STEF05 Electronic fuse for 5 V line Datasheet − production data Features ■ Continuous current (typ): 3.6 A ■ N-channel on-resistance (typ): 40 mΩ ■ Enable/Fault functions ■ Output clamp voltage (typ): 6.65 V ■ Undervoltage lockout ■ Short-circuit limit ■ Overload current limit ■ Controlled output voltage ramp ■ Thermal latch (typ): 165 °C ■ Uses tiny capacitors ■ Operating junction temp. - 40 °C to 125 °C ■ Available in DFN10 (3x3 mm) package DFN10 (3x3 mm) Applications ■ Hard disk drives ■ Solid state drives (SSD) ■ Hard disk and SSD arrays ■ Set-top boxes ■ DVD and Blu-ray disc drivers Description The STEF05 is an integrated electronic fuse optimized for monitoring output current and input voltage. Connected in series to a 5 V rail, it is capable of protecting the electronic circuitry on its output from overcurrent and overvoltage. The device has a controlled delay and turn-on time. When an overload condition occurs, the STEF05 limits the output current to a predefined safe value. If the anomalous overload condition Table 1. persists, it goes into an open state, disconnecting the load from the power supply. If a continuous short-circuit is present on the board, when power is re-applied the E-fuse initially limits the output current to a safe value, and then again goes into an open state. The device is equipped with a thermal protection circuit. The intervention of the thermal protection is signalled to the board monitoring circuits through a signal on the Fault pin. Unlike mechanical fuses, which must be physically replaced after a single event, the Efuse does not degrade in its performance after short-circuit/thermal protection interventions and it is reset either by recycling the supply voltage or using the Enable pin. The companion chip for 12 V power rails is also available with part number STEF12. Device summary Order code Package Packaging STEF05PUR DFN10 (3x3 mm) Tape and reel January 2013 This is information on a product in full production. Doc ID 019055 Rev 5 1/20 www.st.com 20 Contents STEF05 Contents 1 Device block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1 Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1.1 Turn-on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1.2 Normal operating condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1.3 Output voltage clamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1.4 Current limiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1.5 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.2 R limit calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.3 Cdv/dt calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.4 Enable/Fault pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2/20 Doc ID 019055 Rev 5 STEF05 Device block diagram 1 Device block diagram Figure 1. STEF05 block diagram AM09891v1 Doc ID 019055 Rev 5 3/20 Pin configuration 2 STEF05 Pin configuration Figure 2. Pin configuration (top view) Source Source Source Source Source GND dv/dt En/fault I-Limit N/C VCC AM09867v1 Table 2. Pin description Pin n° Symbol Note 1 to 5 VOUT/Source Connected to the source of the internal power MOSFET and to the output terminal of the fuse 6 NC 7 I-Limit A resistor between this pin and the Source pin sets the overload and short-circuit current limit levels. En/Fault The Enable/Fault pin is a tri-state, bi-directional interface. During normal operation the pin must be left floating, or it can be used to disable the output of the device by pulling it to ground using an open drain or open collector device. If a thermal fault occurs, the voltage on this pin goes into an intermediate state to signal a monitor circuit that the device is in thermal shutdown. It can be connected to another device of this family to cause a simultaneous shutdown during thermal events. 