BL2553 The BL2553 is a load switch which provides full protection to systems and loads which may encounter large current conditions. BL2553 offers a 95mΩ current‐limited switch which can operate over an input voltage range of 2.5‐5.5V. The current limit can be externally programmed by a precision resistor, ranges from 75mA to 1.4A. Switch control is by a logic input (EN) capable of interfacing directly with low voltage control signals. Current is prevented from flowing when the switch is off and the output voltage is higher than the input voltage. BL2553 also features thermal shutdown protection which shuts off the switch to prevent damage to the part when a continuous over‐current condition causes excessive heating. When the switch current reaches the current limit, the parts operate in a constant‐current mode to prohibit excessive currents from causing damage. The BL2553 will not turn off after a current limit fault, but will rather remain in the constant current mode indefinitely. The nFAULT output asserts low during over‐current and reverse‐voltage conditions. BL2553 is housed in a tiny DFN2x2‐6L package 1 USB ports/Hubs Hot Swaps Cellphones Tablet PC Set Top Box PC motherboard Handheld Devices Up to 1.4A Max Load current Accurate Current‐limit threshold: +/‐5% Programmable Current‐limit : 75mA to 1.4A Fast Over‐Current Response Fault Flag Output: nFAULT Pin Reversed Current blocking Thermal Shutdown, UVLO protection Tiny DFN2x2‐6L 、SOT23‐6 Package (Note: Exceeding these limits may damage the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.) IN to GND…..............................................–0.3V to 6V OUT, ILIM, nFAULT, EN to GND…..–0.3V to VIN+0.3V OUT to GND Current …………………..Internally limited Maximum Power Dissipation………….…………...1.0W Operating Temperature Range …….…. –40°C to 85°C Storage Temperature Range….………–55°C to 150°C DFN2X2-6L o (VIN = 5V, unless otherwise specified. Typical values are at TA = 25 C.) PARAMETER Input Voltage Range Input UVLO Input Supply Current Input Shutdown Current CONDITIONS Rising, Hysteresis=25mV RILIM=20K ISW =500mA Power Switch On Resistance ISW =500mA, ‐40°C≤TJ≤120°C RILIM=18.7K Current limit Threshold RILIM=20K RILIM=49.9K Response time to Short‐circuit Reverse‐voltage Threshold VOUT‐VIN Reverse Leakage Current VOUT=5.5V,Vin=0V,VEN=High EN Input Logic High threshold VnFAULT=5.5V EN Input Logic Low threshold nFAULT Output Low Voltage InFAULT =1mA nFAULT Output Leakage De‐assertion due to Over‐current nFAULT Deglitch Time De‐assertion due to Reverse‐Voltage Thermal Shutdown Thermal Shutdown In Current Limit Thermal Shutdown Hysteresis MIN 2.5 0.66 TYP 2.35 120 0.5 95 1.395 1.295 0.520 1 150 0.5 70 9 4.5 160 135 MAX 5.5 1.5 145 2 1 170 1 15 UNITS V V μA μA mΩ mΩ A A A μS mV μA V V mV μA mS o o o C C C BL2553 NFD2X2‐6 PIN SOT23‐6 SOT23‐5 OUT 1 6 5 Current limit Output. Bypass with a capacitor that is greater than 120μF if used for USB ILIM 2 5 4 Current limit threshold setting pin. Connect a resistor from this pin to GND to set different current limit values nFAULT 3 4 EN GND IN 3 2 1 3 2 1 NAME 4 5 6 DESCRIPTION Fault flagging pin. Connect a pull up resistor to IN, when in fault conditions, this pin is asserted low Enable pin Ground Power input. Bypass with a 4.7μF capacitor to GND The BL2553 is a load switch which provides full protection to systems and loads which may encounter large current conditions. BL2553 offers a 95mΩ current‐limited switch which can operate over an input voltage range of 2.5‐5.5V. The current limit can be externally programmed by a precision resistor, ranges from 75mA to 1.4A. BL2553 also features reverse voltage blocking, UVLO, and thermal shutdown to protect IC from overheating. An nFAULT flag output provides a pull‐down signal to indicate fault conditions. CURRENT LIMITING The current limit ensures that the current through the switch doesn't exceed a maximum value while not limiting at less than a minimum value. The current at which the parts will limit is adjustable through the selection of an external resistor connected to ILIM. Information for selecting the resistor is found in the Application Info section. BL2553 thermal cycles if an overload condition is present long enough to activate thermal limiting in any of the above cases. The device turns off when the junction temperature exceeds 135°C (typ) while in current limit. The device remains off until the junction temperature cools 10°C (typ) and then restarts REVERSE‐VOLTAGE BLOCKING The reverse‐voltage protection feature turns off the Power MOSFET whenever the output voltage exceeds the input voltage by 150mV (typ) for 4‐ms (typ). This prevents damage to devices on 3 the input side of the BL2553 by preventing significant current from sinking into the input capacitance. The BL2553 allow the power MOSFET to turn on once the output voltage goes below the input voltage for the same 4‐ms deglitch time. The