AD8214

High Voltage Threshold Detector AD8214 FEATURES Input-to-output response: –IN. The input volt ages are reference d to t he supply volt age, as is t he internal 2.4 V regu lator. The input-to-output respons e t ime is typically 20 mV, 50 mV step 20% to 80%, ROUT = 3.3 kΩ, VOD = 5 mV, 50 mV step 20% to 80%, ROUT = 3.3 kΩ, VOD = >10 mV, 50 mV step TA = 25°C, voltage from VREG to VS TA = –40°C to +125°C 50 mV to 250 mV step 5 mV ≤ VOD ≤ 15 mV, output low to high 15 mV ≤ VOD ≤ 30 mV, output low to high VOD ≥ 30 mV, output low to high 0.8 2 5 500 VS + 0.2 20 1.2 MΩ MΩ mV V nA mA nA ns ns ns ns V % ns ns ns mV 12 1 100 90 75 110 100 2.43 ±5 90 80 75 15 INPUT-REFERRED DYNAMIC ERROR2 POWER SUPPLY Operating Range Maximum Voltage Minimum Voltage Output Voltage Range3 Supply Current TEMPERATURE RANGE FOR SPECIFIED PERFORMANCE 1 2 3 GND to VS GND to VS With respect to VREG Output low Output high 65 5 2 240 1.2 −40 +125 62.5 V V V µA mA °C VOD represents the overdrive voltage, or the amount of voltage by which the threshold point has been exceeded. See the Input-Referred Dynamic Error section. The voltage at OUT must not be allowed to exceed the VREG voltage, which is always 2.4 V less than the supply. For example, when the supply voltage is 5 V and the output current is 1 mA, the load resistor must not be more than (5 V – 2.4 V)/{1 mA × (1 + 20%)}, or 2.17 kΩ, to ensure the signal does not exceed 2.6 V. As the supply increases, the output signal also can be increased, by the same amount. Rev. 0 | Page 3 of 16 AD8214 ABSOLUTE MAXIMUM RATINGS TA = –40°C to +125°C Table 2. Parameter Supply Voltage Continuous Input Voltage Reverse Supply Voltage Operating Temperature Range Storage Temperature Range Output Short-Circuit Duration Rating 65 V 68 V 0.3 V −40°C to +125°C −65°C to +150°C Indefinite ESD CAUTION Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only ; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Rev. 0 | Page 4 of 16 AD8214 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 1 6 8 2 VS 1 +IN 2 AD8214 8 –IN 06193-007 NC = NO CONNECT Figure 2. Metallization Diagram Figure 3. Pin Configuration Table 3. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 Mnemonic VS +IN VREG NC OUT GND NC –IN X –196 –198 –196 +196 +196 –31 Y +447 –58 –346 –348 +447 +449 Description Supply Voltage. Noninverting Input. Regulator Voltage. No Connect. Output. Ground. No Connect. Inverting Input. Rev. 0 | Page 5 of 16 06193-002 3 5 7 NC TOP VIEW VREG 3 (Not to Scale) 6 GND NC 4 5 OUT AD8214 TYPICAL PERFORMANCE CHARACTERISTICS 16 0 INPUT OFFSET VOLTAGE (mV) 15 INPUT BIAS CURRENT (nA) –0.4 14 5V –0.8 13 65V –1.2 12 11 06193-041 –1.6 06193-035 10 –1.2 –1.0 –0.8 –0.6 –0.4 –0.2 0 0.2 –2.0 –0.9 –0.8 –0.7 –0.6 –0.5 –0.4 –0.3 –0.2 –0.1 INPUT COMMON-MODE VOLTAGE (V) 0 0.1 0.2 INPUT COMMON-MODE VOLTAGE (V) Figure 4. Input Bias Current vs. Input Common-Mode Voltage (With Respect to VS) Figure 7. Input Offset Voltage vs. Input Common-Mode Voltage (With Respect to VS) 280 1.11 1.09 OUTPUT CURRENT (mA) 270 SUPPLY CURRENT (µA) TA = –40°C 1.07 1.05 1.03 1.01 0.99 0.97 –1.40 260 TA = +25°C 250 240 TA = +125°C 230 06193-024 –1.15 –0.90 –0.65 –0.40 –0.15 0.10 220 5 15 25 35 45 55 65 INPUT COMMON-MODE VOLTAGE (V) SUPPLY VOLTAGE (V) Figure 5. Output Current (Output High) vs. Input Common-Mode Voltage (With Respect to VS) 4 1.25 1.24 INPUT OFFSET