9 dv/dt The internal dv/dt circuit controls the slew rate of the output voltage at turn-on. The internal capacitor allows a ramp-up time of around 1 ms. An external capacitor can be added to this pin to increase the ramp time. If an additional capacitor is not required, this pin should be left open. 10 GND Ground pin 11 VCC Exposed pad. Positive input voltage must be connected to VCC. 8 4/20 Not connected Doc ID 019055 Rev 5 STEF05 Maximum ratings 3 Maximum ratings Table 3. Absolute maximum ratings Symbol Parameter VCC Value Positive power supply voltage (steady state) -0.3 to 10 Positive power supply voltage (max 100 ms) -0.3 to 15 Unit V VOUT/source (max 100 ms) -0.3 to Vcc+0.3 V I-Limit (max 100 ms) -0.3 to 15 V -0.3 to 7 V -0.3 to 7 V -40 to 125 °C -65 to 150 °C 260 °C En/Fault dv/dt Top Operating junction temperature range TSTG Storage temperature range TLEAD Lead temperature (soldering) 10 sec (1) 1. The thermal limit is set above the maximum thermal rating. It is not recommended to operate the device at temperatures greater than the maximum ratings for extended periods of time. Note: Absolute maximum ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Table 4. Thermal data Symbol Parameter Value Unit RthJA Thermal resistance junction-ambient 52.7 °C/W RthJC Thermal resistance junction-case 17.4 °C/W Test conditions Value Unit HBM 2 kV MM 150 V CDM 500 V Table 5. ESD performance Symbol ESD Parameter ESD protection Doc ID 019055 Rev 5 5/20 Electrical characteristics 4 STEF05 Electrical characteristics VCC = 5 V, VEN = 3.3 V, CI = 10 µF, CO = 47 µF, TJ = 25 °C (unless otherwise specified). Table 6. Electrical characteristics for the STEF05 Symbol Parameter Test conditions Min. Typ. Max. Unit Under/overvoltage protection VClamp Output clamping voltage VCC = 10 V 5.95 6.65 7.35 V VUVLO Undervoltage lockout Turn-on, voltage rising 3.2 3.6 4 V VHyst UVLO hysteresis 0.40 V 500 µs Power MOSFET tdly Delay time Enabling of chip to ID = 100 mA with a 1 A resistive load (1) RDSon On-resistance VOFF Off state output voltage -40 °C < TJ < 125 °C Continuous current in2 40 pad, TA = 25 °C 60 mΩ 70 VCC = 10 V, VGS = 0, RL = infinite 0.5 ID 20 (2) 35 (2) 100 mV 3.6 A Minimum copper, TA= 80 °C 1.7 Current limit IShort ILim Short-circuit current limit RLimit = 22 Ω Overload current limit RLimit = 22 Ω 1.9 2.9 3.9 2.9 A A dv/dt circuit dv/dt Enable to VOUT = 4.7 V, No Cdv/dt 0.7 1.2 2.5 ms Low level input voltage Output disabled 0.35 0.58 0.81 V Intermediate level input voltage Thermal fault, output disabled 0.82 1.4 1.95 V High level input voltage Output enabled 1.96 2.64 3.3 V 3.4 4.3 5.4 V -10 -30 µA Output voltage ramp time Enable/Fault VIL VI(INT) VIH VI(MAX) High state maximum voltage IIL Low level input current (sink) VEnable = 0 V II High level leakage current for external switch VEnable = 3.3 V 1 µA Maximum fan-out for fault signal Total numbers of chips that can be connected to this pin for simultaneous shutdown 3 Units Total device IBias 6/20 Device operational 0.5 Thermal shutdown 1 Bias current 2 mA Doc ID 019055 Rev 5 STEF05 Table 6. Electrical characteristics Electrical characteristics for the STEF05 (continued) Symbol Vmin Parameter Test conditions Min. Typ. Minimum operating voltage Max. Unit 3.1 V Thermal latch TSD (2) Shutdown temperature 165 °C 1. Pulse test: Pulse width = 300 µs, duty cycle = 2% 2. Guaranteed by design, but not tested in production Doc ID 019055 Rev 5 7/20 Typical application 5 STEF05 Typical application Figure 3. Application circuit AM09868v1 Figure 4. Typical HDD application circuit AM09869v1 5.1 Operating modes 5.1.1 Turn-on When the input voltage is applied, the Enable/Fault pin goes up to the high state, enabling the internal control circuitry. After an initial delay time of typically 500 µs, the output voltage is supplied with a slope defined by the internal dv/dt circuitry. If no additional capacitor is connected to dv/dt pin, the total time from the Enable signal going high and the output voltage reaching the nominal value is around 1 ms (refer to Figure 5, 15). 