Positive High-Voltage, Hot-Swap Controllers

Transcription

1 9-363; Rev ; 7/0 Positive High-Voltage, Hot-Swap Controllers General Description The fully integrated hot-swap controllers for +9V to +80V positive supply rails (MAX597A/B/C), allow for the safe insertion and removal of circuit cards into live backplanes without causing glitches on the backplane power-supply rail. The MAX597B is pin- and function-compatible with the LT6-. The other devices offer added features such as a choice of active-high or active-low power-good outputs (/), latched/autoretry fault management, and autoretry duty-cycle options of 3.7 or 0.9% (see the Selector Guide). The MAX5933A MAX5933F are available with a default undervoltage lockout threshold of +3V and operate over a supply voltage range of +33V to +80V. The MAX597A/B/C are available with a default undervoltage of +8.3V. All devices feature a programmable analog foldback current limit. If the device remains in current limit for more than a programmable time, the external n-channel MOSFET is either latched off (MAX5933A/ MAX5933C/MAX597A) or is set to automatically restart after a timeout delay (MAX5933B/MAX5933D/MAX5933E/ MAX5933F/MAX597B/MAX597C). The MAX5933_ and MAX597_ operate in the extended temperature range of -0 C to +85 C. These devices are available in an 8-pin SO package. Hot Board Insertion Electronic Circuit Breakers Industrial High-Side Switch/Circuit Breakers Network Routers and Switches V/8V Industrial/Alarm Systems Applications Features Pin- and Function-Compatible with the LT6- (MAX597B) Provides Safe Hot Swap for +9V to +80V Power- Supply Range (MAX597A/B/C) Safe Board Insertion and Removal from Live Backplanes Latched/Autoretry Management Active-Low or Active-High Power-Good Output Programmable Foldback Current Limiting High-Side Drive for an External N-Channel MOSFET Built-In Thermal Shutdown Undervoltage Lockout (UVLO) Overvoltage Protection User-Programmable Supply Voltage Power-Up Rate Ordering Information PART TEMP RANGE PIN-PACKAGE MAX5933_ESA* -0 C to +85 C 8 SO MAX597_ESA* -0 C to +85 C 8 SO *Insert the desired suffix from the Selector Guide into the blank to complete the part number. Typical Application Circuit and Pin Configuration appear at end of data sheet. Selector Guide PART LATCHED FAULT PROTECTION AUTORETRY FAULT PROTECTION OUTPUT LOGIC DUTY CYCLE (%) DEFAULT UVLO (V) SUPPLY VOLTAGE RANGE (V) MAX5933A Yes High 3 33 to 80 MAX5933B Yes High to 80 MAX5933C Yes Low 3 33 to 80 MAX5933D Yes Low to 80 MAX5933E Yes High to 80 MAX5933F Yes Low to 80 MAX597A Yes Low to 80 MAX597B Yes High to 80 MAX597C Yes Low to 80 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 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 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 Lead Temperature (soldering, 0s) C ESD Rating (Human Body Model)...000V (V CC = +V (MAX597A/B/C), V CC = +8V (MAX5933A MAX5933F), = 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 MAX597A/B/C 9 80 MAX5933A MAX5933F Supply Current I CC V ON = 3V, V CC = 80V. 3.5 ma V CC low-to-high MAX597A/B/C V CC Undervoltage Lockout V LKO transition MAX5933A MAX5933F V CC Undervoltage Lockout Hysteresis MAX597A/B/C 0. V LKOHYST MAX5933A MAX5933F 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 V CC(MIN) 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 V V V 0.05 mv/v Pullup Current I UP Charge pump on, V = 7V µa Pulldown Current I DN Any fault condition, V = V ma MAX5933A MAX5933F V CC = 0.8V to 0V, MAX597A/B/C External N-Channel Gate Drive V V - V CC V CC = 0V to 80V, MAX597A/B/C Pullup Current I UP V = 0V µa Pulldown Current I ON V = V MAX5933A MAX5933D, MAX597A/B/C MAX5933E/MAX5933F ON Logic-High Threshold V ONH ON low-to-high transition V ON Logic-Low Threshold V ONL ON high-to-low transition V mv V µa

3 ELECTRICAL CHARACTERISTICS (continued) (V CC = +V (MAX597A/B/C), V CC = +8V (MAX5933A MAX5933F), = 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 Hysteresis V ONHYST 80 mv ON Input Bias Current I INON V ON = 0V - + µa Leakage Current I OH V = 80V 0 µa Leakage Current I OL V = 80V 0 µa / Output Low I O = ma 0. Voltage 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 ON Low-to- Low Propagation Delay ON High-to- High Propagation Delay Low-to- Low Propagation Delay High-to- High Propagation Delay (V CC - V SENSE ) High-to- Low Propagation Delay t PHLON C = 0, Figures, 6 µs t PLHON C = 0, Figures,.7 µs t PHL Figures, 3 3. µs 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 otherwise noted. V 3

