LM5060MMX

LM5060 High-Side Protection Controller with Low Quiescent Current September 22, 2010 LM5060 High-Side Protection Controller with Low Quiescent Current General Description The LM5060 high-side protection controller provides intelligent control of a high-side N-Channel MOSFET during normal on/off transitions and fault conditions. In-rush current is controlled by the nearly constant rise time of the output voltage. A power good output indicates when the output voltage reaches the input voltage and the MOSFET is fully on. Input UnderVoltage Lock-Out, with hysteresis, is provided as well as programmable input Over-Voltage Protection. An enable input provides remote On / Off control. The programmable Under-Voltage Lock-Out input can be used as second enable input for safety redundancy. A single capacitor programs the initial start-up VGS fault detection delay time, the transition VDS fault detection delay time, and the continuous Over-Current VDS fault detection delay time. When a detected fault condition persists longer than the allowed fault delay time, the MOSFET is latched off until either the Enable input or the Under-Voltage Lock-Out input is toggled low and then high. Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Available in Automotive grade / AEC Q-100 Wide operating input voltage range: +5.5V to +65V Less than 15 µA quiescent current in disabled mode Controlled output rise time for safe connection of capacitive loads Charge pump gate driver for external N-Channel MOSFET Adjustable Under-Voltage Lock-Out (UVLO) with hysteresis UVLO serves as second enable input for systems requiring safety redundancy Programmable fault detection delay time MOSFET latched off after load fault is detected Active low open drain POWER GOOD (nPGD) output Adjustable input Over-Voltage Protection (OVP) Immediate restart after Over-Voltage shutdown Applications ■ Automotive Body Electronics ■ Industrial Power Distribution and Control Package ■ 10-Lead MINI-SOIC Typical Application 30104201 © 2010 National Semiconductor Corporation 301042 www.national.com LM5060 Connection Diagram 30104202 10-Lead MINI-SOIC Package (MSOP) NS Package Number MUB10A Ordering Information Order Number LM5060MM LM5060MMX LM5060Q1MM LM5060Q1MMX Grade Standard Standard Automotive Automotive Package Type 10 Lead MSOP 10 Lead MSOP 10 Lead MSOP 10 Lead MSOP NSC Package Drawing MUB10A MUB10A MUB10A MUB10A Supplied As 1000 Units on Tape and Reel 3500 Units on Tape and Reel 1000 Units on Tape and Reel 3500 Units on Tape and Reel Automotive Grade (Q) product incorporates enhanced manufacturing and support processes for the automotive market, including defect detection methodologies. Reliability qualification is compliant with the requirements and temperature grades defined in the AEC Q100 standard. Automotive Grade products are identified with the letter Q. For more information go to http://www.national.com/automotive. Pin Descriptions Pin No. 1 Name SENSE Description Input Voltage Sense Applications Information A constant current sink (16 μA typical) at the SENSE pin flows through an external resistor to set the threshold for fault detection. 2 VIN The operating voltage range is 5.5V to 65V. The internal power-on-reset (POR) circuit typically Supply Voltage Input switches to the active state when the VIN pin is greater than 5.1V. A small ceramic bypass capacitor close to this pin is recommended to suppress noise. An external resistor divider from the system input voltage sets the Over-Voltage turn-off Over-Voltage threshold. The GATE pin is pulled low when OVP exceeds the typical 2.0V threshold, but the Protection Comparator controller is not latched off. Normal operation resumes when the OVP pin falls below typically Input 1.76V. The UVLO pin is used as an input Under-Voltage Lock-Out by connecting this pin to a resistor divider between input supply voltage and ground. The UVLO comparator is activated when EN Under-Voltage Lockis high. A voltage greater than typically 1.6V at the UVLO pin will release the pull down devices Out Comparator Input on the GATE pin and allow the output to gradually rise. A constant current sink (5.5 µA typical) is provided to guarantee the UVLO pin is low in an open circuit condition. A voltage less than 0.8V on the EN pin switches the LM5060 to a low current shutdown state. A voltage greater than 2.0V on the EN pin enables the internal bias circuitry and the UVLO comparator. The GATE pin pull-up bias is enabled when both EN and UVLO are in the high state. A constant current sink (6 µA typical) is provided to guarantee the EN pin is low in an open circuit condition. An external capacitor connected to this pin sets the VDS fault detection delay time. If the TIMER pin exceeds the 2.0V threshold condition, the LM5060 will latch off the MOSFET and remain off until either the EN, UVLO or VIN (POR) input is toggled low and then high. 3 OVP 4 UVLO 5 EN Enable Input 6 7 GND TIMER Circuit ground Timing capacitor www.national.com 2 LM5060 Pin No. 8 9 Name nPGD OUT Description Fault Status Output VoltageSense Applications Information An open drain output. When the external MOSFET VDS decreases such that the OUT pin voltage exceeds the SENSE pin voltage, the nPGD indicator is active (low = no fault). Connect to the output rail (external MOSFET source). Internally used to detect VDS and VGSconditions. Connect to the external MOSFET’s gate. A charge-pump driven constant current source (24 µA typical) charges the GATE pin. An internal zener clamps the GATE pin at typically 16.8V above the OUT pin. The ΔV/Δt of the output voltage can be reduced by connecting a capacitor from the GATE pin to ground. 