VOLTAGE (mV) SUPPLY CURRENT (mA) Figure 8. Supply Current vs. Supply Voltage (Output Low) TA = –40°C 2 1.23 1.22 TA = +25°C 1.21 1.20 1.19 1.18 TA = +125°C 0 –2 06193-018 –4 –40 –25 –10 5 20 35 50 65 80 95 110 125 5 15 25 35 45 55 65 TEMPERATURE (°C) SUPPLY VOLTAGE (V) Figure 6. Input Offset Voltage vs. Temperature Figure 9. Supply Current vs. Supply Voltage (Output High) Rev. 0 | Page 6 of 16 06193-034 06193-023 AD8214 2.448 1.10 REGULATOR VOLTAGE (V) 2.444 OUTPUT CURRENT (mA) 1.05 TA = +125°C TA = +25°C 2.440 TA = +125°C 1.00 TA = –40°C 2.436 TA = +25°C 2.432 TA = –40°C 06193-022 0.95 06193-020 2.428 5 15 25 35 45 55 65 0.90 5 15 25 35 45 55 65 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) Figure 10. Regulator Voltage vs. Supply Voltage (Between VREG and VS) 2.50 12.0 11.5 Figure 13. Output Current vs. Supply Voltage (Output High) 2.45 HYSTERESIS VOLTAGE (mV) 06193-021 REGULATOR VOLTAGE (V) TA = +125°C TA = +25°C 11.0 10.5 10.0 9.5 9.0 06193-017 2.40 TA = –40°C 2.35 8.5 8.0 –40 2.30 10 50 100 1 50 200 –25 –10 5 20 35 50 65 80 95 110 125 REGULATOR LOAD RESISTANCE (kΩ) TEMPERATURE (°C) Figure 11. Regulator Voltage vs. Regulator Load Resistance (Series Resistance Between VREG and VS) 700 600 OUTPUT CURRENT (nA) 170 Figure 14. Hysteresis Voltage vs. Temperature (–IN Increasing) ROUT = 5kΩ 150 TA = +125°C 500 400 300 200 100 0 TA = +25°C TA = –40°C 5 15 25 35 45 55 06193-019 FALL TIME (ns) 130 110 ROUT = 3.3kΩ 90 70 06193-027 65 50 15 25 35 45 55 65 75 85 95 SUPPLY VOLTAGE (V) OVERDRIVE VOLTAGE (mV) Figure 12. Output Current vs. Supply Voltage (Output Low) Figure 15. Fall Time vs. Overdrive Voltage (–IN > +IN by Specified VOD) Rev. 0 | Page 7 of 16 AD8214 110 –IN 30mV/DIV ROUT = 5kΩ RISE TIME (ns) 90 VOD = 50mV +IN ROUT = 3.3kΩ VOD = 30mV 70 OUT 2V/DIV 06193-028 50 5 15 25 35 45 55 65 75 85 95 100ns/DIV OVERDRIVE VOLTAGE (mV) Figure 16. Rise Time vs. Overdrive Voltage (+IN > –IN by Specified VOD) Figure 19. Typical Propagation Delay (ROUT = 5 kΩ) –IN 10mV/DIV VOD = 15mV +IN –IN 50mV/DIV VOD = 100mV +IN VOD = 5mV OUT 2V/DIV VOD = 100mV OUT 2V/DIV 06193-029 06193-032 100ns/DIV 100ns/DIV Figure 17. Typical Propagation Delay (ROUT = 5 kΩ) 190 170 150 130 110 90 70 06193-030 Figure 20. Typical Propagation Delay (ROUT = 5 kΩ) –IN 10mV/DIV +IN VOD = 20mV VOD = 10mV OUT 2V/DIV PROPAGATION DELAY (ns) ROUT = 5kΩ 50 15 25 35 45 55 65 75 85 95 100ns/DIV OVERDRIVE VOLTAGE (mV) Figure 18. Typical Propagation Delay (ROUT = 5 kΩ) Figure 21. Propagation Delay vs. Overdrive Voltage (–IN > +IN by Specified VOD, Output High to Low) Rev. 0 | Page 8 of 16 06193-026 ROUT = 3.3kΩ 06193-031 AD8214 120 240 MEAN = –10 110 PROPAGATION DELAY (ns) 210 180 100 COUNT ROUT = 3.3kΩ 90 150 120 90 80 ROUT = 5kΩ 60 06193-025 70 60 5 15 25 35 45 55 65 75 85 95 0 –12.0 –11.5 OVERDRIVE VOLTAGE (mV) –11.0 –10.5 –10.0 –9.5 –9.0 HYSTERESIS VOLTAGE (mV) –8.5 –8.0 Figure 22. Propagation Delay vs. Overdrive Voltage, (+IN > –IN by Specified VOD, Output Low to High) 12 240 Figure 25. Hysteresis Voltage Distribution MEAN = 987.7 HYSTERESIS VOLTAGE (mV) 11 210 180 COUNT 10 150 120 90 60 9 8 06193-037 06193-039 30 0 800 7 –1.0 –0.9 –0.8 –0.7 –0.6 –0.5 –0.4 –0.3 –0.2 –0.1 INPUT COMMON-MODE VOLTAGE (V) 0 0.1 0.2 850 900 950 1000 1050 1100 OUTPUT CURRENT (µA) 1150 1200 Figure 23. Hysteresis Voltage vs. Input Common-Mode Voltage (With Respect to VS) 140 