4 V+ = 5V 5kΩ Figure. Test Circuit ON ON V CC V MAX5933_ MAX597_ SENSE 0nF.33V.33V 5V t PLHON t PHLON V Test Circuit and Timing Diagrams.33V.33V t PLH t PHL V V Figure 3. to Timing V CC - SENSE 7mV t PHLSENSE V CC Figure. ON to Timing Figure. SENSE to Timing

5 (V CC = +8V, T A = +5 C, unless otherwise noted.) ICC (ma) HIGH-VOLTAGE THRESHOLD (V) T A = -0 C I CC vs. V CC T A = +5 C V CC (V) T A = +85 C HIGH-VOLTAGE THRESHOLD vs. TEMPERATURE MAX5933 toc0 MAX5933 toc0 ICC (ma) HYSTERESIS (V) I CC vs. TEMPERATURE V CC = 8V (MAX5933_/MAX597_) V CC = V (MAX597_) 0 HYSTERESIS vs. TEMPERATURE 0.0 Typical Operating Characteristics MAX5933 toc0 MAX5933 toc05 LOW-VOLTAGE THRESHOLD (V) I PULLUP CURRENT (µa) LOW-VOLTAGE THRESHOLD vs. TEMPERATURE I PULLUP CURRENT vs. TEMPERATURE -3 MAX5933 toc03 MAX5933 toc06 DRIVE (V - VCC) (V) DRIVE vs. TEMPERATURE V CC = 8V (MAX5933_/MAX597_) V CC = 0.8V (MAX597_) MAX5933 toc07 DRIVE (V - VCC) (V) MAX597_ DRIVE vs. V CC MAX5933 toc V CC (V) 5

6 Typical Operating Characteristics (continued) (V CC = +8V, T A = +5 C, unless otherwise noted.) PULLUP CURRENT (µa) ON HIGH-VOLTAGE THRESHOLD (V) PULLUP CURRENT vs. TEMPERATURE ON HIGH-VOLTAGE THRESHOLD vs. TEMPERATURE.83 MAX5933 toc09 MAX5933 toc PULLUP CURRENT (µa) ON LOW-VOLTAGE THRESHOLD (V) MAX5933_ PULLUP CURRENT vs. V CC T A = +5 C T A = 0 C T A = +85 C T A = -0 C V CC (V) ON LOW-VOLTAGE THRESHOLD vs. TEMPERATURE.05 MAX5933 toc0 MAX5933 toc3 PULLUP CURRENT (µa) ON HYSTERESIS (V) MAX597_ PULLUP CURRENT vs. V CC T A = +5 C T A = 0 C T A = +85 C T A = -0 C V CC (V) ON HYSTERESIS vs. TEMPERATURE MAX5933 toc MAX5933 toc VOUT LOW (V) V OUT LOW vs. I LOAD T A = +85 C T A = +5 C T A = -0 C MAX5933 toc5 SENSE REGULATION VOLTAGE (mv) SENSE REGULATION VOLTAGE vs. V MAX5933 toc I LOAD (ma) V (V) 6

7 PIN NAME FUNCTION ON 3 / Ground 5 Pin Description ON/OFF Control Input. ON is used to implement the undervoltage lockout threshold and resets the part after a fault condition for the latched-off version (MAX5933A/MAX5933C/MAX597A, 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. Open-Drain Power-Good Output. is high ( is low) when V is higher than V H. is low ( is high) when V is lower than V L. 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- D r i ve O utp ut. The hi g h- si d e g ate d r i ve for the exter nal N - channel M OS FE T ( see the G ATE V ol tag e secti on). 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 for the MAX597A/B/C. Input voltage range is from +33V to +80V for the MAX5933A MAX5933F. 7

8 () ON OPEN DRAIN MAX5933_ MAX597_ REF GEN.33V 0.5V V CC V P GEN V UVLO 0.5V mv TO 7mV UNDERVOLTAGE LOCKOUT V CC SENSE LOGIC CHARGE PUMP AND DRIVER V P 80µA Functional Diagram.33V 3µA *0.75µA ( ) FOR THE MAX5933C/D/F AND THE MAX597A/C. *FOR THE MAX5933E/MAX5933F. 8

