MIC2546-2BM

MIC2546/2547 Dual Programable Current Limit Switch General Description Features The MIC2546 and MIC2547 are integrated high-side dual • 2.7V to 5.5V input power switches optimized for low loss dc power switching • Adjustable current-limit up to 1.5A and other power management applications, including • Reverse current flow blocking (no “body diode”) Advanced Configuration and Power Interface (ACPI). The • 100μA typical on-state supply current per channel MIC2546/47 is a cost-effective, highly integrated solution • 2μA typical off-state supply current that requires few external components to satisfy USB and ACPI requirements. • 120mΩ maximum on-resistance Load current management features include a precision • Open-drain fault flag resistor-programmable output current-limit and a soft-start • Thermal shutdown circuit which minimizes inrush current when the switch is • Thermal shutdown output latch (MIC2547) enabled. Thermal shutdown, along with current-limit, • 2ms (slow) turn-on and fast turnoff protects theswitch and the attached device. • Available with active-high or active-low enable The MIC2546/47’s open-drain flag outputs are used to indicate current-limiting or thermal shutdown to a local controller. The MIC2547 has an additional internal latch Applications which turns the output off upon thermal shutdown providing robust fault control. The enable signal is • USB power distribution compatible with both 3V and 5V logic, and is also used as • PCI Bus Power Switching the thermal shutdown latch reset for the MIC2547. • Notebook PC The MIC2546 and MIC2547 are available in active-high • ACPI power distribution and active-low enable versions in 16-pin TSSOP and SOP • PC card hot swap applications packages. • Inrush current-limiting Data sheets and support documentation can be found on • Ideal for dual supply applications Micrel’s web site at www.micrel.com. ___________________________________________________________________________________________________________ Typical Application Typical Advanced Configuration and Power Interface (ACPI) Application UL Recognized Component Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com January 2008 M9999-012508-A Micrel, Inc. MIC2546/2547 Ordering Information Part Number Standard Pb-Free Enable Latch (1) Junction Temp. Range(1) Package –40° to +85°C 16-pin SOP MIC2546-1BM MIC2546-1YM Active High MIC2546-1BTS MIC2546-1YTS Active High –40° to +85°C 16-pin TSSOP MIC2546-2BM MIC2546-2YM Active Low –40° to +85°C 16-pin SOP MIC2546-2BTS MIC2546-2YTS Active Low –40° to +85°C 16-pin TSSOP MIC2547-1BM MIC2547-1YM Active High –40° to +85°C 16-pin SOP MIC2547-1BTS MIC2547-1YTS Active High –40° to +85°C 16-pin TSSOP MIC2547-2BM MIC2547-2YM Active Low –40° to +85°C 16-pin SOP MIC2547-2BTS MIC2547-2YTS Active Low –40° to +85°C 16-pin TSSOP • • • • Note: 1. Thermal Shutdown Latch. Pin Configuration MIC2546/2547 (ENA) (FLGA) LOGIC, CHARGE PUMP (ILIMA) (ENB) (FLGB) LOGIC, CHARGE PUMP (OUTA) (INA) (OUTB) (INB) (ILIMB) (GND) Function Pinout 16-Pin SOP (M) 16-Pin TSSOP (TS) January 2008 2 M9999-012508-A Micrel, Inc. MIC2546/2547 Pin Description Pin Number Pin Name 1 INA 2, 16 OUTA Switch A (Output): Output A MOSFET source. Pins 2 and 16 must be externally connected. 3 ENA Enable A (Input): Logic-compatible enable input. Active- activelow (–2). High input >1.7V typical; low input VIN) when the switch is disabled. In this situation, the MIC2546/47 avoids undesirable current flow from OUTX to INX. Both OUT pins for a given channel must be connected together. ⎛ 230V RSETX = ⎜⎜ ⎝ ILIMITX where: 154Ω < RSET < 2.29kΩ For example, to set a 1A nominal current-limit, RSET is calculated as: ⎛ 230V ⎞ ⎜ ⎟ = 230Ω ⎝ 1A ⎠ Current through RSETX increases with OUT current. The voltage across RSETX could be monitored with a high impedance comparator to provide an indication of output current. RSETX should be between 154Ω and 2.29kΩ (0.5% resistor value). Thermal Shutdown Thermal shutdown shuts off the output MOSFET and signals the fault flag if the die temperature exceeds 140°C. 10°C of hysteresis prevents the switch from turning on until the die temperature drops to 130°C. Overtemperature detection functions only when the switch is enabled. The MIC2547 features an internal latch which causes the part to remain off after thermal shutdown until a reset pulse is provided via the enable pin. While in currentlimit, the thermal shutdown latch prevents on/off cycling of the output. Refer to Figure 2 for timing diagram. The flag remains low until reset. Short-Circuit Protection In the event of a short-circuit, the output current will fold back to approximately 80% of the short-circuit currentlimit. Fault Flag FLGX is an N-channel, open-drain MOSFET output. The fault-flag is active (low) for current-limit or thermal shutdown conditions. The flag output MOSFET is capable of sinking a 10mA load to typically 100mV above ground. Enable Input ENX must be driven logic high or logic low, or be pulled high or low for a clearly defined input. Floating the input may cause unpredictable operation. ENX should not be allowed to go negative with respect to GND, and VENX should be less than or equal to VINX. January 2008 ⎞ ⎟⎟ ⎠ 12 M9999-012508-A Micrel, Inc. MIC2546/2547 TJ = PD × θJA + TA where: Application Information Supply Filtering A 0.1μF to 1μF bypass capacitor from INX to GND, located near the MIC2546 and MIC2547, 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 transients must not exceed the absolute maximum supply voltage (VIN max = 6V) even for a short duration. TJ = junction temperature TA = ambient temperature θJA = is the thermal resistance of the package Transient Overcurrent Filter The inrush current from the connection of a heavy capacitive load may cause the fault flag to fall for 10μs to 200μs while the switch is in a constant-current mode, charging the capacitance. Adding an optional series resistor-capacitor (RSET2) in parallel with RSET, as shown in Figure 3, allows the transient current-limit to be set to a different value than steady state. A typical USB hot-plug inrush is 2A to 3A for 10μs to 20μs. If RSET is 435Ω (510mA), an RSET2 of 88Ω (2.5A) and CSET of μF (RC = 100μs) allows transient surge of 3A to pass for 100μs without tripping the overcurrent flag (FLG). USB Power Distribution The MIC2546 is ideal for meeting USB power distribution requirements. Figure 3 depicts a USB Host application. RSET should be set to a value providing a current-limit >500mA. The accurate current-limit of the MIC2546 will reduce power supply current requirements. Also, fast reaction to short circuit faults prevent voltage droop in mobile PC applications. Supply Bypassing 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 and junction temperature are found below. Calculation of power dissipation can be accomplished by the following equation: PD = RDS(ON) × (IOUT)2 To relate this to junction temperature, the following equation can be used: January 2008 Printed Circuit Board Hot-Plug The MIC2546/47 are ideal inrush current-limiters suitable for hot-plug applications. Due to the integrated charge pump, the MIC2546/47 presents a high impedance when off and slowly becomes a low impedance as it turns on. This “softstart” feature effectively isolates power supplies from highly capacitive loads by reducing inrush current during hot-plug events. 13 M9999-012508-A Micrel, Inc. MIC2546/2547 Figure 3. USB Host Application January 2008 14 M9999-012508-A Micrel, Inc. MIC2546/2547 Package Information 16-Pin SOP (M) 16-Pin TSSOP (TS) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2001 Micrel, Incorporated. January 2008 15 M9999-012508-A