MEAN = –0.16 120 100 Figure 26. Output Current Distribution 160 140 120 100 MEAN = –2.42 COUNT COUNT 80 60 40 20 0 –4 80 60 40 06193-036 –3 –2 –1 0 1 2 3 4 0 –2.46 –2.45 INPUT OFFSET VOLTAGE (mV) –2.44 –2.43 –2.42 REGULATOR VOLTAGE (V) –2.41 –2.40 Figure 24. Input Offset Voltage Distribution Figure 27. Regulator Voltage Distribution (With Respect to VS) Rev. 0 | Page 9 of 16 06193-038 20 06193-040 30 AD8214 THEORY OF OPERATION The AD8214 is a high voltage comparator offering an input-tooutput response time of less than 100 ns. This device is ideal for detecting overcurrent conditions on the high side of the control loop. The AD8214 is designed specifically to facilitate and allow for fast shutdown of the control loop, preventing damage due to excessive currents to the FET, load, or shunt resistor. The AD8214 operates with a supply of 5 V to 65 V. It combines a fast comparator, optimized for high side operation, with a 2.4 V series voltage regulator. The regulator provides a stable voltage that is negative with respect to the positive supply rail, and it is intended to provide power to the internal electronics, set a comparison threshold below the supply rail, and power small application circuits used with the comparator. The differential input of the comparator may be operated at, or slightly above or below, the positive supply rail. Typically, one of the comparator inputs is driven negative with respect to the positive supply by a small series resistor carr ying the main supply current to the load. The other input of the comparator BATTERY CONSTANT THRESHOLD I + R1 _ + SHUNT VOLTAGE DROP ACROSS SHUNT CORRESPONDING TO CURRENT LEVEL TO LOAD 3 2 5 8 1 connects to a voltage divider across the regulator, so the comparator trips as the voltage across the series resistor crosses the user-selected threshold. The AD8214 features a current output. The current is low (100 nA typical), until the user selected threshold is crossed. After this point the output switches to high (1 mA typical). The current output driver complies with load voltage from 0 V to (VS – 2.4 V). The current easily drives a ground referenced resistor to develop logic levels determined by the value of the load resistor. The comparator input is balanced to switch as the inverting input (–IN) is driven negative with respect to the noninverting input (+IN). As the comparator output switches from 0 mA to 1 mA, a small hysteresis (10 mV) is activated to minimize the effects of noise in the system that may be triggered by the comparator signal. This means that to restore the output to zero, the input polarity must be reversed by 10 mV beyond the original threshold. 1 _ R2 UP TO 65V CONSTANT 2.4V 2.4V REGULATOR 2 6 3 Figure 28. Simplified Schematic Rev. 0 | Page 10 of 16 06193-005 AD8214 COMPARATOR OFFSET AND HYSTERESIS The AD8214 features built-in hysteresis to minimize the effects of noise in the system. There is also a small offset at the input of the device. values for these resistors can be chosen based on the desired threshold voltage using the equation: ⎛ 2.4 ⎞ × R1 = VTH ( + IN ) ⎟ ⎜ ⎝ R1 + R2 ⎠ (1) VOH For proper operation it is recommended that the internal 2.4 V regulator not be loaded down by using small R1 and R2 values. Figure 11 shows the proper range for the total series resistance. INPUT-REFERRED DYNAMIC ERROR VH VOL VOS = INPUT OFFSET VOLTAGE