT = 500mA 100 150 mΩ VIN = 3.3V, IOUT = 500mA 110 170 mΩ 10 µA Output Leakage Current MIC20x7-1, VENx ≤ 0.8V; MIC20x7-2, VENx ≥ 2.4V, (output off) Output Current in Latched Thermal Shutdown MIC2077 (per Latch Output) (during thermal shutdown state) 50 tON Output Turn-On Delay RL = 10Ω, CL = 1µF, see “Timing Diagrams” 1.3 5 ms tR Output Turn-On Rise Time RL = 10Ω, CL = 1µF, see “Timing Diagrams” 1.15 4.9 ms tOFF Output Turnoff Delay RL = 10Ω, CL = 1µF, see “Timing Diagrams” 35 100 µs tF Output Turnoff Fall Time RL = 10Ω, CL = 1µF, see “Timing Diagrams” 32 100 µs ILIMIT Short-Circuit Output Current VOUT = 0V, enabled into short-circuit 0.9 1.25 A Current-Limit Threshold ramped load applied to output 1.0 1.25 A Short-Circuit Response Time VOUT = 0V to IOUT = ILIMIT (short applied to output) 20 Overcurrent Flag Response Delay VIN = 5V, apply VOUT = 0V until FLG low tD Undervoltage Lockout Threshold Error Flag Output Resistance Error Flag Off Current Overtemperature Threshold Note 4 0.5 1.5 VIN = 3.3V, apply VOUT = 0V until FLG low 3 µA µs 7 ms 3 ms VIN rising 2.2 2.4 2.7 V VIN falling 2.0 2.15 2.5 V IL = 10mA, VIN = 5V 10 25 Ω IL = 10mA, VIN = 3.3V 15 40 Ω 10 µA VFLAG = 5V TJ increasing, each switch 140 °C TJ decreasing, each switch 120 °C TJ increasing, both switches 160 °C TJ decreasing, both switches 150 °C Note 1. Exceeding the absolute maximum rating may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. Note 4. If there is an output current limit fault on one channel, that channel will shut down when the die reaches approximately 140°C. If the die reaches approximately 160°C, the other channel driven by the same input will shut down, even if neither channel is in current limit. MIC2027/2077 4 June 2000 MIC2027/2077 Micrel Test Circuit VOUT Device Under OUT Test RL CL Timing Diagrams tR tF 90% VOUT 90% 10% 10% Output Rise and Fall Times VEN 50% tOFF tON 90% VOUT 10% Active-Low Switch Delay Times (MIC20x7-2) VEN 50% tOFF tON VOUT 90% 10% Active-High Switch Delay Times (MIC20x7-1) June 2000 5 MIC2027/2077 MIC2027/2077 Micrel Supply On-Current vs. Temperature On-Resistance vs. Temperature 300 140 200 150 3.3V 100 50 4 100 5V 80 60 IOUT = 500mA 40 RL=10Ω CL=1µF 3 2 VIN = 3.3V 1 20 VIN = 5V 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Supply On-Current vs. Input Voltage On-Resistance vs. Input Voltage Turn-Off Rise Time vs. Input Voltage 200 300 RESISTANCE (mΩ) 400 CURRENT (µA) 3.3V 120 -40°C 200 +25°C +85°C 100 2.5 2.0 150 RISE TIME (ms) CURRENT (µA) 5V 250 5 RISE TIME (ms) 160 ON-RESISTANCE (mΩ) 350 Turn-On Rise Time vs. Temperature +85°C +25°C 100 -40°C 50 +85°C 1.5 1.0 +25°C -40°C 0.5 RL=10Ω CL=1µF IOUT = 500mA VIN = 3.3V 600 VIN = 5V 400 200 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Short-Circuit Current-Limit vs. Input Voltage 800 CURRENT LIMIT (mA) 700 600 500 +85°C +25°C -40°C 400 300 200 100 0 2.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) MIC2027/2077 5.5 0 2.5 5.5 Current-Limit Threshold vs. Temperature 1200 1200 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 5.5 Fall Time vs. Temperature 400 VIN = 5V 1000 800 FALL TIME (µs) CURRENT LIMIT (mA) 1000 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) VIN = 3.3V 600 400 300 VIN = 3.3V 200 RL=10Ω CL=1µF 100 200 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Current-Limit Threshold vs. Input Voltage Fall Time vs. Input Voltage 300 1000 800 250 +85°C +25°C RISE TIME (µs) Short-Circuit Current-Limit vs. Temperature 800 0 2.5 5.5 CURRENT LIMIT THRESHOLD (mA) 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) CURRENT LIMIT THRESHOLD (mA) 0 2.5 -40°C 600 400 200 0 2.5 200 150 100 50 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 6 5.5 0 2.5 TA = 25°C CL = 1µF RL = 10Ω 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 5.5 June 2000 MIC2027/2077 Micrel Enable Threshold vs. Temperature Flag Delay vs. Temperature VEN RISING DELAY TIME (ms) 2.0 1.5 VEN FALLING 1.0 0.5 SUPPLY CURRENT (µA) VIN = 3.3V 4 VIN = 5V 3 2 1 VIN = 5V 0.30 5V 0.25 0.20 0.15 0.10 3.3V 0.05 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Enable Threshold vs. Input Voltage Flag Delay vs. Input Voltage Supply Off Current vs. Input Voltage 2.0 5 VEN RISING 1.5 1.0 VEN FALLING 0.5 4 3 0.35 +85°C SUPPLY CURRENT (µA) 2.5 ENABLE THRESHOLD (V) 0.35 5 DELAY TIME (ms) ENABLE THRESHOLD (V) 2.5 Supply Off Current vs. Temperature +25°C -40°C 2 1 TA = 25°C 0 2.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 0 2.5 5.5 3.0 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 5.5 0.30 +85°C 0.25 0.20 0.15 0.10 +25°C -40°C 0.05 0 2.5 3.0 3.5 4.0 4.5 VOLTAGE (V) 5.0 5.5 UVLO Threshold vs. Temperature UVLO THRESHOLD (V) 3.0 2.5 VIN RISING 2.0 VIN FALLING 1.5 1.0 0.5 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) June 2000 7 MIC2027/2077 MIC2027/2077 Micrel Functional Characteristics UVLO—VIN Falling (MIC2027-1) VFLG VIN (2V/div.) (2V/div.) VIN VFLG (2V/div.) (2V/div.) UVLO—VIN Rising (MIC2027-1) TIME (100ms/div.) Turn-On/Turnoff (MIC2027-1) Turn-On (MIC2027-1) 712mA (Inrush Current) VIN = 5V CL = 147µF RL = 35Ω IOUT (200mA/div.) VIN = 5V CL = 147µF RL = 35Ω IOUT (200mA/div.) VEN = VIN CL = 57µF RL = 35Ω TIME (10ms/div.) VOUT VFLG VEN (5V/div.) (5V/div.) (10V/div.) VEN VOUT VFLG (5V/div.) (5V/div.) (10V/div.) IOUT (100mA/div.) VEN = VIN CL = 57µF RL = 35Ω 140mA 140mA TIME (10ms/div.) TIME (500µs/div.) Turnoff (MIC2027-1) Enabled Into Short (MIC2027-1) VEN VOUT VFLG (5V/div.) (5V/div.) (10V/div.) VEN VOUT VFLG (5V/div.) (5V/div.) (10V/div.) 2.2V VOUT IOUT (100mA/div.) (5V/div.) VOUT (2V/div.) 2.4V 3.1ms (tD) IOUT (500mA/div.) IOUT (200mA/div.) 700mA VIN = 5V CL = 147µF RL = 35Ω 140mA TIME (500µs/div.) TIME (5ms/div.) MIC2027/2077 VIN = 5V 8 June 2000 MIC2027/2077 Micrel Current-Limit Response (Ramped Load–MIC2027-1) CL = 110µF IOUT (200mA/div.) CL = 210µF VOUT (5V/div.) VFLG VIN (10V/div.) (10V/div.) VEN VFLG (5V/div.) (10V/div.) Inrush Current Response (MIC2027-1) VIN = 5V RL = 31Ω IOUT (500mA/div.) CL = 310µF CL = 10µF Short Removed Thermal Shutdown Hysteresis Current-Limit Response (MIC2027-1) VEN VFLG (5V/div.) (10V/div.) Current-Limit Response (Stepped Short—MIC2027-1) VOUT (5V/div.) VIN = 5V CL = 47µF RL = stepped short IOUT (5A/div.) VOUT (5V/div.) 800mA VIN = 5V CL = 0 RL = stepped short Short-Circuit (800mA) TIME (1ms/div.) TIME (50µs/div.) Independent Thermal Shutdown (MIC2027-1) Independent Thermal Shutdown (MIC2027-1) VENA VFLGB VFLGA (5V/div.) (5V/div.) (10V/div.) IOUT (2A/div.) VENB VFLGA (5V/div.) (10V/div.) Short-Circuit Current (800mA) Thermal Shutdown TIME (100ms/div.) VOUTA = No Load (No Thermal Shutdown) IOUTA (500mA/div.) VFLGB (5V/div.) IOUTB (500mA/div.) Current-Limit Threshold (1A) TIME (1ms/div.) Thermal Shutdown VENA = 5V VENB = 5V VENC = 0V VEND = 0V TIME (100ms/div.) June 2000 VIN = 5V CL = 47µF VOUTB = No Load (No Thermal Shutdown) Thermal Shutdown VENA = 5V VENB = 5V VENC = 0V VEND = 0V TIME (100ms/div.) 9 MIC2027/2077 MIC2027/2077 Micrel No Load Load Removed Enable Reset VFLG (5V/div.) VOUT VFLG (5V/div.) (10V/div.) RL = 0 IOUTB (500mV/div.) VOUT (5V/div.) VIN = 5V CL = 47µF VENB = 0V Output Reset Ramp Load to Short CL = 57µF RL = 35Ω IOUT (500mA/div.) Output Reset Thermal Shutdown Thermal Shutdown VIN = 5V TIME (2.5s/div.) TIME (100ms/div.) Thermal Shutdown (Output Reset by Removing Load—MIC2077-2) Independent Thermal Shutdown (MIC2077-2) Output Latched Off VFLGB VFLGA (5V/div.) (5V/div.) RL = 0 Load Removed (Output Reset) Ramp Load to Short Load Removed Output Reset Thermal Shutdown Thermal Shutdown VIN = 5V CL = 47µF No Load No Thermal Shutdown on Channel B IOUTA (500mA/div.) IOUT (500mA/div.) VOUT (5V/div.) VEN VFLG (5V/div.) (10V/div.) Thermal Shutdown (Output Reset by Toggling Enable—MIC2077-2) VEN (10V/div.) Thermal Shutdown (MIC2077-2—Output Latched Off) TIME (100ms/div.) VIN = 5V CL = 47µF VENB = 0V VENA = 0V VENC = 5V VEND = 5V TIME (2.5s/div.) Independent Thermal Shutdown (MIC2077-2) IOUTB (500mA/div.) VFLGA VFLGB (5V/div.) (10V/div.) RL = 0 Load Removed No Load Output Reset No Thermal Shutdown on Channel A Thermal Shutdown VIN = 5V CL = 47µF VENB = 0V VENA = 0V VENC = 5V VEND = 5V TIME (2.5s/div.) MIC2027/2077 10 June 2000 MIC2027/2077 Micrel Block Diagram RESET (MIC2077 ONLY) THERMAL SHUTDOWN LATCH FLGA FLAG DELAY CHARGE PUMP OUTA GATE CONTROL CURRENT LIMIT OSC. THERMAL SHUTDOWN UVLO 1.2V REFERENCE CHARGE PUMP GATE CONTROL IN (A/B) CURRENT LIMIT ENB FLAG DELAY RESET (MIC2077 ONLY) RESET (MIC2077 ONLY) OUTB THERMAL SHUTDOWN LATCH FLGB THERMAL SHUTDOWN LATCH FLGC FLAG DELAY OUTC ENC CHARGE PUMP GATE CONTROL CURRENT LIMIT OSC. THERMAL SHUTDOWN UVLO 1.2V REFERENCE CHARGE PUMP GATE CONTROL IN (C/D) CURRENT LIMIT END FLAG DELAY RESET (MIC2077 ONLY) MIC2027 OUTD FLGD THERMAL SHUTDOWN LATCH GND June 2000 11 MIC2027/2077 MIC2027/2077 Micrel where: TJ = junction temperature TA = ambient temperature θJA = is the thermal resistance of the package Current Sensing and Limiting The current-limit threshold is preset internally. The preset level prevents damage to the device and external load but still allows a minimum current of 500mA to be delivered to the load. The current-limit circuit senses a portion of the output MOSFET switch current. The current-sense resistor shown in the block diagram is virtual and has no voltage drop. The reaction to an overcurrent condition varies with three scenarios: Functional Description Input and Output IN is the power supply connection to the logic circuitry and the drain of the output MOSFET. OUT is the source of the output MOSFET. In a typical circuit, current flows from IN to OUT toward the load. If VOUT is greater than VIN, current will flow from OUT to IN, since the switch is bidirectional when enabled. The output MOSFET and driver circuitry are also designed to allow the MOSFET source to be externally forced to a higher voltage than the drain (VOUT > VIN) when the switch is disabled. In this situation, the MIC2027/77 prevents undesirable current flow from OUT to IN. Thermal Shutdown Thermal shutdown is employed to protect the device from damage should the die temperature exceed safe margins due mainly to short circuit faults. Each channel employs its own thermal sensor. Thermal