reverse‐voltage condition also asserts the nFAULT output (active‐low) after 4‐ms. During “OFF” condition, the reverse‐voltage blocking function is still in effect, preventing any current floating from OUT to IN even when the device is not in use. nFAULT FLAG The FAULT open‐drain output is asserted (active low) during an overcurrent, over temperature or reverse‐voltage condition. The BL2553 asserts the FAULT signal until the fault condition is removed and the device resumes normal operation. The nFAULT signal is de‐asserted once device power is cycled or the enable is toggled and the device resumes normal operation. The BL2553 and BL2553is designed to eliminate false nFAULT reporting by using an internal delay "deglitch" circuit for overcurrent (9‐ms typ) and reverse‐voltage (4.5‐ms typ) conditions without the need for external circuitry. This ensures that nFAULT is not accidentally asserted due to normal operation such as starting into a heavy capacitive load. The deglitching circuitry delays entering and leaving fault conditions. Over temperature conditions are not deglitched and assert the nFAULT signal immediately. Turn on Delay and Rise time VIN=5V, RILIM=20K, ROUT=5Ω CH1: Output Voltage; CH2: Enabled pin Voltage; CH4: Input Current Device Enabled into short‐Circuit VIN=5V, RILIM=20K, ROUT=0Ω CH2: Enabled pin Voltage; CH4: Input Current Turn off Delay and Fall Time VIN=5V, RILIM=20K, ROUT=5Ω CH1: Output Voltage; CH2: Enabled pin Voltage; CH4: Input Current Device Enabled into short‐Circuit VIN=5V, RILIM=20K, ROUT=0Ω CH2: Enabled pin Voltage; CH4: Input Current BL2553 Full Load to Short‐Circuit Short‐Circuit to Full load VIN=5V, RILIM=20K VIN=5V, RILIM=20K CH1: Output Voltage; CH2: nFault pin Voltage; CH4: Input Current CH1: Output Voltage; CH2: nFault pin Voltage; CH4: Input Current Short‐Circuit to No‐load VIN=5V,RILIM=20K No‐load to Short‐Circuit VIN=5V, RILIM=20K CH1: Output Voltage; CH2: nFAULT pin Voltage; CH4: Input Current No‐load to 1 Ω‐load VIN=5V,RILIM=20K CH1: Output Voltage; CH2: nFAULT pin Voltage CH4: Input Current 5 CH1: Output Voltage; CH2: nFAULT pin Voltage; CH4: Input Current 1 Ω‐load to No‐load VIN=5V,RILIM=20K CH1: Output Voltage; CH2: nFAULT pin Voltage CH4: Input Current BL2553 Input Voltage from 0V into 5V Input Voltage from 5V into 0V VOUT=5V, RILIM=20K, ROUT=10Ω CH1: Output Voltage; CH2: nFAULT pin Voltage CH3: Input Voltage; CH4: Input Current VOUT=5V, RILIM=20K, ROUT=10Ω CH1: Output Voltage; CH2: nFAULT pin Voltage CH3: Input Voltage; CH4: Input Current Switch current VS Drain‐Source Voltage Switch current VS Drain‐Source Voltage 1400 300 1200 250 Ids(mA) Ids(mA) 1000 800 600 200 150 100 400 200 50 Vin=5V,Rset=20K Vin=5V,Rset=100K 0 0 0 200 400 600 800 1000 Vin‐Vout(mV) 0 200 400 600 Vin‐Vout(mV) 800 1000 Switch current VS Drain‐Source Voltage 160 140 Ids(mA) 120 100 80 60 40 20 Vin=5V,Rset=200K 0 0 500 1000 1500 Vin‐Vout(mV) 6 BL2553 INPUT OUTPUT CAPACITANCE Input and output capacitance improves the performance of the device; the actual capacitance should be optimized for the particular application. For all applications, a 4.7µF or greater ceramic bypass capacitor between IN and GND is recommended as close to the device as possible for local noise de‐coupling. This precaution reduces ringing on the input due to power‐supply transients. Additional input capacitance may be needed on the input to reduce voltage overshoot from exceeding the absolute maximum voltage of the device during heavy transient conditions. This is especially important during bench testing when long, inductive cables are used to connect the evaluation board to the bench power‐supply. Placing a high‐value electrolytic capacitor on the output pin is recommended when large transient currents are expected on the output. SETTING THE CURRENT LIMIT THRESHOLD Typical Current Limit (mA) RILIM (KΩ) 200 138 180 152 151 179 100 266 82 324 68 389 51 520 43 612 30 873 20 1295 18.7 1395 Rlimt(K)=1.3A×20K/Itarget POWER DISSIPATION During normal operation as a switch, the power dissipated in the part will depend upon the level at which the current limit is set. The maximum allowed setting for the current limit is 1A and this will result in a power dissipation of, P = (ILIM)2 x RDS = (1)2 x 0.10 = 100mW If the part goes into current limit the maximum power dissipation will occur when the output is shorted to ground. This is more power than the package can dissipate, but the thermal shutdown of the part will activate to protect the part from damage due to excessive heating. A short on the output will cause the part to operate in a constant current state dissipating a worst case power of, P(max) = VIN(max) x ILIM(max) = 5.5 x 1 = 5W This large amount of power will activate the thermal shutdown and the part will cycle in and out of thermal shutdown so long as the ON pin is active and the short is present. 7 BL2553 DFN2X2-6L SOT23-6 8 BL2553 SOT23-5 9