9 Detailed Description The MAX5933_ and MAX597_ are fully integrated hotswap controllers for positive supply rails. The devices allow for the safe insertion and removal of circuit cards into live backplanes without causing glitches on the backplane power-supply rail. During startup, the MAX5933_ and MAX597_ act as current regulators using an external sense resistor and a MOSFET to limit the amount of current drawn by the load. The MAX5933_ operate from a +33V to +80V supply voltage range and have a default undervoltage lockout (UVLO) set to +3V. The MAX597_ operate from a +9V to +80V supply voltage range and have a default UVLO set to +8.3V. The UVLO threshold is adjustable using a resistive divider connected from V CC to ON to (see Figure 5). V IN V R 9.9kΩ 0.µF ON R SENSE 0.05Ω R5 0Ω Q IRF V CC SENSE The MAX5933_ and MAX597_ monitor the input voltage, the output voltage, the output current, and the die temperature. These devices feature power-good outputs (/) 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 regulate 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) and the voltage at goes low as a result to turn off the MOSFET. ON must pass the V ONH =.33V threshold to turn on the MOSFET again. D CMPZ58B R6 kω C 0nF R3 59kΩ R7 kω C L R 3.kΩ MAX5933A 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 when 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, 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 or goes low. Short-Circuit Protection The MAX5933_/MAX597_ feature 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 this point, 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 MAX5933_/MAX597_ also feature 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 3) 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 V CC - V SENSE (mv) 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: 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. SHORT-CIRCUIT WAVEFORMS 0ms/div Figure 9. Short-Circuit Waveforms OUTPUT I SENSE A/div V/div 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 MAX5933_/MAX597_ include 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 open drain and capable of operating from a pullup as high as 80V. The is similar to with an opposite polarity (active low) output. 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. Supply Transient Protection The MAX5933_/MAX597_ are 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 which 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 R 3.kΩ D 30V N556B Figure 0. Overvoltage Detection C 0.68µF OVERVOLTAGE WAVEFORMS 0µs/div Figure. Overvoltage Waveforms 0.µF 5 ON IN I SENSE 5A/div 0V/div OUTPUT R SENSE 0.05Ω MAX5933B MAX597B R5 0Ω Q IRF V CC SENSE 3 D CMPZ58B R6 kω C 0nF R3 59kΩ R 3.57kΩ R7 kω 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 33V, the minimum gate drive voltage is 0V. When the input supply voltage is higher than 0V, the gate-drive voltage is at least 0V and a standard n-channel MOSFET can be used. Using the MAX597 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 (see D in Figure 5). Thermal Shutdown If the MAX5933_/MAX597_ die temperature reaches +50 C, an overtemperature fault is generated. As a result, goes low and turns the external MOSFET off. The MAX5933_/MAX597_ die temperature must cool down below +30 C before the overtemperature fault condition is removed. C L

13 V IN SHORT PIN R 9kΩ R 0.kΩ C 0.68µF 0.µF ON Figure. Active-Low Enable Module DRIVE (V - VCC) (V) DRIVE vs. V CC R SENSE 0.0Ω MAX5933A R5 0Ω Q IRF V CC SENSE V CC (V) Figure 3. Gate Drive vs. Supply Voltage 3 D CMPZ58B R6 kω C 0nF R3 3kΩ R.kΩ R7 7kΩ C L 0µF 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 ensure the trace stays at a reasonable temperature. However, 0.03in. per amplifier or wider is recommended. Note that oz copper exhibits a sheet resistance of approximately 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. It is recommended that oz copper is used, particularly as the external MOSFET must be thermally coupled to the MAX5933_/MAX597_ to ensure proper thermal-shutdown operation. V IN+ V OUT+ ON/OFF V IN- V OUT- V OUT 3

14 V IN MAX5933_ MAX597_ IRF530 Figure. Recommended Layout for R, R, and RSENSE *SMBJ5A R 9.9kΩ 0.µF R SENSE 0.0Ω R5 0Ω Q IRF V CC SENSE Chip Information TRANSISTOR COUNT: 573 PROCESS: BiCMOS TOP VIEW ON () Typical Application Circuit D CMPZ58B R6 kω C 0nF 3 MAX5933_ MAX597_ SO ( ) ONLY FOR THE MAX5933C/D/F/MAX597A/MAX597C. Pin Configuration R3 59kΩ R7 kω V CC SENSE C L ON R 3.kΩ MAX5933A 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 TOP VIEW D e B A FRONT VIEW E A H C L SIDE VIEW 0-8 INCHES MILLIMETERS DIM MIN MAX MIN MAX A A B C e BSC.7 BSC E H L VARIATIONS: DIM D D D INCHES MIN MAX MIN MAX N MS AA AB AC PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE,.50" SOIC APPROVAL MILLIMETERS DOCUMENT CONTROL NO. REV. -00 B SOICN.EPS 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.