VH = HYSTERESIS VOLTAGE VTH = THRESHOLD VOLTAGE VOH = OUTPUT HIGH VOL = OUTPUT LOW VOS 06193-033 VTH Frequently, the dynamics of comparators are specified in terms of propagation delay of the response at the output to an input pulse crossing the threshold between two overload states. For this measurement, the rise time of the input pulse is negligible compared to the comparator propagation delay. In the case of the AD8214, this propagation delay is typically 100 ns, when the input signal is a fast step. The primar y purpose of the AD8214 is to monitor for overcurrent conditions in a system. It is much more common that in such systems, the current in the path increases slowly ; therefore, the transition between two input overload conditions around the threshold is slow relative to the propagation delay. In some cases, this transition can be so slow that the time from the actual threshold crossing to the output signal switching states is longer than the specified propagation delay, due to the comparator dynamics. If the voltage at the input of the AD8214 is crossing the set threshold at a rate ≤100 mV/µs, the output switches states before the threshold voltage has been exceeded by 15 mV. Therefore, if the input signal is changing so slowly that the propagation delay is affected, the error that accumulates at the input while waiting for the output response is proportionately smaller and, typically, less than 15 mV for ramp rates ≤100 mV/µs. Figure 29. Hysteresis and Input Offset Voltage Definition Figure 29 shows the relationship between the input voltage and the output current. The horizontal axis represents the voltage between the positive (+IN) and negative (–IN) inputs of the AD8214. The vertical axis shows the output current for a given input voltage. VTH represents the point where the inputs are at the same voltage level (+IN = –IN). The output of the AD8214 remains low (VOL) provided (–IN) is at a higher voltage potential than (+IN). As the input voltage transitions to +IN > –IN, the output switches states. Under ideal conditions, the output is expected to change states at exactly VTH. In practice, the output switches when the inputs are equal ± a small offset voltage (VOS). Once the output switches from low to high, it remains in this state until the input voltage falls below the hysteresis voltage. Typically, this occurs when +IN is 10 mV below –IN. SETTING THE INPUT THRESHOLD VOLTAGE The AD8214 features a 2.4 V series regulator, which can be used to set a reference threshold voltage with two external resistors. The resistors constitute a voltage divider, the middle point of which connects to +IN. The total voltage across the resistors is always 2.4 V. (See Figure 28 for proper resistor placement.) The Rev. 0 | Page 11 of 16 AD8214 APPLICATIONS TYPICAL SETUP AND CALCULATIONS The key feature of the AD8214 is its ability to detect an overcurrent condition on the high side of the rail and provide a signal in less than 100 ns. This performance protects expensive loads, FETs, and shunt resistors in a variety of systems and applications. This section details a typical application in which the normal current in the system is less ≤10 A and an overcurrent detection is necessary when 15 A is detected in the path. If we assume a shunt resistance (RSHUNT) of 0.005 Ω and a common-mode voltage range of 5 V to 65 