10 GATE Gate drive output 3 www.national.com LM5060 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN to GND (Note 4, Note 5) SENSE, OUT to GND (Note 6) GATE to GND (Note 4, Note 6) EN, UVLO to GND (Note 5) nPGD, OVP to GND TIMER to GND ESD Rating, HBM (Note 2) -0.3V to 75V -0.3V to 75V -0.3V to 75V -0.3V to 75V -0.3V to 75V -0.3V to 7V 2 kV Storage Temperature Peak Reflow Temperature(Note 3) Junction Temperature −65°C to + 150°C 260°C 150°C Operating Ratings VIN Supply Voltage EN Voltage UVLO Voltage nPGD Off Voltage nPGD Sink Current Junction Temperature Range (Note 1) 5.5V to 65V 0.0V to 65V 0.0V to 65V 0V to 65V 0mA to 5mA −40°C to + 125°C Electrical Characteristics Unless otherwise stated the following conditions apply: VIN = 14V, EN =2.00V, UVLO =2.00V, OVP = 1.50V, and TJ = 25°C. Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the operating junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Symbol VIN Pin IIN-EN IIN-DIS IIN-STB POREN POREN-HYS OUT Pin IOUT-EN IOUT-DIS SENSE Pin ISENSE VOFFSET IRATIO OVP Input OVPTH OVPHYS OVPDEL OVPBIAS UVLO Input UVLOTH UVLOHYS UVLOBIAS EN Input ENTHH ENTHL ENHYS ENBIAS High-level input voltage Low-level input voltage EN Threshold Hysteresis EN Pin Pull-down current Gate Charge (Sourcing) Current On-state Gate Discharge (Sinking) Current Off state Gate Discharge (Sinking) Current Fault state 2.00 200 6 0.80 8.0 V V mV µA UVLO Threshold UVLO Hysteresis UVLO Pin Pull-Down Current UVLO Pin Threshold Voltage Rising 1.45 120 3.8 1.6 180 5.5 1.75 230 7.2 V mV µA OVP Threshold OVP Hysteresis OVP Delay Time OVP Pin Bias Current Delay from OVP Pin > OVPTH to GATE low OVP = 1.9V OVP Pin Threshold Voltage Rising 1.88 2.0 240 9.6 0 2.12 0.50 V mV µs µA Threshold Programming Current VDS Comparator Offset Voltage ISENSE and IOUT-EN Current Ratio SENSE Pin Bias Current SENSE - OUT Voltage for Fault Detection ISENSE / IOUT-EN 13.6 -7.0 1.70 16 0 2.0 18.0 7.0 2.30 µA mV OUT Pin Bias Current, Enabled OUT Pin Leakage Current, Disabled (Note 4) OUT = VIN, Normal Operation Disabled, OUT = 0V, SENSE = VIN 5.0 8 0 11.0 µA μA Input Current, Enabled Mode Input Current, Disabled Mode Input Current, Standby Mode Power On Reset Threshold at VIN POREN Hysteresis EN = 0.50V UVLO = 0.00V VIN Rising VIN Falling 1.4 9 0.56 5.1 500 1.7 15 0.80 5.46 mA µA mA V mV Parameter Conditions Min Typ Max Units Gate Control (GATE Pin) IGATE IGATE-OFF IGATE-FLT On-state UVLO = 0.00V OUT < SENSE 17 24 2.2 80 31 µA mA mA www.national.com 4 LM5060 Symbol VGATE VGATE-TH VGATE-CLAMP Timer (TIMER Pin) VTMRH VTMRL ITIMERH ITIMERL ITIMERR tFAULT Parameter Gate output voltage in normal operation VGS Status Comparator Threshold voltage Conditions GATE - VIN Voltage GATE Pin Open GATE - OUT threshold voltage for TIMER voltage reset and TIMER current change Min 10 3.50 - Typ 12 5 16.8 Max 14 6.50 - Units V V V Zener Clamp between GATE Pin and IGATE-CLAMP = 0.1mA OUT Pin Timer Fault Threshold Timer Re-enable Threshold Timer Charge Current for VDS Fault Timer Start-Up Charge Current Timer Reset Discharge Current Fault to GATE Low delay TIMER Pin Voltage Rising TIMER pin Voltage Falling TIMER Charge current after Start-Up. VGS = 6.5V TIMER Charge current during Start-Up. VGS = 3.5V TIMER Pin = 1.5V TIMER Pin > 2.0V No load on GATE pin ISINK = 2 mA VnPGD = 10V 8.5 4.0 4.4 - 2.0 0.30 11 6 6 5 13.0 7.0 8.2 - V V µA µA mA µs Power Good (nPGD Pin) PGDVOL PGDIOH Output low voltage Off leakage current 80 0.02 205 1.00 mV µA Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur, including in-operability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. Operating Range conditions indicate the conditions at which the device is functional and the device should not be operated beyond such conditions. For guaranteed specifications and conditions, see the Electrical Characteristics table. Note 2: The Human Body Model (HBM) is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. Applicable standard is JESD-22–A114–C. Note 3: Soldering process must comply with National Semiconductor's Reflow Temperature Profile specifications. Reflow temperature profiles are different for lead-free and non-lead-free packages. Refer to the Packaging Data Book available from National Semiconductor, or : www.national.com/analog/packaging Note 4: The GATE pin voltage is typically 12V above the VIN pin when the LM5060 is enabled. Therefore, the Absolute Maximum Rating for VIN (75V) applies only when the LM5060 is disabled, or for a momentary surge to that voltage since the Absolute Maximum Rating for the GATE pin is also 75V. Note 5: The minimum voltage of -1V is allowed if the current is limited to below -25 mA. Also it is assumed that the negative voltage on the pins only occur during reverse battery condition when a positive supply voltage (Vin) is not applied. Note 6: The minimum voltage of -25V is allowed if the current is limited to below -25 mA. Also it is assumed that the negative voltage on the pins only occur during reverse battery condition when a positive supply voltage (VIN) is not applied. 5 www.national.com LM5060 Typical Performance Characteristics VIN Pin Current vs. VIN Pin Voltage VGATE, VIN Voltage vs. Input Voltage 30104203 30104204 OUT Pin Current (IOUT-EN) vs. VIN Voltage GATE Current (IGATE) vs VIN Voltage 30104205 30104206 SENSE Current (ISENSE) vs VIN Voltage nPGD Low Voltage (PGDVOL vs Sink Current 30104207 30104208 www.national.com 6 LM5060 GATE Pull-Down Current Off (IGATE-OFF) vs. GATE Voltage EN Threshold Voltage (ENTH) vs. Temperature 30104209 30104210 UVLO Threshold Voltage (UVLOTH) vs. Temperature GATE Pull-Down Current Fault (IGATE-FLT) vs. GATE Voltage 30104259 30104211 UVLO, EN Current vs. Temperature OVP Threshold (OVPTH), Hysteresis (OVPHYS) vs. Temperature 30104212 30104213 7 www.national.com LM5060 VGS Comparator Threshold Voltage (VGATE-TH) vs. Temperature VDS Comparator Offset Voltage (VOFFSET) vs. Temperature 30104214 30104215 GATE Current (IGATE) vs. Temperature GATE Output Voltage (VGATE) vs. Temperature 30104216 30104217 Gate Pull-Down Current - Fault (IGATE-FLT) vs. Temperature VIN Pin Current (IEN) vs EN Voltage 30104218 30104219 www.national.com 8 LM5060 nPGD Low Voltage (PGDVOL) vs. Temperature 30104220 9 www.national.com LM5060 Block Diagram 30104221 