shutdown shuts off the output MOSFET and asserts the FLG output if the die temperature reaches 140°C and the overheated channel is in current limit. The other channels are not effected. If however, the die temperature exceeds 160°C, all channels will be shut off. Upon determining a thermal shutdown condition, the MIC2077 will latch the output off and activate a pull-up current source. When the load is removed, this current source will pull the output up and reset the latch. Toggling EN will also reset the latch. The MIC2027 will automatically reset its output when the die temperature cools down to 120°C. The MIC2027 output and FLG signal will continue to cycle on and off until the device is disabled or the fault is removed. Figure 2 depicts typical timing. Depending on PCB layout, package, ambient temperature, etc., it may take several hundred milliseconds from the incidence of the fault to the output MOSFET being shut off. This time will be shortest in the case of a dead short on the output. Power Dissipation The device’s junction temperature depends on several factors such as the load, PCB layout, ambient temperature and package type. Equations that can be used to calculate power dissipation of each channel and junction temperature are found below. PD = RDS(on) × IOUT2 Total power dissipation of the device will be the summation of PD for all channels. To relate this to junction temperature, the following equation can be used: TJ = PD × θJA + TA MIC2027/2077 Switch Enabled into Short-Circuit If a switch is enabled into a heavy load or short-circuit, the switch immediately enters into a constant-current mode, limiting the output voltage. The FLG signal is asserted indicating an overcurrent condition. Short-Circuit Applied to Enabled Output When a heavy load or short-circuit is applied to an enabled switch, a large transient current may flow until the currentlimit circuitry responds. Once this occurs the device limits current to less than the short-circuit current limit specification. Current-Limit Response—Ramped Load The MIC2027/77 current-limit profile exhibits a small foldback effect of about 100mA. Once this current-limit threshold is exceeded the device switches into a constant current mode. It is important to note that the device will supply current up to the current-limit threshold. Fault Flag The FLG signal is an N-channel open-drain MOSFET output. FLG is asserted (active-low) when either an overcurrent or thermal shutdown condition occurs. In the case of an overcurrent condition, FLG will be asserted only after the flag response delay time, tD, has elapsed. This ensures that FLG is asserted only upon valid overcurrent conditions and that erroneous error reporting is eliminated. For example, false overcurrent conditions can occur during hot-plug events when a highly capacitive load is connected and causes a high transient inrush current that exceeds the current-limit threshold. The FLG response delay time tD is typically 3ms. Undervoltage Lockout Undervoltage lockout (UVLO) prevents the output MOSFET from turning on until VIN exceeds approximately 2.5V. Undervoltage detection functions only when the switch is enabled. 