V, the typical voltage across the shunt resistor is 10 A × 0.005 Ω = 50 mV The voltage drop across the shunt resistor, in the case of an overcurrent condition is 15 A × 0.005 Ω = 75 mV The threshold voltage, must therefore be set at 75 mV, corresponding to the overcurrent condition. R1 and R2 can be selected based on this 75 mV threshold at the positive input of the comparator. A low load current across the regulator corresponds to optimal regulator performance; therefore, the series resistance of R1 and R2 must be relatively large. For this case, the total resistance can be set as R1 + R2 = 200 kΩ To have a 75 mV drop across R1, the following calculations apply: Under normal operating conditions, the current is 10 A or less, corresponding to a maximum voltage drop across the shunt of 50 mV. This means that the negative input of the comparator is 50 mV below the batter y voltage. Since the positive input is 75 mV below the batter y voltage, the negative input is at a higher potential than the positive; therefore, the output of the AD8214 is low. If the current increases to 15 A, the drop across the shunt is 75 mV. As the current continues to increase, the positive input of the comparator reaches a higher potential than the negative, and the output of the AD8214 switches from low to high. The input-to-output response of the AD8214 is less than 100 ns. The output resistor in this case is selected so that the logic level high signal is 3.3 V. The output changes states from low to high in the case of an overcurrent condition. However, the input offset voltage is typically 1 mV; therefore, this must be taken into consideration when choosing the threshold voltage. When the current in the system drops back down to normal levels, the AD8214 changes states from high to low. However, due to the built-in 10 mV hysteresis, the voltage at (–IN) must be 10 mV higher than the threshold for the output to change states from high to low. This built-in hysteresis is intended to prevent input chatter as well as any false states. Table 4 shows typical resistors combinations that can be used to set an input threshold voltage. Numbers are based on a 2.43 V VREG. Table 4. Threshold (mV ) 30 50 60 75 110 R1 (kΩ) 1.5 1.6 2 2.4 8.06 R2 (kΩ) 120 75 80 75 169 2.4V = 12 µA 200 kΩ 75 mV = 6.25 kΩ = R1 12 µA R2 = (200 kΩ – R1) = 193.75 kΩ The values for R1 and R2 are set; correspondingly, the threshold voltage at +IN is set at 75 mV. BATTERY I C1 0.01µF RSHUNT (0.005Ω) ILOAD R2 193.75kΩ R1 6.25kΩ 2 5 8 1 IOUT VOUT ROUT = 3.3kΩ 2.4V REGULATOR 3 6 06193-006 Figure 30. Typical Application Rev. 0 | Page 12 of 16 AD8214 HIGH SIDE OVERCURRENT DETECTION The AD8214 is useful for many automotive applications using the load configuration shown in Figure 31. Because the part powers directly from the battery voltage, the shunt resistor must be on the high side. The AD8214 monitors the current in the path as long as the battery voltage is between 5 V and 65 V. If the current reaches an undesirable level that corresponds to the user-selected threshold, the output of the AD8214 switches states in less than 100 ns. The microcontroller, analog-to-digital converter, or FET driver can be directly notified of this condition. I SHUNT CLAMP DIODE BATTERY UP TO 65V AD8214 C1 R1 R2 3 4 1 2 SWITCH –IN 8 NC 7 VS +IN VREG NC GND 6 06193-004 OUT 5 OVERCURRENT DETECTION (