www.national.com 10 LM5060 30104222 FIGURE 1. Basic Application Circuit Functional Description The LM5060 is designed to drive an external high-side Nchannel MOSFET. Over-Current protection is implemented by sensing the voltage drop across the MOSFET. When an adjustable voltage drop threshold is exceeded, and an adjustable time period has elapsed, the MOSFET is disabled. Over-Voltage Protection (OVP) and Under-Voltage Lock-Out (UVLO) monitoring of the input line is also provided. A low state on the enable pin will turn off the N-channel MOSFET and switch the LM5060 into a very low quiescent current off state. An active low power good output pin is provided to report the status of the N-channel MOSFET. The waiting time before the MOSFET is turned off after a fault condition is detected can be adjusted with an external timer capacitor. Since the LM5060 uses a constant current source to charge the gate of the external N-channel MOSFET, the output voltage rise time can be adjusted by adding external gate capacitance. This is useful when starting up into large capacitive loads. POWER-UP SEQUENCE The basic application circuit is shown in Figure 1 and a normal start-up sequence is shown in Figure 2. Start-up of the LM5060 is initiated when the EN pin is above the (ENTHH) threshold (2.0V). At start-up, the timer capacitor is charged with a 6 µA (typical) current source while the gate of the external N-channel MOSFET is charged through the GATE pin by a 24 µA (typical) current source. When the gate-to-source voltage (VGS) reaches the VGATETH threshold (typically 5V) the VGS sequence ends, the timer capacitor is quickly discharged to 0.3V, and begins charging the timer capacitor with a11 µA current source. The timer capacitor will charge until either the VDS Comparator indicates that the drain-to-source voltage (VDS) has been reduced to a nominal value (i.e. no fault) or the voltage on the timer capacitor has reached the VTMRH threshold (i.e. fault). The VDS Comparator monitors the voltage difference between the SENSE pin and the OUT pin. The SENSE pin voltage is user programmed to be lower than the input supply voltage by selecting a suitable sense resistor value. When the OUT pin voltage exceeds the voltage at the SENSE pin, the nPGD pin is asserted low (i.e. no fault) and the timer capacitor is discharged. STATUS CONDITIONS Output responses of the LM5060 to various input conditions is shown in Table 1. The input parameters include Enable (EN), Under-Voltage Lock-Out (UVLO), Over-Voltage Protection (OVP), input voltage (VIN), Start-Up Fault (VGS) and Run Fault (VDS) conditions. The output responses are the VIN pin current consumption, the GATE charge current, the TIMER capacitor charge (or discharge) current, the GATE discharge current if the timer capacitor voltage has reached the VTMRH threshold (typically 2V), as well as the status of nPGD. 11 www.national.com LM5060 30104223 FIGURE 2. Voltages During Normal Start Up Sequence TABLE 1. Overview of Operating Conditions Input Conditions EN UVLO L L H H H L H L L H OVP (typ) 2V 5.10V >5.10V >5.10V >5.10V >5.10V SENSE-OUT NA NA SENSE>OUT SENSEOUT SENSEOUT SENSEOUT SENSE2V 5.10V OUT SENSE5V 1.4 mA 24 µA source Enabled Note †: The 2.2 mA sink current is valid for with the VIN pin ≥ 5.1V. When the VIN pin < 5.1V the sink current is lower. See ‘GATE Pin Off Current vs. VIN’ plot in Typical Performance Characteristics. GATE CONTROL A charge pump provides bias voltage above the input and output voltage to enhance the N-Channel MOSFET’s gate. When the system voltage is initially applied and both EN and UVLO are above their respective thresholds, the GATE pin is charged by the 24 µA (typical) current source. During normal operating conditions, the GATE pin voltage is clamped to approximately 16.8V above the OUT pin (i.e. VGS) by an internal zener. When either the UVLO input or the EN input is low, or when VIN is below the Power-On Reset voltage of 5.10V (typical), the GATE pin is discharged with a 2.2 mA (typical) current sink. When the timer capacitor is charged up to the VTMRH threshold (typically 2V) a fault condition is indicated and the gate of the external N-Channel MOSFET is discharged at a 80 mA (typical) rate . Additionally, when the OVP pin voltage is higher than the OVPTH threshold (typically 2V) a fault is indicated and the gate of the external N-Channel MOSFET is discharged at the same 80 mA (typical) rate. FAULT TIMER An external capacitor connected from the TIMER pin to the GND pin sets the fault detection delay time. If the voltage on the TIMER capacitor reaches the VTMRH threshold (2V typical) a fault condition is indicated. The LM5060 will latch off the MOSFET by discharging the GATE pin at a 80mA (typical) www.national.com 12 LM5060 rate, and will remain latched off until either the EN pin, the UVLO pin, or the VIN pin is toggled low and then high. The block diagram of the LM5060 shows the details of the TIMER pin. There are three relevant components to the TIMER pin’s function: 1. A constant 6 µA (typical) current source driving the TIMER pin. This current source is active when EN, UVLO, and VIN are all high. 2. A second current source (5 µA typical) is activated, for a total charge current of 11 µA (typical), only when the VGS sequence has completed successfully. 