MIC2525 Micrel MIC2525 USB Power Control Switch Not Recommended for New Designs Refer to MIC2025 General Description Features The MIC2525 is an integrated high-side power switch, optimized for self-powered and bus-powered Universal Serial Bus (USB) applications. Few external components are necessary to satisfy USB requirements. The MIC2525 satisfies the following USB requirements: each switch channel supplies up to 500mA as required by USB downstream devices; the switch’s low on-resistance meets USB voltage drop requirements; fault current is limited to typically 750mA, well below the UL 25VA safety requirements; and a flag output is available to indicate fault conditions to the local USB controller. Soft start eliminates the momentary voltage drop on the upstream port that may occur when the switch is enabled in bus-powered applications. • • • • • • • • • • • • • • • Additional features include thermal shutdown to prevent catastrophic switch failure from high-current loads, undervoltage lockout (UVLO) to ensure that the device remains off unless there is a valid input voltage present, and 3.3V and 5V logic compatible enable inputs. The MIC2525 is a UL recognized component and is available in active-high and active-low versions in 8-pin DIP and SOIC packages. Compliant to USB specifications UL Recognized Component 3V to 5.5V input 500mA minimum continuous load current per port 140mΩ maximum on-resistance 1.25A maximum short circuit current limit Open-drain fault flag pins 110µA typical on-state supply current 1µA typical off-state supply current Output can be forced higher than input (off-state) Thermal shutdown 2.4V typical undervoltage lockout (UVLO) 1ms turn-on (soft-start) and fast turnoff Active-high or active-low enable versions 8-pin SOIC and DIP packages Applications • • • • USB hosts and self-powered hubs USB bus-powered hubs Hot plug-in power supplies Battery-charger circuits For new designs, please see the MIC2025/2075. Typical Application VCC 5.0V 4.50V to 5.25V Upstream VBUS 100mA max. VBUS 3.3V USB Controller MIC5207-3.3 IN D+ 1µF D– VIN OUT GND 100k 10k 3.3V 1µF ON/OFF OVERCURRENT GND GND Ferrite Beads MIC2525-2 EN FLG IN GND OUT NC VBUS OUT D+ D– 150µF USB Port GND NC 0.1µF Data Data Single-Port USB Self-Powered Hub UL Recognized Component Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com January 2000 1 MIC2525 MIC2525 Micrel Ordering Information Part Number Enable Temperature Range Package MIC2525-1BM Active High –40°C to +85°C 8-Pin SOIC MIC2525-2BM Active Low –40°C to +85°C 8-Pin SOIC MIC2525-1BN Active High –40°C to +85°C 8-pin DIP MIC2525-2BN Active Low –40°C to +85°C 8-pin DIP Pin Configuration MIC2525 EN 1 8 OUT FLG 2 7 IN GND 3 6 OUT NC 4 5 NC 8-Pin SOIC (M) 8-Pin DIP (N) MIC2525 (EN) 1 (FLG) 2 LOGIC, CHARGE PUMP 6, 8 (OUT) 7 (IN) 3 (GND) Pin Description Pin Number Pin Name 1 EN Enable (Input): Logic-compatible enable input. High input > 2.1V typical. Low input <1.9V typical (-1 active high, -2 active low). 2 FLG Fault Flag (Output): Active-low, open-drain output. Indicates overcurrent, UVLO and thermal shutdown. 3 GND Ground: Supply return. 4, 5 NC Not internally connected. (For pin compatibility with the MIC2505, connect pin 7 to pin 5 and leave pin 4 unconnected.) 7 IN Supply Input: Output MOSFET drain. Also supplies IC’s internal circuitry. Connect to positive supply. 6, 8 OUT MIC2525 Pin Function Switch Output: Output MOSFET source. Typically connect to switched side of load. 2 January 2000 MIC2525 Micrel Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Supply Voltage (VIN) ..................................................... +6V Fault Flag Voltage (VFLG) .............................................. +6V Fault Flag Current (IFLG) ............................................ 50mA Output Voltage (VOUT) .................................................. +6V Output Current (IOUT) ............................... Internally Limited Control Input (VEN) ......................................... –0.3V to 12V Storage Temperature (TS) ....................... –65°C to +150°C Lead Temperature (Soldering 5 sec.) ....................... 260°C ESD Rating, Note 3 ...................................................... 2kV Supply Voltage (VIN) ...................................... +3V to +5.5V Ambient Operating Temperature (TA) ........ –40°C to +85°C Thermal Resistance SOIC (θJA) ......................................................... 120°C/W DIP(θJA) ............................................................. 130°C/W Electrical Characteristics VIN = +5V; TA = 25°C; unless noted. Parameter Condition Supply Current Enable Input Threshold Enable Input Current Min Typ Max Units Note 4, switch off, OUT = open 0.75 5 µA Note 4, switch on, OUT = open 110 160 µA low-to-high transition 2.1 2.4 V high-to-low transition, Note 4 0.8 1.9 VEN = 0V to 5.5V –1 ±0.01 Enable Input Capacitance Switch Resistance V µA 1 1 pF VIN = 5V, IOUT = 500mA 100 140 mΩ VIN = 3.3V, IOUT = 500mA 140 180 mΩ Output Turn-On Delay RL = 10Ω each output 0.5 ms Output Turn-On Rise Time RL = 10Ω each output 1 ms Output Turnoff Delay RL = 10Ω each output 1 20 µs Output Turnoff Fall Time RL = 10Ω each output 1 20 µs Output Leakage Current output disabled 10 µA Continuous Load Current 0.5 Short-Circuit Current Limit enable into load, VOUT = 4.0V Current-Limit Threshold Overtemperature Shutdown Threshold Error Flag Output Resistance 0.5 A 0.75 1.25 A ramped load applied to enabled output, VOUT ≤ 4.0V, Note 5 1.6 2.2 A TJ increasing 135 °C TJ decreasing 125 °C VIN = 5V, IL = 10mA 10 25 Ω VIN = 3.3V, IL = 10mA 15 40 Ω 1 µA Error Flag Off Current VFLAG = 5V 0.01 UVLO Threshold VIN = increasing 2.5 V VIN = decreasing 2.3 V 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. Off is ≤ 0.8V and on is ≥ 2.4V for the MIC2525-1. Off is ≥ 2.4V and on is ≤ 0.8V for the MIC2525-2. The enable input has approximately 200mV of hysteresis. See control threshold charts. Note 5. See “Functional Characteristics: Current-Limit Response” photo. January 2000 3 MIC2525 MIC2525 Micrel Typical Characteristics VIN = 5V; TA = 25°C; one switch section; unless noted. ON-RESISTANCE (mΩ) 90 RL = 44Ω 120 100 RL = 44Ω 80 VIN = 5V T = 25°C 3.5 4.0 4.5 5 SUPPLY VOLTAGE (V) 60 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 5.5 On-State Supply Current vs. Supply Voltage 200 150 100 50 1.5 1.0 0.5 SWITCH OFF 0 2 4 SUPPLY VOLTAGE (V) 2 6 On-State Supply Current vs. Temperature 150 100 50 SWITCH ON 2.0 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 5 Output Rise Time vs. Temperature 1 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) MIC2525 TIME (ms) TIME (µs) 2 VCTL FALLING 2 3 4 SUPPLY VOLTAGE (V) 5 2.5 1.0 0.5 SWITCH OFF 0.6 1.5 Control Threshold vs. Temperature VEN RISING 2.0 VEN FALLING 1.5 VIN = 5V 1.0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) Output Fall Time vs. Temperature 2.0 0.8 Awaiting Full Characterization Data VCTL RISING Off-State Supply Current vs. Temperature 1.5 1.0 2.0 1.0 6 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 4 3 3 4 5 SUPPLY VOLTAGE (V) ENABLE VOLTAGE (V) 0 SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) 200 Control Threshold vs. Supply Voltage 2.5 SWITCH ON 0 VIN FALLING 2.0 Off-State Supply Current vs. Supply Voltage 2.0 SUPPLY CURRENT (µA) 250 VIN RISING 2.5 1.5 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) THRESHOLD VOLTAGE (V) Awaiting Full Characterization Data UVLO Threshold Voltage vs. Temperature 3.0 Current-Limit Threshold vs. Temperature 1.8 Awaiting Full Characterization Data 0.4 0.2 CURRENT (A) OUTPUT RESISTANCE (mΩ) 100 80 3.0 SUPPLY CURRENT (µA) Output On-Resistance vs. Temperature 140 THRESHOLD VOLTAGE (V) Output On-Resistance vs. Supply Voltage 110 CURRENT LIMIT THRESHOLD 1.6 1.4 SHORT CIRCUIT CURRENT LIMIT 1.2 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (°C) 4 1.0 -25 0 25 50 75 TEMPERATURE (°C) 100 January 2000 MIC2525 Micrel Functional Characteristics Turn-On, Turnoff Characteristics VEN VOUT VFLG (2V/div.) (5V/div.) (5V/div.) 2.6V (UVLO) Threshold VFLG VOUT IOUT (200mA/div.)(5V/div.) (2V/div.) VEN = VIN RL = 35Ω CL = 15µF 144mA IOUT (100mA/div.) VIN (2V/div.) Input Voltage Response RL = 35Ω CL = 10µF TIME (2.5ms/div.) Turn-On, Turnoff Characteristics Short Circuit Response (Short Applied to Output) VOUT (2V/div.) VOUT (2V/div.) VFLG (5V/div.) VEN VFLG (5V/div.) (5V/div.) TIME (100ns/div.) 1A Short Circuit Current Limit IOUT (1A/div.) IOUT (100mA/div.) 144mA RL = 35Ω CL = 150µF Thermal Shutdown TIME (500ms/div.) TIME (2.5ms/div.) VOUT IOUT (1A/div.) (2V/div.) VFLG (5V/div.) VEN (5V/div.) Short Circuit Response Enable into Short Circuit Thermal Shutdown 1.1A Short Circuit Current-Limiting TIME (250ms/div.) January 2000 5 MIC2525 MIC2525 Micrel