19-1348; Rev 0; 4/98 Precision Shunt Regulators with Reset in SOT23-3 ____________________________Features ♦ 100µA to 50mA Shunt Current Range ________________________Applications _______________Ordering Information ♦ Low Cost ♦ 3-Pin SOT23 Package ♦ ±1.5% Tolerance on Output Voltage ♦ Three Shunt Voltages Available: 5V, 3.3V, 3.0V ♦ Precision Power-On Reset Threshold: 1.5% Tolerance Available with Either RESET (MAX6331) or RESET (MAX6330) Outputs ♦ 140ms Reset Timeout Period—No External Components Required PART* TEMP. RANGE PIN-PACKAGE MAX6330_UR-T MAX6331_UR-T -40°C to +85°C -40°C to +85°C 3 SOT23-3 3 SOT23-3 Controllers Household Appliances Intelligent Instruments Critical µP and µC Power Monitoring Portable/Size-Sensitive Equipment Automotive SOT RESET SHUNT TOP MARK SUFFIX THRESHOLD REGULATOR (V) VOLTAGE (V) MAX6330 MAX6331 ____________Typical Operating Circuit VIN RS IIN *Insert the desired suffix letter (from the table below) into the blank to complete the part number. These devices have a minimum order increment of 2,500 pieces. VSHUNT 4.63 3.06 5.0 3.3 EKAA EMAA ELAA ENAA S 2.78 3.0 EDAA EPAA ___________________Pin Configuration ILOAD TOP VIEW CL 0.1µF* ISHUNT L T VCC SHUNT MAX6330 MAX6331 RESET (RESET) µP GND 1 RESET INPUT GND MAX6330 MAX6331 GND 3 SHUNT RESET 2 (RESET) SOT23-3 *SEE THE SECTION CHOOSING THE BYPASS CAPACITOR (CL) ( ) ARE FOR THE MAX6331 ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX6330/MAX6331 ________________General Description The MAX6330/MAX6331 combine a precision shunt regulator with a power-on reset function in a single SOT23-3 package. They offer a low-cost method of operating small microprocessor (µP)-based systems from high-voltage sources, while simultaneously protecting µPs from power-up, power-down, and brownout conditions. Both active-low (MAX6330) and active-high (MAX6331) push/pull output versions are available. The output voltage has ±1.5% tolerance. The MAX6330/MAX6331 operate over a wide shunt current range from 100µA to 50mA, and offer very good transient immunity. A 3-pin SOT23 package allows for a significant reduction in board space and improves reliability compared to multiple-IC/discrete solutions. These devices have a minimum order increment of 2,500 pieces. MAX6330/MAX6331 Precision Shunt Regulators with Reset in SOT23-3 ABSOLUTE MAXIMUM RATINGS Terminal Voltage (with respect to GND), All Pins Except SHUNT....................-0.3V to (VSHUNT + 0.3V) Input Current (ISHUNT) ........................................................60mA Output Current (RESET/RESET)..........................................20mA Short-Circuit Duration.................................................Continuous Continuous Power Dissipation SOT23-3 (derate 4mW/°C above +70°C)....................320mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°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 (ISHUNT = 1mA, CL = 0.1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MAX633_L VSHUNT Regulation Voltage (Note 1) VSHUNT ISHUNT = 0.1mA to 50mA MAX633_T MAX633_S Minimum VSHUNT for which RESET is Valid (MAX6330) MIN TYP MAX TA = +25°C 4.93 5.0 5.07 TA = -40°C to +85°C 4.85 TA = +25°C 3.25 TA = -40°C to +85°C 3.20 TA = +25°C 2.96 TA = -40°C to +85°C 2.91 TA = 0°C to +70°C 1.0 TA = -40°C to +85°C 1.2 VSHUNT Tempco Minimum Shunt Current (Note 2) ISHUNT(min) Maximum Shunt Current (Note 3) ISHUNT(max) 100 Reset Threshold Voltage VTH MAX633_T MAX633_S TA = +25°C 4.56 TA = -40°C to +85°C 4.50 TA = +25°C 3.01 TA = -40°C to +85°C 2.97 TA = +25°C 2.74 TA = -40°C to +85°C 2.70 Reset Threshold Tempco VSHUNT to Reset Delay Reset Pulse Width 2 5.15 3.3 3.35 3.40 3.0 100mV overdrive, CL = 15pF 100 V 3.04 3.09 V 40 ppm/°C 60 µA 50 MAX633_L UNITS 4.63 4.69 3.06 3.11 mA 4.75 3.15 2.78 V 2.82 2.86 40 ppm/°C 20 µs 140 _______________________________________________________________________________________ 200 ms Precision Shunt Regulators with Reset in SOT23-3 