3. A pull-down current sink for the TIMER pin which resets the timer by discharging the timer capacitor. If EN, UVLO or VIN is low, or when OVP is high, the timer capacitor is discharged. When the VDS Fault Comparator detects a fault, (SENSE pin voltage higher than OUT pin voltage) the timer capacitor pull down is disabled and the timer capacitor is allowed to charge at the 11 µA (typical) rate. During Start-Up, the timer behaves as follows: After applying sufficient system voltage and enabling the LM5060 by pulling the EN and UVLO pins high, the timer capacitor will be charged with a 6 µA (typical) current source. The timer capacitor is discharged when the voltage difference between the GATE pin and the OUT pin (i.e. VGS of the external N-Channel MOSFET) reaches the VGATE-TH threshold (typically 5V). After discharging, the timer capacitor is charged with 11 µA until either the VTMRH threshold (typically 2V) is reached, or the sensed VDS voltage falls below the threshold of the VDS Fault Comparator, indicating the output voltage has reached the desired steady state level. The timer capacitor voltage waveforms are illustrated in Figure 2, Figure 3 and Figure 4. A timer capacitor is always necessary to allow some finite amount of time for the gate to charge and the output voltage to rise during startup. If an adequate timer capacitor value is not used, then the 6 µA of charge current would cause the TIMER pin voltage to reach the VTMRH fault threshold (typically 2V) prematurely and the LM5060 will latch off since a fault condition would have been indicated. Although not recommended, the timer function can be disabled by connecting the TIMER pin directly to GND. With this condition the TIMER pin voltage will never reach the VTMRH fault threshold (2V typical). The end result is that the fault latch-off protection is completely disabled, while the nPGD pin will continue to reflect the VDS Fault Comparator output. VGS CONSIDERATIONS The VGS Status Comparator shown in the LM5060 block diagram accomplishes two purposes: 1. As the gate of the external MOSFET is charged, the VGS voltage transitions from cut-off, through an active region, and into the ohmic region. The LM5060 provides two fault timer modes to monitor these transitions. The TIMER pin capacitor is initially charged with a constant 6 µA (typical) until either the MOSFET VGS reaches the VGATE–TH threshold (typically 5V) indicating that the MOSFET channel is at least somewhat enhanced, or the voltage on the TIMER pin reaches the VTMRH threshold (typically 2V) indicating a fault condition. If the MOSFET VGS reaches 5V threshold before the TIMER pin reaches the typical 2V timer fault threshold, the timer capacitor is then discharged to 300 mV, and then begins charging with 11 µA current source while the MOSFET transitions through the active region. The lower timer capacitor charge current during the initial start-up sequence allows more time before a fault is indicated. The turn-on time of the MOSFET will vary with input voltage, load capacitance, load resistance, as well as the MOSFET characteristics. 2. Figure 3 shows a start-up waveform with excessive gate leakage. The initial charge current on the timer capacitor is 6 µA (typical), while the simultaneous charge current to the gate is 24 µA (typical). Due to excessive gate leakage, the 24 µA is not able to charge the gate to the required typical 5V VGS threshold and the VDS Fault Comparator will indicate a fault when the timer capacitor is charged to the VTMRH fault threshold. When the timer capacitor voltage reaches theVTMRH fault threshold (typically 2V) the MOSFET gate is discharged at an 80 mA (typical) rate. 30104224 FIGURE 3. Voltages During Startup with VGS Gate Leakage Condition 13 www.national.com LM5060 VDS FAULT CONDITION The LM5060 includes a VDS Fault Comparator that senses the voltage difference between the SENSE pin and the OUT pin. If the voltage at the OUT pin falls lower than the voltage at the SENSE pin, the VDS Fault Comparator will trip and switch the nPGD pin to a high impedance state. It will also initiate charging of the capacitor on the TIMER pin with a 6 µA (typical) current source if VGS is less than than 5V, or a 11 µA (typical) current source if VGS is higher than 5V. If the voltage on the TIMER pin reaches the typical 2V fault threshold, the gate of the N-Channel MOSFET is pulled low with a 80 mA (typical) sink current. Figure 4 illustrates a VDS fault condition during start-up. The nPGD pin never switches low because the VDS fault comparator detects excessive VDS voltage throughout the entire sequence. OVER-CURRENT FAULT The VDS Fault Comparator can be used to implement an OverCurrent shutdown function. The VDS Fault Comparator monitors the voltage difference between the SENSE pin and the OUT pin. This is, essentially, the same voltage that is across the N-Channel MOSFET RDS(ON) less the threshold voltage that is set by the series resistor on the SENSE pin. The value of capacitor on the TIMER pin, the capacitor charge current (ITIMERH, 11 uA typical), along with the TIMER pin fault threshold (VTMRH) will determine the how long the N-Channel MOSFET will be allowed to conduct excessive current before the MOSFET is turned-off. When this delay time expires, the gate is discharged at a 80 mA rate. The LM5060 is intended for applications where precise current sensing is not required, but some level of fault protection is needed. Examples are applications where inductance or impedance in the power path limits the current rise in a short circuit condition. The Safe Operating Area (SOA) of the external N-Channel MOSFET should be carefully considered to ensure the peak drain-to-source current and the duration of the fault delay time is within the SOA rating of the MOSFET. Also note that the RDS(ON) variations of the external N-Channel MOSFET will affect the accuracy of the Over-Current detection. RESTART AFTER OVER-CURRENT FAULT EVENT When a VDS fault condition has occurred and the TIMER pin voltage has reached 2V, the LM5060 latches off the external MOSFET. In order to initiate a restart, either the EN pin, the VINpin, or the UVLO pin must be toggled low and then high. 30104225 FIGURE 4. Voltages During Startup with VDS Fault Condition ENABLE The LM5060 Enable pin (EN) allows for remote On/Off control. The Enable pin on/off thresholds are CMOS compatible. The external N-Channel MOSFET can be remotely switched Off by forcing the EN pin below the lower input threshold, ENTHL (800 mV). The external N-Channel MOSFET can be remotely switched On by forcing the EN pin above the upper input threshold, ENTHH (2.00V). Figure 5 shows the threshold levels of the Enable pin. When the EN pin is less than 0.5V (typical) the LM5060 enters a low current (disabled) state. The current consumption of the VIN pin in this condition is 9 µA (typical). 