8/20 Doc ID 019055 Rev 5 STEF05 5.1.2 Typical application Normal operating condition The STEF05 E-fuse behaves like a mechanical fuse, buffering the circuitry on its output with the same voltage shown at its input, with a small voltage fall due to the N-channel MOSFET RDSOn. 5.1.3 Output voltage clamp This internal protection circuit clamps the output voltage to a maximum safe value, typically 6.65 V, if the input voltage exceeds this threshold. 5.1.4 Current limiting When an overload event occurs, the current limiting circuit reduces the conductivity of the power MOSFET, in order to clamp the output current at the value selected externally by means of the limiting resistor RLimit (Figure 3). 5.1.5 Thermal shutdown If the device temperature exceeds the thermal latch threshold, typically 165 °C, the thermal shutdown circuitry turns the power MOSFET off, thus disconnecting the load. The EN/Fault pin of the device is automatically set at an intermediate voltage, in order to signal the overtemperature event. In this condition the E-fuse can be reset either by cycling the supply voltage or by pulling down the EN pin below the Vil threshold and then releasing it. 5.2 R limit calculation As shown in Figure 3, the device uses an internal N-channel sense FET with a fixed ratio, to monitor the output current and limit it at the level set by the user. The RLimit value for achieving the requested current limitation can be estimated by using the following theoretical formula, together with the graph in Figure 13: Current limit vs. RLimit. Equation 1 65 R Limit = -------------I Short 5.3 Cdv/dt calculation Connecting a capacitor between the Cdv/dt pin and GND allows the modification of the output voltage ramp-up time. Given the desired time interval Δt during which the output voltage goes from zero to its maximum value, the capacitance to be added on the Cdv/dt pin can be calculated using the following theoretical formula: Equation 2 C dvdt = 50 × 10 – 9 Δt – 30 × 10 – 12 Where Cdv/dt is expressed in Farads and the time in seconds. Doc ID 019055 Rev 5 9/20 Typical application STEF05 The addition of an external Cdv/dt also influences the initial delay time, defined as the time between the Enable signal going high and the start of the VOUT slope (Figure 5). The contribution of the external capacitor to this time interval can be estimated by using the following theoretical formula: Equation 3 delay time = 500 × 10 –6 + 13.6 × 10 6 × C dvdt Figure 5. Delay time and VOUT ramp-up time AM09870v1 6 VOUT 5 V 4 delay time ramp-up time EN/Fault 3 2 1 0 Time 5.4 Enable/Fault pin The Enable/Fault pin has the dual function of controlling the output of the device and, at the same time, of providing information about the device status to the application. When it is used as a standard Enable pin, it should be connected to an external open-drain or open-collector device. In this case, when it is pulled at low logic level, it turns the output of the E-Fuse off. If this pin is left floating, since it has internal pull-up circuitry, the output of the E-Fuse is kept ON in normal operating conditions. In case of thermal fault, the pin is pulled to an intermediate state (Figure 6). This signal can be provided to a monitor circuit, informing it that a thermal shutdown has occurred, or it can be directly connected to the Enable/Fault pins of other STEFxx devices on the same application in order to achieve a simultaneous enable/disable feature. When a thermal fault occurs, the device can be reset either by cycling the supply voltage or by pulling down the Enable pin below the Vil threshold and then releasing it. 10/20 Doc ID 019055 Rev 5 STEF05 Typical application Figure 6. Enable/Fault pin status 5 Normal operating condition