MAX6330/MAX6331 ELECTRICAL CHARACTERISTICS (continued) (ISHUNT = 1mA, CL = 0.1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS ISINK = 3.2mA ISINK = 1.2mA RESET/RESET Output Voltage Low (Note 4) VOL VOH TYP MAX MAX6330T/S, VTH(min) 0.3 MAX6331T/S, VTH(max) V 0.3 MAX6330, VSHUNT = 1.2V, ISINK = 50µA, TA = -40°C to +85°C 0.3 ISOURCE = 500µA MAX6331L, VTH(min) MAX6330L, VTH(max) MAX6331T/S, VTH(min) MAX6330T/S, VTH(max) MAX6331, 1.8V < VSHUNT < VTH(min), ISOURCE = 150µA UNITS 0.4 MAX6331L, VTH(max) MAX6330, VSHUNT = 1V, ISINK = 50µA, TA = 0°C to +70°C ISOURCE = 800µA RESET/RESET Output Voltage High (Note 4) MIN MAX6330L, VTH(min) 0.8 x VSHUNT 0.8 x VSHUNT V 0.8 x VSHUNT Note 1: It is recommended that the regulation voltage be measured using a 4-wire force-sense technique when operating at high shunt currents. For operating at elevated temperatures, the device must be derated based on a +150°C maximum allowed junction temperature and a maximum thermal resistance of 0.25°C/mW junction to ambient when soldered on a printed circuit board. The TA = +25°C specification over load is measured using a pulse test at 50mA with less than 5ms on time. Note 2: Minimum shunt current required for regulated VSHUNT. Note 3: Maximum shunt current required for regulated VSHUNT. Note 4: In a typical application where SHUNT serves as the system voltage regulator, note that both ISOURCE for VOH and ISINK for VOL come from VSHUNT (see the Typical Operating Circuit). _______________________________________________________________________________________ 3 __________________________________________Typical Operating Characteristics (Typical Operating Circuit, CL = 0.1µF, ILOAD = 0mA, TA = +25°C, unless otherwise noted.) NORMALIZED SHUNT VOLTAGE vs. TEMPERATURE TA = +25°C 1.000 TA = -40°C 0.995 TA = +85°C ISHUNT = 50mA ISHUNT = 25mA 1.000 ISHUNT = 1mA 0.995 40 MAX6330 TOC5 MAX6330 TOC02 1.005 NORMALIZED SHUNT VOLTAGE MAX6330 TOC01 1.005 SHUNT VOLTAGE OVERSHOOT vs. BYPASS CAPACITANCE (CL) SHUNT VOLTAGE OVERSHOOT (mV) NORMALIZED SHUNT VOLTAGE vs. SHUNT CURRENT NORMALIZED SHUNT VOLTAGE 35 ISHUNT = 5mA TO 50mA 30 25 ISHUNT = 0.1mA TO 5mA 20 15 10 ISHUNT = 1mA TO 1mA 5 0.990 0.990 0.1 1 10 0 -40 50 -20 0 20 40 60 80 POWER-UP RESET TIMEOUT vs. TEMPERATURE 1.005 1.000 0.995 0.990 MAX6330 TOC03 160 POWER-UP RESET TIMEOUT (ms) MAX6330 TOC04 NORMALIZED RESET THRESHOLD 1.010 150 140 130 120 110 100 -40 -20 0 20 40 60 80 -40 -20 0 20 40 TEMPERATURE (°C) TEMPERATURE (°C) STABILITY BOUNDARY CONDITIONS START-UP TRANSIENT MAX6330 TOC06 50 RECOMMENDED CAPACITOR OPERATING REGION UNSTABLE REGION 40 20 0.1 LOAD CAPACITANCE (µF) NORMALIZED RESET THRESHOLD vs. TEMPERATURE 30 0.0047 0.01 TEMPERATURE (°C) SHUNT CURRENT (mA) RS = 15kΩ VIN 50V/div RECOMMENDED CAPACITOR VSHUNT 2V/div RECOMMENDED CAPACITANCE 10 60 0 1 0.001 0.01 0.1 1 LOAD CAPACITANCE (µF) 4 _______________________________________________________________________________________ 80 MAX6330 TOC07 0.01 SHUNT CURRENT (mA) MAX6330/MAX6331 Precision Shunt Regulators with Reset in SOT23-3 1 Precision Shunt Regulators with Reset in SOT23-3 PIN NAME FUNCTION MAX6330 MAX6331 1 1 GND Ground 2 — RESET Inverting Reset Output. RESET remains low while VSHUNT is below the reset threshold and for 140ms after VSHUNT rises above the threshold. — 2 RESET Noninverting Reset Output. RESET remains high while VSHUNT is below the reset threshold and for 140ms after VSHUNT rises above the threshold. 