Positive High-Voltage, Hot-Swap Controller

Transcription

1 9-36; Rev 0; /0 EVALUATION KIT AVAILABLE Positive High-Voltage, Hot-Swap Controller General Description The is a fully integrated hot-swap controller for +9V to +80V positive supply rails. The allows for the safe insertion and removal of circuit cards into a live backplane without causing glitches on the backplane power-supply rail. This device is pin and function compatible to LT6-. The features a programmable foldback-current limit. If the device remains in current limit for more than a programmable time, the external n-channel MOSFET latches off. Other features include a programmable undervoltage lockout and a programmable output-voltage slew rate through an external n-channel MOSFET. The provides a power-good output () to indicate the status of the output voltage. For a variety of /, latch/autoretry-fault management, autoretry duty-cycle options, refer to the MAX5933 and MAX593 data sheets. The operates in the -0 C to +85 C extended temperature range. This device is available in an 8-pin SO package. Hot Board Insertion Electronic Circuit Breaker Industrial High-Side Switch/Circuit Breaker Network Routers and Switches V/8V Industrial/Alarm Systems Applications Features Pin and Function Compatible with LT6- Provides Safe Hot Swap for +9V to +80V Power Supplies Safe Board Insertion and Removal from Live Backplanes Active-High Power-Good Output () Programmable Foldback-Current Limiting High-Side Drive for an External N-Channel MOSFET Undervoltage Lockout (UVLO) Overvoltage Protection Latched Fault Management User-Programmable Supply Voltage Power-Up Rate Ordering Information PART TEMP RANGE PIN-PACKAGE ESA -0 C to +85 C 8 SO Pin Configuration TOP VIEW Typical Application Circuit appears at end of data sheet. ON 8 V CC SENSE 5 SO Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS (Voltages referenced to ) V CC V to +85V SENSE,, ON V to (V CC + 0.3V), V to +85V V to +95V Maximum Current...-50mA, +50mA Maximum Current into Any Other Pin...±50mA Continuous Power Dissipation (T A = +70 C) 8-Pin SO (derate 5.9mW/ C above +70 C)...70mW Operating Temperature Range...-0 C to +85 C Maximum Junction Temperature C Storage Temperature Range C to +50 C ESD Rating (Human Body Model)...000V Lead Temperature (soldering, 0s) C Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V CC = +V, = 0V, T A = -0 C to +85 C, unless otherwise noted. Typical values are at T A = +5 C.) (Note ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage Range V CC 9 80 V Supply Current I CC V ON = 3V, V CC = 80V. 3.5 ma V CC Undervoltage Lockout V LKO V CC low-to-high transition V V CC Undervoltage Lockout Hysteresis V LKOHYST 0. V High-Voltage Threshold V H low-to-high transition V Low-Voltage Threshold V L high-to-low transition V Hysteresis V HYST 80 mv Input Bias Current I IN V = 0V - + µa Threshold Line Regulation V 9V V CC 80V, ON = 0V, T A = 0 C to +70 C SENSE Trip Voltage (V CC - V SENSE ) V = 0V, T A = 0 C to +70 C 8 7 V SENSETRIP V = V, T A = 0 C to +70 C mv/v Pullup Current I UP Charge pump on, V = 7V µa Pulldown Current I DN Any fault condition, V = V ma V CC = 0.8V to 0V External N-Channel Gate Drive V V - V CC V CC = 0V to 80V Pullup Current I UP V = 0V µa Pulldown Current I ON V = V µa ON Logic-High Threshold V ONH ON low-to-high transition V ON Logic-Low Threshold V ONL ON high-to-low transition V ON Hysteresis V ONHYST 80 mv ON Input Bias Current I INON V ON = 0V - + µa Leakage Current I OH V = 80V 0 µa I O = ma 0. Output Low Voltage V OL I O = ma.5 SENSE Input Bias Current I SENSE V SENSE = 0V to V CC - +3 µa Thermal Shutdown Temperature rising 50 C Thermal Shutdown Hysteresis 0 C mv V V

3 ELECTRICAL CHARACTERISTICS (continued) (V CC = +V, = 0V, T A = -0 C to +85 C, unless otherwise noted. Typical values are at T A = +5 C.) (Note ) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS ON Low-to- Low Propagation Delay ON High-to- High Propagation Delay Low-to- Low Propagation Delay t PHLON C = 0, Figures, 6 µs t PLHON C = 0, Figures,.7 µs t PHL Figures, 3 3. µs High-to- High Propagation Delay (V CC - V SENSE ) High-to- Low Propagation Delay t PLH Figures, 3.5 µs t PHLSENSE T A = +5 C, C = 0, Figures, 0.5 µs Note : All currents into the device are positive and all currents out of the device are negative. All voltages are referenced to ground, unless noted otherwise. 3