30104226 FIGURE 5. Enable Function Threshold Levels www.national.com 14 LM5060 UNDER-VOLTAGE LOCK-OUT (UVLO) The Under-Voltage Lock-Out function will turn off the external N-Channel MOSFET with a 2.2 mA (typical) current sink at the GATE pin. Figure 6 shows the threshold levels of the UVLO input. A resistor divider as shown in Figure 1 with R10 and R11 sets the voltage at which the UVLO function engages. The UVLO pin may also be used as a second enable pin for applications requiring a redundant, or secondary, shut-down control. Unlike the EN pin function, the UVLO function does not switch the LM5060 to the low current (disabled) state. If the Under-Voltage Lock-Out function is not needed, the UVLO pin should be connected to the VIN pin. The UVLO pin should not be left floating as the internal pull-down will keep the UVLO active. In addition to the programmable UVLO function, an internal Power-On-Reset (POR) monitors the voltage at the VIN pin and turns the MOSFET Off when VIN falls below typically 5.10V. OVPTH threshold (typically 2V). A resistor divider made up with R8 and R9, shown in Figure 1, sets the Over-Voltage Protection threshold. An internal 9.6 µs timer filters the output of the Over-Voltage Comparator to prevent noise from triggering an OVP event. An OVP event lasting longer than typically 9.6 µs will cause the GATE pin to be discharged with an 80 mA current sink and will cause the capacitor on the TIMER pin to be discharged. If the Over-Voltage Protection function is not needed, the OVP pin should be connected to GND. The OVP pin should not be left floating. RESTART AFTER OVP EVENT After the OVP function has been activated and the gate of the external N-Channel MOSFET has been pulled low, the OUT pin is likely to be low as well. However, an OVP condition will not cause the VDS Fault Comparator to latch off of the LM5060 because the capacitor on the TIMER pin is also discharged during an OVP event. After the OVP pin falls below the lower threshold (typically 1.76V), the LM5060 will re-start as described in the normal start-up sequence and shown in Figure 2. The EN, VIN, or UVLO pins do not need to be toggled low to high to re-enable the MOSFET after an OVP event. nPGD Pin The nPGD pin is an open drain connection that indicates when a VDS fault condition has occurred. If the SENSE pin voltage is higher than the OUT pin voltage the state of the nPGD pin will be high impedance. In the typical application, as shown in Figure 1, the voltage at the nPGD pin will be high during any VDS fault condition. The nPGD state is independent of the fault timer function. The resistance R4 should be selected large enough to safely limit the current into the nPGD pin. Limiting the nPGD low state current below 5 mA is recommended. 30104227 FIGURE 6. Under-Voltage Lock-Out Threshold Levels OVER-VOLTAGE PROTECTION (OVP) The Over-Voltage Protection function will turn off the external N-Channel MOSFET if the OVP pin voltage is higher than the 15 www.national.com LM5060 Application Information VDS FAULT DETECTION and SELECTING SENSE PIN RESISTOR RS The LM5060 monitors the VDS voltage of the external NChannel MOSFET. The drain to source voltage threshold (VDSTH), which is set with the resistor RS, is shown in Figure 7; VDSTH = (RS x ISENSE) - VOFFSET The MOSFET drain to source current threshold is: 30104230 FIGURE 8. Turn-On Time Extension where RDS(ON) is the resistive drop of the pass element Q1 in Figure 7, VOFFSET is the offset voltage of the VDS comparator and ISENSE (16 µA typical) is the threshold programming current. FAULT DETECTION DELAY TIME To allow the gate of the MOSFET adequate time to change, and to allow the MOSFET to conduct currents beyond the protection threshold for a brief period of time, a fault delay timer function is provided. This feature is important when drive loads which require a surge of current in excess of the normal ON current upon start up, or at any point in time, such as lamps and motors. A single low leakage capacitor (CTIMER) connected from the TIMER (pin 7), to ground sets the delay time interval for both the VGS status detection at start-up and for the subsequent VDS Over-Current fault detection. When the LM5060 is enabled under normal operating conditions the timer capacitor will begin charging at a 6 μA (typical) rate while simultaneously charging the gate of the external MOSFET at a 24 μA (typical) rate. The gate-to-source voltage (VGS) of the external MOSFET is expected to reach the 5V (typical) threshold before the timer capacitor has charged to the VTMRH threshold (2V typical) in order to avoid being shutdown. While VGS is less than the typical 5V threshold (VGATE-TH), the VDS start-up fault delay time is calculated from: 30104229 FIGURE 7. Setting the VDS Threshold TURN-ON TIME To slow down the output rise time a capacitor from the GATE pin to GND may be added. The turn on time depends on the threshold level of the N-Channel MOSFET, the gate capacitance of the MOSFET as well as the optional capacitance from the GATE pin to GND. Figure 8 shows the slow down capacitor C1. Reducing the turn-on time allows the MOSFET (Q1), to slowly charge a large load capacitance. Special care must be taken to keep the MOSFET within its safe operating area. If the MOSFET turns on too slow, the peak power losses may damage the device. Where ITMRL is typically 6 μA and VTMRH is typically 2V. If the CTIMER value is 68 nF (0.068μF) the VGS start-up fault delay time would typically be: VDS Fault Delay = ((2V x 0.068 μF) / 6 μA) = 23 ms When the LM5060 has successfully completed the start-up sequence by reaching a VGS of 5V within the fault delay time set by the timer capacitor (CTIMER), the capacitor is quickly discharged to 300mV (typical) and the