Current-Limit Response (Ramped Load) VOUT (2V/div.) VFLG (5V/div.) VFLG (5V/div.) VOUT (5V/div.) Short Circuit Transient Response (Short Applied to Output) Current Limit Threshold 1A Current Limit 1A Current Limit IOUT (1A/div.) IOUT (1A/div.) 2.76A TIME (500µs/div.) TIME (1ms/div.) Test Circuit 5V 10k Ferrite Bead 0.1µF MIC2525 EN OUT FLG IN GND OUT NC IOUT CL RL ILOAD (for Current Limit Response) NC Functional Characteristics Test Circuit MIC2525 6 January 2000 MIC2525 Micrel Block Diagram EN OSC. THERMAL SHUTDOWN UVLO 1.2V REFERENCE CHARGE PUMP GATE CONTROL IN CURRENT LIMIT OUT FLG GND January 2000 7 MIC2525 MIC2525 Micrel Undervoltage Lockout UVLO (undervoltage lockout) prevents the output MOSFET from turning on until VIN exceeds approximately 2.5V. In the undervoltage state, the FLAG will be low. After the switch turns on, if the voltage drops below approximately 2.3V, UVLO shuts off the output MOSFET and signals fault flag. Undervoltage detection functions only when the switch is enabled. Current Sensing and Limiting The current-limit threshold is preset internally. The preset level prevents damage to the output MOSFET and external load but allows a minimum current of 0.5A through the output MOSFET. Functional Description The MIC2525-1 and MIC2525-2 are high-side switches with active-high and active-low enable inputs, respectively. Fault conditions turn off or inhibit turn-on of the output transistor, depending upon the type of fault, and activate the open-drain error flag transistor making it sink current to ground. Input and Output IN (input) is the power supply connection to the logic circuitry and the drain of the output MOSFET. OUT (output) is the source of the output MOSFET. In a typical circuit, current flows through the switch from IN to OUT toward the load. If VOUT is greater than VIN when the switch is enabled, current will flow from OUT to IN since the MOSFET is bidirectional when on. The current-limit circuit senses a portion of the output FET 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: 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 output is off. In this situation, the MIC2525 avoids undesirable current flow from OUT to IN. If VIN < 2.5V, UVLO disables the switch. Thermal Shutdown Thermal shutdown shuts off the output MOSFET and signals the fault flag if the die temperature exceeds 135°C. 10°C of hysteresis prevents the switch from turning on until the die temperature drops to 125°C. Overtemperature detection functions only when the switch is enabled. Current Limit Induced Thermal Shutdown Internal circuitry increases the output MOSFET on-resistance until the series combination of the MOSFET on-resistance and the load impedance limit current to typically 750mA. The increase in power dissipation, in most cases, will cause the MIC2525 to go into thermal shutdown. When this is undesirable, thermal shutdown can be avoided by externally responding to the fault and disabling the current limited channel before the shutdown temperature is reached. The delay between the flag indication of a current limit fault and thermal shutdown will vary with ambient temperature, board layout, and load impedance, but is typically several hundred milliseconds. The USB controller must therefore recognize a fault and disable the switch within this time. If the fault is not removed or the switch is not disabled within this time, then the device will enter into a thermal oscillation of about 2Hz. This does not cause any damage to the device. Refer to “Functional Characteristics: Thermal Shutdown Response.” MIC2525 Switch Enabled into Short Circuit If a switch is powered on or enabled into a heavy load or shortcircuit, the switch immediately goes into a constant-current mode, reducing the output voltage. The fault flag goes low until the load is reduced. See the “Functional Characteristics: Short Circuit Response, Enabled into Short Circuit” photo. Short Circuit Applied to Output When a heavy load is applied, a large transient current may flow until the current limit circuitry responds. Once this occurs, the device limits current to less than the short-circuit current limit specification. See the “Short Circuit Transient Response, Short Applied to Output” graph. Current-Limit Response The MIC2525 current-limit profile exhibits a small foldback effect of approximately 500mA. Once this current-limit