4 ON V CC V SENSE Test Circuit and Timing Diagrams.33V.33V ON 5V t PLHON t PHLON 5kΩ 0nF 5V V Figure. Test Circuit Figure. ON to Timing.33V t PLH.33V t PHL V CC - SENSE 7mV t PHLSENSE V V V CC Figure 3. to Timing Figure. SENSE to Timing

5 (V CC = +8V, T A = +5 C, unless otherwise noted.) ICC (ma) T A = -0 C I CC vs. V CC T A = +5 C V CC (V) T A = +85 C toc0 ICC (ma) I CC vs. TEMPERATURE V CC = 8V V CC = V 0 Typical Operating Characteristics toc0 LOW-VOLTAGE THRESHOLD (V) LOW-VOLTAGE THRESHOLD vs. TEMPERATURE toc03 HIGH-VOLTAGE THRESHOLD (V) HIGH-VOLTAGE THRESHOLD vs. TEMPERATURE toc0 HYSTERESIS (V) HYSTERESIS vs. TEMPERATURE toc05 I PULLUP CURRENT (µa) I PULLUP CURRENT vs. TEMPERATURE toc DRIVE (V - VCC) (V) DRIVE vs. TEMPERATURE V CC = 8V V CC = 0.8V toc07 DRIVE (V - VCC) (V) DRIVE vs. V CC toc V CC (V) 5

6 Typical Operating Characteristics (continued) (V CC = +8V, T A = +5 C, unless otherwise noted.) PULLUP CURRENT (µa) PULLUP CURRENT vs. TEMPERATURE toc09 PULLUP CURRENT (µa) PULLUP CURRENT vs. V CC T A = +5 C T A = 0 C T A = +85 C T A = -0 C toc0 ON HIGH-VOLTAGE THRESHOLD (V) ON HIGH-VOLTAGE THRESHOLD vs. TEMPERATURE toc V CC (V).83 ON LOW-VOLTAGE THRESHOLD (V) ON LOW-VOLTAGE THRESHOLD vs. TEMPERATURE toc ON HYSTERESIS (V) ON HYSTERESIS vs. TEMPERATURE toc VOUT LOW (V) V OUT LOW vs. I LOAD T A = +85 C T A = +5 C T A = -0 C toc SENSE REGULATION VOLTAGE (mv) SENSE REGULATION VOLTAGE vs. V toc I LOAD (ma) V (V) 6

7 PIN NAME FUNCTION ON Pin Description On/Off Control Input. ON is used to implement the undervoltage lockout threshold and resets the part after a fault condition (see the Detailed Description section). Power-Good Comparator Input. Connect a resistive divider from output to to to monitor the output voltage (see the Power-Good Detection section). is also used as a feedback for the current-limit foldback function. 3 Open-Drain Power-Good Output. is high when V is higher than V H. is low when V is lower than V L. Ground 5 Timing Input. Connect a capacitor from to to program the maximum time the part is allowed to remain in current limit (see the section). 6 Gate-Drive Output. The high-side gate drive for the external n-channel MOSFET (see the section). 7 SENSE Current-Sense Input. Connect a sense resistor from V CC to SENSE and the drain of the external n-channel MOSFET. 8 V CC Power-Supply Input. Bypass V CC to with a 0.µF capacitor. Input voltage range is from +9V to +80V. 7

8 V CC SENSE Functional Diagram V P GEN REF GEN 0.5V CHARGE PUMP AND DRIVER OPEN DRAIN.33V ON V CC UNDERVOLTAGE LOCKOUT 8.3V LOGIC V P 0.5V 80µA.33V 3µA 8

9 Detailed Description The is a fully integrated hot-swap controller for positive supply rails. The device allows for the safe insertion and removal of circuit cards into live backplanes without causing glitches on the backplane power-supply rail. During startup the acts as a current regulator using an external sense resistor and MOSFET to limit the amount of current drawn by the load. The features latched-off fault management. When an overcurrent or an overtemperature fault occurs, the turns the external MOSFET off and keeps it off. After the fault condition goes away, cycle the power supply or toggle ON low and high again to unlatch the device. The operates from +9V to +80V supply voltage range and has a default undervoltage lockout (UVLO) set to +8.3V. The UVLO threshold is adjustable using a resistive divider connected from V CC to ON to (see R and R in Figure 5). The monitors the input voltage, the output voltage, the output current, and the die temperature. This device features a power-good output () to indicate the status of the output voltage by monitoring the voltage at (see the Power-Good Detection section). As shown in Figure 5, a sense resistor is connected between V CC and SENSE to sense the load current. The device regulates the voltage across the sense resistor (V IN - V SENSE ) to 7mV when the voltage at 0.5V. The current-limit threshold (V SENSETRIP ) decreases linearly from 7mV to mv as decreases from 0.5V to 0V. An undervoltage fault is detected when ON goes below the threshold, V ONL =.33V, which causes the voltage at to go low, and results in turning off the MOSFET. To turn the MOSFET on again, ON must pass the V ONH =.33V threshold. V IN V R SENSE 0.05Ω Q IRF530 C L R 9.9kΩ 0.µF R5 0Ω V CC SENSE D CMPZ58B R6 kω C 0nF R3 59kΩ R7 kω ON R 3.kΩ R 3.57kΩ 5 3 C 0.68µF Figure 5. Application Circuit 9