charge current is increased to 11 μA (typical) while the gate of the external MOSFET is continued to be charge at a 24 μA (typical) rate. The external MOSFET may not be fully enhanced at this point in time and some additional time may be needed to allow the gate-to-source voltage (VGS) to charge to a higher value. The drain-to-source voltage (VDS) of the external MOSFET must fall below the VDSTH threshold set by RS and ISENSE before the timer capacitor has charged to the VTMRH threshold (2V typical) to avoid a fault. When VGS is greater than the typical 5V threshold (VGATETH), the VDS transition fault delay time is calculated from: www.national.com 16 LM5060 Where ITMRH is typically 11 μA, VTMRH is typically 2V, and VTMRL is typically 300 mV. If the CTIMER value is 68 nF (0.068 μF) the VDS transition fault delay time would typically be: VDS Fault Delay = (((2V-0.3V) x 0.068 μF) / 11 μA) = 10 ms Should a subsequent load current surge trip the VDS Fault Comparator, the timer capacitor discharge transistor turns OFF and the 11 μA (typical) current source begins linearly charging the timer capacitor. If the surge current, with the detected excessive VDS voltage, lasts long enough for the timer capacitor to charge to the timing comparator threshold (VTMRH) of typically 2V, the LM5060 will immediately discharge the MOSFET gate and latch the MOSFET off. The VDS fault delay time during an Over-Current event is calculated from: All trace inductances in the design including wires and printed circuit board traces will cause inductive voltage kicks during the fast termination of a conducting current. On the input side of the LM5060 circuit this inductive kick can cause large positive voltage spikes, while on the output side, negative voltage spikes are generated. To limit such voltage spikes, local capacitance or clamp circuits can be used. The necessary capacitor value depends on the steady state input voltage level, the level of current running through the MOSFET, the inductance of circuit board traces as well as the transition speed of the MOSFET. Since the exact amount of trace inductance is hard to predict, careful evaluation of the circuit board is the best method to optimize the input or output capacitance or clamp circuits. UVLO, OVP The UVLO and OVP thresholds are programmed to enable the external MOSFET (Q1) when the input supply voltage is within the desired operating range. If the supply voltage is low enough that the voltage at the UVLO pin is below the UVLO threshold, Q1 is switched off by a 2.2 mA (typical) current sink at the GATE pin, denying power to the load. The UVLO threshold has approximately 180 mV of hysteresis. If the supply voltage is high enough that the voltage at the OVP pin is above the OVP threshold, the GATE pin is pulled low with a 80 mA current sink. Hysteresis is provided for each threshold. The OVP threshold has approximately 240 mV of hysteresis. Option A: The configuration shown in Figure 9 requires three resistors (R1, R2, and R3) to set the thresholds. Where ITMRH is typically 11 μA and VTMRH is typically 2V. If the CTIMER value is 68 nF (0.068 μF) the VDS Over-Current fault delay time would typically be: VDS Fault Delay = ((2V x 0.068 μF) / 11 μA) = 12 ms Since a single capacitor is used to set the delay time for multiple fault conditions, it is likely that some compromise will need to be made between a desired delay time and a practical delay time. MOSFET SELECTION The external MOSFET (Q1) selection should be based on the following criteria: • The BVDSS rating must be greater than the maximum system voltage (VIN), plus ringing and transients which can occur at VIN when the circuit is powered on or off. • The maximum transient current rating should be based on the maximum worst case VDS fault current level. • MOSFETs with low threshold voltages offer the advantage that during turn on they are more likely to remain within their safe operating area (SOA) because the MOSFET reaches the ohmic region sooner for a given gate capacitance. • The safe operating area (SOA) of the MOSFET device and the thermal properties should be considered relative to the maximum power dissipation possible during startup or shutdown. • RDS(ON) should be sufficiently low that the power dissipation at maximum load current ((IL(MAX))2 x RDS(ON)) does not increase the junction temperature above the manufacturer’s recommendation. • If the device chosen for Q1 has a maximum VGS rating less than 16V, an external zener diode must be added from gate to source to limit the applied gate voltage. The external zener diode forward current rating should be at least 80 mA to conduct the full gate pull-down current during fault conditions. INPUT and OUTPUT CAPACITORS Input and output capacitors are not necessary in all applications. Any current that the external MOSFET conducts in the on-state will decrease very quickly as the MOSFET turns off. 17 30104231 FIGURE 9. UVLO and OVP Thresholds Set By R1, R2 and R3 The procedure to calculate the resistor values is as follows: 1. Select R1 based on current consumption allowed in the resistor divider and consideration of noise sensitivity. Values between 10 kΩ and 200 kΩ are suggested. 