EN/Fault voltage [V] 4 3 2 Thermal fault condition 1 Off/Reset 0 time Doc ID 019055 Rev 5 AM09871v1 11/20 Typical performance characteristics 6 STEF05 Typical performance characteristics The following plots are referred to the typical application circuit and, unless otherwise noted, at TA = 25 °C. Figure 7. Clamping voltage vs. temperature Figure 8. AM09872v1 7.5 VCC = 10 V 7.3 4 7.1 3.9 6.9 3.8 6.7 3.7 Voltage (V) Voltage (V) UVLO voltage vs. temperature 6.5 6.3 AM09873v1 3.6 3.5 6.1 3.4 5.9 3.3 5.7 3.2 -40 5.5 -40 -25 0 25 55 85 125 -25 0 25 55 85 125 150 Temperature °C 150 Temperature °C Figure 9. UVLO hysteresis vs. temperature Figure 10. Off-state voltage vs. temperature VCC = 10 V, VGS = 0, RL = infinite 180 0.48 160 0.46 0.44 140 0.42 120 Voltage (mV) Hysteresis (V) AM09875v1 200 AM09874v1 0.5 0.4 0.38 0.36 100 80 60 0.34 40 0.32 20 0.3 -40 -25 0 25 55 85 125 0 150 -40 Temperature °C -25 0 25 55 85 125 150 Temperature °C Figure 11. Bias current (device operational) Figure 12. ON resistance vs. temperature AM09876v1 2 AM09877v1 80 VCC = 5 V, RLIMIT = 22 Ω, ILOAD = 1 A 1.8 70 1.6 1.4 RDSON (mΩ) Current (mA) 60 1.2 1 0.8 50 40 0.6 0.4 30 0.2 20 0 -40 -25 0 25 55 85 125 150 -40 12/20 -25 0 25 55 Temperature °C Temperature °C Doc ID 019055 Rev 5 85 125 150 STEF05 Typical performance characteristics Figure 13. Current limit vs. RLimit Figure 14. Thermal latch delay vs. power AM09879v1 AM09878v1 6.00 VCC = 5 V, T = 25 °C 100 ILIM Thermal Action Time (ms) Short Circuit Current Limit (A) 5.00 ISHORT 4.00 3.00 2.00 T = 25 °C T = 55 °C T = 85 °C 10 1.00 0.00 0 10 20 30 40 50 60 70 80 1 0 10 20 30 40 50 60 External Sense Resistor (Ω ) Power (W) Figure 15. VOUT ramp-up vs. Enable Figure 16. VOUT clamping VCC = 15 V, CIN = 10 µF, COUT = 100 µF, RLIMIT = 22 Ω, No Cdv/dt VCC = 15 V, CIN = 10 µF, COUT = 100 µF, RLIMIT = 22 Ω, No Cdv/dt Figure 17. Line transient Figure 18. Startup into output short-circuit VCC = from 5 to 15 V RLIMIT = 22 Ω; IOUT = 500 mA, TRISE = 100 µs VCC = 5 V, RLIMIT = 22 Ω, VOUT = Connected to GND Doc ID 019055 Rev 5 13/20 Typical performance characteristics STEF05 Figure 19. Thermal latch from 2 A load to short-circuit Figure 20. Startup into output short-circuit (fast rise) VCC = 5 V, RLIMIT = 22 Ω VCC = 5 V, RLIMIT = 22 Ω, VOUT = Connected to GND 14/20 Doc ID 019055 Rev 5 STEF05 7 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark. Table 7. DFN10L (3x3 mm.) mechanical data mm. Dim. A Min. Typ. Max. 0.80 0.90 1.00 0.02 0.05 0.65 0.80 A1 A2 0.55 A3 0.20 b 0.18 0.25 0.30 D 2.85 3.00 3.15 D2 2.20 E 2.85 E2 1.40 2.70 3.00 1.75 E3 0.230 E4 0.365 e 0.50 L 0.30 ddd 3.15 0.40 0.50 0.08 Doc ID 019055 Rev 5 15/20 Package mechanical data STEF05 Figure 21. DFN10L package outline 7426335_H 16/20 Doc ID 019055 Rev 5 STEF05 Package mechanical data Tape and reel QFNxx/DFNxx (3x3 mm) mechanical data mm. inch. Dim. Min. Typ. A Max. Min. Typ. 330 13.2 12.992 C 12.8 D 20.2 0.795 N 60 2.362 T 0.504 0.519 18.4 0.724 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 Doc ID 019055 Rev 5 Max. 17/20 Package mechanical data STEF05 Figure 22. DFN10L footprint - recommended data (dimensions in mm.) 7426335_H 18/20 Doc ID 019055 Rev 5 STEF05 8 Revision history Revision history Table 8. Document revision history Date Revision Changes 15-Jul-2011 1 Initial release. 08-Aug-2011 2 Modified definition for Top in Table 3: Absolute maximum ratings. 15-Dec-2011 3 Removed Vdv/dt and Idv/dt rows from dv/dt circuit Table 6 on page 6. 06-Mar-2012 4 Updated: package mechanical data Table 7 on page 15, Figure 21 on page 16 and Figure 22 on page 18. 14-Jan-2013 5 Updated: package mechanical data Table 7 on page 15 and Figure 21 on page 16. Doc ID 019055 Rev 5 19/20 STEF05 Please Read Carefully: Information in this document is provided solely in connection with ST products. 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