10 Applications Information Hot-Circuit Insertion When circuit boards are inserted into a live backplane, the supply bypass capacitors on the boards draw high peak currents from the backplane power bus as they charge up. The transient currents can permanently damage the connector pins and glitch the system supply, causing other boards in the system to reset. Power-Up Sequence The power supply on a board is controlled by placing an external n-channel MOSFET (Q) in the power path (Figure 5). Resistor R SENSE provides current detection and capacitor C provides control of the slew rate. Resistor R6 provides current control-loop compensation while R5 prevents high-frequency oscillations in Q. Resistors R and R provide undervoltage sensing. After the power pins first make contact, transistor Q is turned off. When the voltage at ON exceeds the turn-on threshold voltage, the voltage on V CC exceeds the undervoltage lockout threshold, and the voltage on is less than.33v, transistor Q turns on (Figure 6). The voltage at rises with a slope equal to 0µA/C and the supply inrush current is set at: I INRUSH = C L x 0µA/C When the voltage across the current-sense resistor R SENSE reaches V SENSETRIP, then the inrush current is limited by the internal current-limit circuitry that adjusts the voltage on to maintain a constant voltage across the sense resistor. Once the voltage at the output has reached its final value, as sensed by resistors R3 and R, goes high. Short-Circuit Protection The features a programmable foldback current limit with an electronic circuit breaker that protects against short circuits or excessive supply currents. The current limit is set by placing a sense resistor between V CC (pin 8) and SENSE (pin 7). To prevent excessive power dissipation in the pass transistor and to prevent voltage spikes on the input supply during short-circuit conditions at the output, the current folds back as a function of the output voltage that is sensed at (Figure 7). When the voltage at is 0V, the current-limit circuit drives to force a constant mv drop across the sense resistor. As the output voltage at increases, the voltage across the sense resistor increases until reaches 0.5V, at the point that the voltage across the sense resistor is held constant at 7mV. The maximum current limit is calculated as: I LIMIT = 7mV/R SENSE For a 0.05Ω sense resistor, the current limit is set at.88a and folds back to 80mA when the output is shorted to ground. The also features a variable overcurrent response time. The time required to regulate Q s drain current depends on: Q s input capacitance. capacitor C and compensation resistor R6. The internal delay from SENSE to. Figure 8 shows the delay from a voltage step at SENSE until voltage starts falling, as a function of overdrive. POWER-UP WAVEFORMS V CC - V SENSE 7mV I SENSE A/div 0ms/div Figure 6. Power-Up Waveforms OUTPUT mv 0V 0.5V V Figure 7. Current-Limit Sense Voltage vs. Feedback Voltage 0

11 PROPAGATION DELAY (µs) RESPONSE TIME TO OVERCURRENT SHORT-CIRCUIT WAVEFORMS OUTPUT I SENSE A/div V CC - V SENSE (mv) 0ms/div V/div Figure 8. Response Time to Overcurrent provides a method for programming the maximum time the device is allowed to operate in current limit. When the current-limit circuitry is not active, is pulled to by a 3µA current source. After the current-limit circuit becomes active, an 80µA pullup current source is connected to and the voltage rises with a slope equal to 77µA/C as long as the current-limit circuit remains active. Once the desired maximum current-limit time is chosen, the capacitor value is calculated using the following equations: C(nF) = 65 x t(ms) or T LIMIT = (C /80µA) x.33v When the current-limit circuit turns off, is discharged to by the 3µA current source. Whenever reaches.33v, the internal fault latch is set. is immediately pulled to and is pulled back to by the 3µA current source. When falls below 0.5V, ON is pulsed low to reset the internal fault latch. The waveform in Figure 9 shows how the output latches off following a short circuit. The drop across the sense resistor is held at mv as the timer ramps up. Since the output did not rise, remains below 0.5V and the circuit latches off. For Figure 9, C T = 00nF. Undervoltage and Overvoltage Detection ON can be used to detect an undervoltage condition at the power-supply input. ON is internally connected to an analog comparator with 80mV of hysteresis. If ON falls below its threshold voltage (.33V), is pulled low and is held low until ON is high again. Figure 9. Short-Circuit Waveforms Figure 0 shows an overvoltage detection circuit. When the input voltage exceeds the Zener diode s breakdown voltage, D turns on and starts to pull high. After is pulled higher than.33v, the fault latch is set and is pulled to immediately, turning off transistor Q (see Figure ). Operation is restored either by interrupting power or by pulsing ON low. Power-Good Detection The includes a comparator for monitoring the output voltage. The noninverting input () is compared against an internal.33v precision reference and exhibits 80mV hysteresis. The comparator s output () is an open drain one capable of operating from a pullup as high as 80V. The can be used to directly enable/disable a power module with an active-high enable input. Figure shows how to use to control an active-low enable-input power module. Signal inversion is accomplished by transistor Q and R7 or use MAX5933. Supply Transient Protection The is 00% tested and guaranteed to be safe from damage with supply voltages up to 80V. However, spikes above 85V may damage the device. During a short-circuit condition, the large change in currents flowing through the power-supply traces can cause inductive voltage spikes that could exceed 85V. To minimize the spikes, the power-trace parasitic inductance should be minimized by using wider traces or heavier trace plating and a 0.µF bypass capacitor placed between V CC and. A transient voltage suppressor (TVS) at the input can also prevent damage from voltage surges.