2. Calculate R3 with the following formula: www.national.com LM5060 3. Calculate R2 with the following formula: VINMIN is the minimum and VINMAX is the maximum input voltage of the design specification. All other variables can be found in the Electrical Characteristics table of this document. To calculate the UVLO lower threshold including its hysteresis for falling VIN, use (UVLOTH-UVLOHYS) instead of UVLOTH in the formulas above. To calculate the OVP lower threshold including hysteresis for falling VIN, use (OVPTH-OVPHYS) instead of OVPTH. With three given resistors R1, R2, and R3, the thresholds can be calculated with the formulas below: To calculate the UVLO low threshold including its hysteresis, use (UVLOTH-UVLOHYS) instead of UVLOTH in the formula above. Choose the lower OVP threshold to ensure operation up to the highest VIN voltage required (VINMAX). Select R9 based on resistive divider current consumption and noise sensitivity. Values between 10 kΩ and 200 kΩ are suggested. To calculate the OVP low threshold including hysteresis, use (OVPTH-OVPHYS) instead of OVPTH. Where the R9-R11 resistor values are known, the threshold voltages are calculated from the following: Also in these two formulas, the respective lower threshold value including the hysteresis is calculated by using (UVLOTH-UVLOHYS) instead of UVLOTH, and (OVPTH-OVPHYS) instead of OVPTH. The worst case thresholds, over the operating temperature range, can be calculated using the respective min and max values in bold font in the Electrical Characteristics . Option B: UVLO and OVP can be independently adjusted using two resistor dividers as shown in Figure 10. Also in these two formulas, the respective low value including the threshold hysteresis is calculated by using (UVLOTH-UVLOHYS) instead of UVLOTH and (OVPTH-OVPHYS) instead of OVPTH. The worst case thresholds, over the operating temperature range, can be calculated using the respective minimum and maximum values in bold font in the Electrical Characteristics . Option C: The OVP function can be disabled by grounding the OVP pin. The UVLO thresholds are set as described in Option B. POWER GOOD INDICATOR A resistor between a supply voltage and the nPGD pin limits the current into the nPGD pin in a logic low condition. A nPGD pin sink current in the range of 1 mA to 5 mA is recommended. The example in Figure 11 connects the nPGD pull-up resistor R4 to the VIN pin. Any positive supply voltage less than 65V may be used instead of VIN. 30104235 FIGURE 10. Programming the Thresholds with Resistors R8-R11 30104239 Choose the upper UVLO thresholds to ensure operation down to the lowest required operating input voltage (VINMIN). Select R11 based on resistive divider current consumption and noise sensitivity. Values between 10 kΩ and 200 kΩ are suggested. FIGURE 11. Circuitry at the nPGD Pin INPUT BYPASS CAPACITOR Some input capacitance from the VIN pin to the GND pin may be necessary to filter noise and voltage spikes from the VIN rail. If the current through Q1 in Figure 1 is very large a sudden shutdown of Q1 will cause an inductive kick across the line input and pc board trace inductance which could damage the LM5060. In order to protect the VIN pin as well as SENSE, www.national.com 18 LM5060 OVP, UVLO, and nPGD pins from harm, a larger bulk capacitor from VIN to GND may be needed to reduce the amplitude of the voltage spikes. Protection diodes or surge suppressors may also be used to limit the exposure of the LM5060 pins to voltages below their maximum operating ratings. THERMAL CONSIDERATIONS In normal operation the LM5060 dissipates very little power so that thermal design may not be very critical. The power dissipation is typically the 2 mA input current times the input voltage. If the application is driving a large capacitive load application, upon shutdown of the LM5060, the load capacitor may partially, or fully, discharge back through the LM5060 circuitry if no other loads consume the energy of the precharged load capacitor. One application example where energy is dissipated by the LM5060 is a motor drive application with a large capacitor load. When the LM5060 is turned off, the motor might also turn off such that total residual energy in the load capacitor is conducted through the OUT pin to ground. The power dissipated within the LM5060 is determined by the discharge current of 80 mA and the voltage on the load capacitor. LARGE LOAD CAPACITANCE Figure 12 shows an application with a large load capacitance CL. Assume a worst case turn off scenario where Vin remains at the same voltage as CL and RL is a high impedance. The body diode of Q1 will not conduct any current and all the charge on CL is dissipated through the LM5060 internal circuitry. The dotted line in Figure 12 shows the path of this current flow. Initially the power dissipated by the LM5060 is calculated with the formula: P = IGATE-FLT x VOUT Where IGATE-FLT is the sink current of the LM5060 gate control. In applications with a high input voltage and very large output capacitance, the discharge current can be limited by an additional discharge resistor RO in series with the OUT pin as shown in Figure 13. This resistor will influence the current limit threshold, so the value of RS will need to be readjusted. 30104241 FIGURE 13. Current Limiting Resistor RO for Special Cases If a RO resistor in the OUT path is used, the current sensing will become less accurate since RO has some variability as well as the current into the OUT pin. The OUT pin current is specified in the Electrical Characteristics section as IOUT-EN. A RO resistor design compromise for protection of the OUT pin and a maintaining VDS sensing accuracy can be achieved. See the REVERSE POLARITY PROTECTION WITH A RESISTOR for more details on how to calculate a reasonable RO value. REVERSE POLARITY PROTECTION WITH DIODES Figure 14 shows the LM5060 in an automotive application with reverse polarity protection. The second N-channel MOSFET Q2 is used to prevent the body diode of Q1 from conducting in a reverse VIN polarity situation. The zener diode D3 is used to limit VIN voltage transients which will occur when Q1 and Q2 are shut off quickly. In some applications the inductive kick is handled by input capacitors and D3 can be omitted. In reverse polarity protected applications, the input capacitors will see the reverse voltage. To avoid stressing input capacitors with reverse polarity, a transorb circuit implemented with D3 and D2 may be used. Diode D1 in Figure 14 protects the VIN pin in the event of reverse polarity. The resistor R1 protects the GATE pin from reverse currents exceeding 25 mA in the reverse polarity situation. This GATE resistor would slow down the shutdown of Q1 and Q2 