threshold is exceeded the device enters constant-current mode. This constant current is specified as the short circuit current limit in the “Electrical Characteristics” table. It is important to note that the MIC2525 will deliver load current up to the current-limit threshold which is typically 1.6A. Refer to “Functional Characteristics: Current-Limit Response” photo for details. Fault Flag FLG is an N-channel, open-drain MOSFET output. The faultflag is active (low) for one or more of the following conditions: undervoltage (while 2V < VIN < 2.7), current limit, or thermal shutdown. The flag output MOSFET is capable of sinking a 10mA load to typically 100mV above ground. 8 January 2000 MIC2525 Micrel Enable Input EN must be driven logic high or logic low for a clearly defined input. Floating the input may cause unpredictable operation. EN should not be allowed to go negative with respect to GND. Soft Start The MIC2525 presents a high impedance when off, and slowly becomes a low impedance as it turns on. This reduces inrush current and related voltage drop that results from charging a capacitive load, satisfying the USB voltage droop requirements for bus-powered applications as shown in Figure 2. Applications Information Supply Filtering A 0.1µF to 1µF bypass capacitor from IN to GND, located at 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. Input or output transients must not exceed the absolute maximum supply voltage (VIN max = 6V) even for a short duration. 3V to 5.5V The soft start circuit shown in Figure 3 can be utilized to meet USB transient regulation specifications with large load capacitances (CBULK > 10uF). The MIC2525 will provide inrush current limiting for these applications. Transient Overcurrent Filter When the MIC2525 is enabled, large values of capacitance at the output of the device will cause inrush current to exceed the short circuit current-limit threshold of the device and assert the flag. The duration of this time will depend on the size of the output capacitance. Refer to the “Functional Characteristics” turn-on and turnoff behaviors for details. MIC2525 1 2 3 4 EN OUT FLG IN GND OUT NC NC 8 7 0.1µF to 1µF 6 5 Figure 1. Supply Bypassing USB Controller MIC2525-xBM 1 VBUS 2 3 USB Host 4.7 µF 4 EN OUT FLG IN GND OUT NC NC 8 7 CBULK 6 Capacitive Load 5 0.1µF GND Cable Cable Bus Powered Hub Downstream USB Device Figure 2. Soft-Start Application USB Controller MIC2525-2 1 VBUS 2 4.7 µF USB Hub 3 4 EN OUT FLG IN GND OUT NC NC 8 7 USB Function 6 5 CBULK GND Cable USB Peripheral Figure 3. Inrush Current-Limit Application January 2000 9 MIC2525 MIC2525 Micrel During the capacitance charging time, the device enters into constant-current mode. As the capacitance is charged, the current decreases below the short circuit current-limit threshold, and the flag will then be deasserted. In USB applications, it is required that output bulk capacitance is utilized to support hot-plug events. When the MIC2525 is enabled, the flag may go active for about 1ms due to inrush current exceeding the current-limit setpoint. Additionally, during hot-plug events, inrush currents may also cause the flag to go active for 30µs. Since these conditions are not valid overcurrent faults, the USB controller must ignore the flag during these events. To prevent this erroneous overcurrent reporting, a 1ms RC filter as shown in Figure 4 may be used. MIC2525 Alternatively, a 1ms debounce routine may be programmed into the USB logic controller, eliminating the need for the RC filter. V+ USB Controller MIC2525 10k 1 OVERCURRENT 10k 0.1 µF 2 3 4 EN OUT FLG IN GND OUT NC NC 8 7 6 5 Figure 4. Transient Filter 10 January 2000 MIC2525 Micrel Package Information 0.026 (0.65) MAX) PIN 1 0.157 (3.99) 0.150 (3.81) DIMENSIONS: INCHES (MM) 0.020 (0.51) 0.013 (0.33) 0.050 (1.27) TYP 0.064 (1.63) 0.045 (1.14) 45° 0.0098 (0.249) 0.0040 (0.102) 0.197 (5.0) 0.189 (4.8) 0°–8° 0.010 (0.25) 0.007 (0.18) 0.050 (1.27) 0.016 (0.40) SEATING PLANE 0.244 (6.20) 0.228 (5.79) 8-Pin SOP (M) PIN 1 DIMENSIONS: INCH (MM) 0.380 (9.65) 0.370 (9.40) 0.255 (6.48) 0.245 (6.22) 0.135 (3.43) 0.125 (3.18) 0.300 (7.62) 0.013 (0.330) 0.010 (0.254) 0.018 (0.57) 0.100 (2.54) 0.130 (3.30) 0.380 (9.65) 0.320 (8.13) 0.0375 (0.952) 8-Pin Plastic DIP (N) January 2000 11 MIC2525 MIC2525 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 MIC2525 12 January 2000