12 June 2000 MIC2027/2077 Micrel Load and Fault Removed (Output Reset) Short-Circuit Fault VEN VOUT ILIMIT ILOAD IOUT VFLG Thermal Shutdown Reached 3ms typ. delay Figure 1. MIC2077-2 Fault Timing: Output Reset by Removing Load Short-Circuit Fault VEN Load/Fault Removed VOUT ILIMIT ILOAD IOUT VFLG Thermal Shutdown Reached 3ms typ. delay Figure 2. MIC2027-2 Fault Timing June 2000 13 MIC2027/2077 MIC2027/2077 Micrel controller from responding to FLG being asserted, an external RC filter, as shown in Figure 3, can be used to filter out transient FLG assertion. The value of the RC time constant should be selected to match the length of the transient, less tD(min) of the MIC2027/77. Universal Serial Bus (USB) Power Distribution The MIC2027/77 is ideally suited for USB (Universal Serial Bus) power distribution applications. The USB specification defines power distribution for USB host systems such as PCs and USB hubs. Hubs can either be self-powered or buspowered (that is, powered from the bus). The requirement for USB self-powered hubs is that the port must supply a minimum of 500mA at an output voltage of 5V ±5%. In addition, the output power delivered must be limited to below 25VA. Upon an overcurrent condition, the host must also be notified. To support hot-plug events, the hub must have a minimum of 120µF of bulk capacitance, preferably low ESR electrolytic or tantulum. Please refer to Application Note 17 for more details on designing compliant USB hub and host systems. Applications Information Supply Filtering A 0.1µF to 1µF bypass capacitor positioned close to VIN and GND of the device is strongly recommended to control supply transients. Without a bypass capacitor, an output short may cause sufficient ringing on the input (from supply lead inductance) to damage internal control circuitry. Printed Circuit Board Hot-Plug The MIC2027/77 are ideal inrush current-limiters for hot-plug applications. Due to the integrated charge pump, the MIC2027/77 presents a high impedance when off and slowly becomes a low impedance as it turns on. This “soft-start” feature effectively isolates power supplies from highly capacitive loads by reducing inrush current. In cases of extremely large capacitive loads (>400µF), the length of the transient due to inrush current may exceed the delay provided by the integrated filter. Since this inrush current exceeds the current-limit flag delay specification, FLG will be asserted during this time. To prevent the logic V+ Logic Controller OVERCURRENT 10k R C MIC2027 1 2 3 4 5 6 7 8 FLGA FLGB ENA ENB OUTA OUTB GND IN(A/B) IN(C/D) GND OUTC OUTD ENC END FLGC FLGD 16 15 14 13 12 11 10 9 Figure 3. Transient Filter MIC2027/2077 14 June 2000 MIC2027/2077 Micrel Package Information PIN 1 0.157 (3.99) 0.150 (3.81) DIMENSIONS: INCHES (MM) 0.020 (0.51) REF 0.050 (1.27) BSC 0.0648 (1.646) 0.0434 (1.102) 0.020 (0.51) 0.013 (0.33) 0.0098 (0.249) 0.0040 (0.102) 0.394 (10.00) 0.386 (9.80) 45° 0°–8° 0.050 (1.27) 0.016 (0.40) SEATING PLANE 0.244 (6.20) 0.228 (5.79) 16-Lead SOP (M) PIN 1 DIMENSIONS: INCHES (MM) 0.301 (7.645) 0.297 (7.544) 0.027 (0.686) 0.031 (0.787) 0.094 (2.388) 0.090 (2.286) 0.297 (7.544) 0.293 (7.442) 0.103 (2.616) 0.050 (1.270) 0.016 (0.046) 0.099 (2.515) TYP TYP 0.409 (10.389) 0.405 (10.287) 7° TYP 0.015 R (0.381) 0.015 (0.381) SEATING MIN PLANE 0.330 (8.382) 0.326 (8.280) 0.022 (0.559) 0.018 (0.457) 5° TYP 10° TYP 0.032 (0.813) TYP 0.408 (10.363) 0.404 (10.262) 16-Lead Wide SOP (WM) June 2000 15 MIC2027/2077 MIC2027/2077 Micrel MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. © 2000 Micrel Incorporated MIC2027/2077 16 June 2000