dramatically. To prevent a slow turn off in fault conditions, D5 is added to bypass the current limiting resistor R1. When Q1 and Q2 are turned on, R1 does not cause any delay because the GATE pin is driven with a 24 µA current source. D6, Q3 and R2 protect Q2 from VGS damage in the event of reverse input polarity. Diodes D5 and D7 are only necessary if the output load is highly capacitive. Such a capacitive load in combination with a high reverse polarity input voltage condition can exceed the power rating of the internal zener diode between OUT pin and GATE pin as well as the internal diode between the OUT pin and SENSE pin. External diodes D5 and D7 should be used in reverse polarity protected applications with large capacitive loads. Figure 14 Example Circuit Specification Operating Voltage Range Current max OVP setting UVLO setting 19 30104240 FIGURE 12. Discharge Path of Possible Load Capacitor In applications exposed to reverse polarity on the input and a large load capacitance on the output, a current limiting resistor in series with the OUT pin is required to protect the LM5060 OUT pin from reverse currents exceeding 25 mA. Figure 13 shows the resistor RO in the trace to the OUT pin. 9V to 24V 30A 27V typical 9V typical www.national.com LM5060 30104242 FIGURE 14. Application with Reverse Polarity Protection with Diodes for OUT Pin Protection REVERSE POLARITY PROTECTION WITH A RESISTOR An alternative to using external diodes to protect the LM5060 OUT pin in the reverse polarity input condition is a resistor in series with the OUT pin. Adding an OUT pin resistor may require modification of the resistor in series with the SENSE pin. A resistor in series with the OUT pin will limit the current through the internal zener diode between OUT and GATE as well as through the diode between OUT and SENSE. The value of these resistors should be calculated to limit the current through the diode across the input terminals of the VDS fault comparator to be no more than 4 mA. Figure 15 shows the internal circuitry relevant for calculating the values of the resistor RO in the OUT path to limit the current into the OUT pin to 4 mA. 30104243 FIGURE 15. Current Limiting Resistor for Negative SENSE Condition When calculating the minimum RO resistor required to limit the current into the OUT pin, the internal current sources of 8 µA and 16 µA may be neglected. The following formulas can be used to calculate the resistor value RO(MIN) which is necessary to keep the IO current to less than 4 mA. Case A for situations where VOUT > VIN and reverse polarity situation is present. See Figure 15. VIN is negative, but the voltage at the SENSE pin can roughly be assumed to be 0.0V due to the internal diode from the SENSE pin to GND. In this case, VIN also has to be limited to a negative voltage so that reverse current through the SENSE pin does not exceed 25 mA. www.national.com 20 LM5060 30104257 FIGURE 16. Current Limiting Resistor in the OUT Path for OUT > SENSE Condition Case B for situations where VOUT > VIN and there is no reverse polarity situation present. See Figure 16. VIN is positive and VOUT is also positive, but VOUT is higher than VIN: Case C for situations where VOUT < VIN and both VIN and VOUT are positive as well. In such cases there is no risk of excessive OUT pin current. No current limiting resistors are necessary. Both the SENSE and OUT voltages should be limited to less than 65V. In this case the voltage on the SENSE pin should not exceed 65V. 30104258 FIGURE 17. Current Limiting Resistor for Negative OUT Conditions Case D for situations where VOUT < VIN, while VOUT is negative and VIN is positive. See Figure 17. RO needs to be selected to protect the OUT pin from currents exceeding 25 mA. into account. The LM5060 monitors the VDS voltage of an external N-Channel MOSFET. The VDS fault detection voltage is the drain to source voltage threshold (VDSTH). The formula below calculates a proper RS resistor value for a desired VDSTH taking into account the voltage drop across the RO resistor. FAULT DETECTION WITH RS AND RO Figure 18 shows an example circuit where the OUT pin is protected against a reverse battery situation with a current limiting resistor RO. When using resistor RO in the OUT pin path, the resistor RS has to be selected taking the RO resistor 21 VOFFSET is the offset voltage between the SENSE pin and the OUT pin, ISENSE is the threshold programming current, and www.national.com LM5060 IOUT-EN is the OUT pin bias current. When RS and RO have been selected, the following formula can be used for VDSTH min and max calculations: CIRCUIT EXAMPLE OF REVERSE POLARITY PROTECTION WITH RESISTOR Figure 18 shows an example circuit which is protected against reverse polarity using resistor R8 instead of the diodes D5 and D7 of Figure 14. Figure 14 Example Circuit Specification The MOSFET drain-to-source current threshold is: Operating Voltage Range Current max OVP setting UVLO setting 9V to 24V 30A 27V typical 9V typical Where RDS(ON) is the on resistance of the pass element Q1 in Figure 1. 30104251 FIGURE 18. Application with Reverse Polarity Protection with a Resistor for OUT Pin Protection www.national.com 22 LM5060 Physical Dimensions inches (millimeters) unless otherwise noted 10-Lead MSOP Package NS Package Number MUB10A 23 www.national.com LM5060 High-Side Protection Controller with Low Quiescent Current Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage References PowerWise® Solutions Temperature Sensors PLL/VCO www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Quality and Reliability Feedback/Support Design Made Easy Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/training Applications & Markets Mil/Aero PowerWise® Design University Serial Digital Interface (SDI) www.national.com/sdi www.national.com/wireless www.national.com/tempsensors SolarMagic™ THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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