12 V IN SHORT PIN R 9.9kΩ D 30V N556B 0.µF R SENSE 0.05Ω R5 0Ω Q IRF V CC SENSE D CMPZ58B R6 kω C 0nF R3 59kΩ R7 kω C L ON R 3.kΩ 5 3 R 3.57kΩ C 0.68µF Figure 0. Overvoltage Detection OVERVOLTAGE WAVEFORMS 0µs/div Figure. Overvoltage Waveforms IN I SENSE 5A/div 0V/div OUTPUT Voltage A curve of Gate Drive vs. V CC is shown in Figure 3. is clamped to a maximum voltage of 8V above the input voltage. At a minimum input-supply voltage of 9V, the minimum gate-drive voltage is.5v. When the inputsupply voltage is higher than 0V, the gate-drive voltage is at least 0V and a standard n-channel MOSFET can be used. In applications over a 9V to 0V range, a logic-level n-fet must be used with a proper protection Zener diode between its gate and source (as D shown in Figure 5). Thermal Shutdown If the die temperature reaches +50 C, an overtemperature fault is generated. As a result, goes low and turns the external MOSFET off. The die temperature must cool down below +30 C before the overtemperature fault condition is removed.

13 V IN SHORT PIN R 9kΩ 0.µF R SENSE 0.0Ω R5 0Ω Q IRF V CC SENSE D CMPZ58B R6 kω C 0nF R3 3kΩ R7 7kΩ C L 0µF V IN+ V OUT+ ON/OFF V IN- V OUT- V OUT ON R 0.kΩ 5 3 R.kΩ C 0.68µF Figure. Active-Low Enable Module DRIVE (V - VCC) (V) DRIVE vs. V CC Layout Considerations To achieve accurate current sensing, a Kelvin connection is recommended. The minimum trace width for oz copper foil is 0.0in per amplifier to make sure the trace stays at a reasonable temperature. Using 0.03in per amplifier or wider is recommended. Note that oz copper exhibits a sheet resistance of about 530µΩ/square. Small resistances add up quickly in high-current applications. To improve noise immunity, connect the resistor-divider to ON close to the device and keep traces to V CC and short. A 0.µF capacitor from ON to also helps reject induced noise. Figure shows a layout that addresses these issues V CC (V) External MOSFET must be thermally coupled to the to ensure proper thermal shutdown operation (see Figure ). Figure 3. Gate Drive vs. Supply Voltage 3

14 Chip Information TRANSISTOR COUNT: 573 PROCESS: BiCMOS IRF530 Figure. Recommended Layout for R, R, and R SENSE Typical Application Circuit V IN R SENSE 0.0Ω Q IRF530 C L *SMBJ5A R 9.9kΩ 0.µF R5 0Ω V CC SENSE D CMPZ58B R6 kω C 0nF R3 59kΩ R7 kω ON R 3.kΩ R 3.57kΩ 5 3 C 0.68µF *DIODES, INC.

15 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to N E H INCHES MILLIMETERS DIM MIN MAX MIN MAX A A B C e BSC.7 BSC E H L SOICN.EPS TOP VIEW VARIATIONS: DIM D D D INCHES MILLIMETERS MIN MAX MIN MAX N MS AA AB AC D A C e B A FRONT VIEW L SIDE VIEW 0-8 PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE,.50" SOIC APPROVAL DOCUMENT CONTROL NO. REV. -00 B Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 0 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.