3 3 SHUNT Regulated Shunt Voltage (+5V, +3.3V, or +3.0V) _______________Detailed Description Reset Output A microprocessor’s (µP’s) reset input starts the µP in a known state. The MAX6330/MAX6331 µP supervisory circuits assert reset to prevent code-execution errors during power-up, power-down, or brownout conditions. RESET is guaranteed to be a logic low for VSHUNT > 1V. Once V SHUNT exceeds the reset threshold, an internal timer keeps RESET low for the reset timeout period; after this interval, RESET goes high. If a brownout condition occurs (VSHUNT dips below the reset threshold), RESET goes low. When VSHUNT falls below the reset threshold, the internal timer resets to zero and RESET goes low. The internal timer starts after VSHUNT returns above the reset threshold, and RESET then remains low for the reset timeout period. The MAX6331 has an active-high RESET output that is the inverse of the MAX6330’s RESET output. Consider the following information when choosing the external resistor RS: 1) The input voltage range, (VIN) 2) The regulated voltage, (VSHUNT) 3) The output current range, (ILOAD) Choose RS as follows: (VIN(max) - VSHUNT (min)) / (50mA + ILOAD(min)) ≤ RS ≤ (VIN(min) - VSHUNT (max)) / (100µA + ILOAD(max)) Choose the largest nominal resistor value for RS that gives the lowest current consumption. Provide a safety margin to incorporate the worst-case tolerance of the IIN RS VSHUNT ILOAD VIN ISHUNT CL SHUNT Shunt Regulator The shunt regulator consists of a pass device and a controlling circuit, as illustrated in Figure 1. The pass device allows the regulator to sink current while regulating the desired output voltage within a ±1.5% tolerance. The shunt current range (ISHUNT) is 100µA to 50mA. The pass transistor in the MAX6330/MAX6331 maintains a constant output voltage (VSHUNT) by sinking the necessary amount of shunt current. When ILOAD (see Typical Operating Circuit) is at a maximum, the shunt current is at a minimum, and vice versa: IIN = ISHUNT + ILOAD = (VIN - VSHUNT) / RS RESET GENERATOR 140ms TIMEOUT RESET (RESET) MAX6330 MAX6331 1.2V GND ( ) ARE FOR MAX6331 Figure 1. Functional Diagram _______________________________________________________________________________________ 5 MAX6330/MAX6331 ______________________________________________________________Pin Description _____________Applications Information Negative-Going VSHUNT Transients In addition to issuing a reset to the µP during power-up, power-down, and brownout conditions, the MAX6330/ MAX6331 are relatively immune to short-duration negative-going V SHUNT transients (glitches). Additional bypass filter capacitance mounted close to the SHUNT pin provides additional transient immunity. Choosing the Bypass Capacitor, CL The bypass capacitor (CL) on the SHUNT pin can significantly affect the device’s load-transient response, so choose it carefully. When a load transient occurs, the current for this load is diverted from the shunt regulator. The maximum load current that can be diverted from the regulator is: ILOAD (diverted from regulator) = ISHUNT(max) - ISHUNT(min) = 50mA - 100µA = 49.9mA The shunt regulator has a finite response to this transient. The instantaneous requirements of the load change are met by the charge on CL, resulting in overshoot/undershoot on VSHUNT. The magnitude of this overshoot/undershoot increases with I SHUNT and decreases with CL. When VSHUNT undershoots, the shunt current decreases to where it will only draw quiescent current (IQ), and the shunt element turns off. At this point, VSHUNT will slew toward VIN at the following rate: ∆VSHUNT / ∆t = (IIN - ILOAD - 60µA) / CL As VSHUNT rises, it will turn on the shunt regulator when it can sink 100µA of current. A finite response time for the shunt regulator to start up will result in a brief overshoot of VSHUNT before it settles into its regulation voltage. Therefore, ILOAD should always be 100µA or more below IIN, or VSHUNT will not recover to its regulation point. To prevent this condition, be sure to select the correct series-resistor R S value (see the Shunt Regulator section). Figures 2, 3, and 4 show load-transient responses for different choices of bypass capacitors on V SHUNT . These photos clearly illustrate the benefits and drawbacks of the capacitor options. A smaller bypass 6 ILOAD 2mA/div IIN = 2mA, ILOAD = 0 to 1.9mA VSHUNT IS AC COUPLED 0 0 VSHUNT 20mV/div Figure 2. Load-Transient Response with CL = 0.22µF ILOAD 2mA/div IIN = 2mA, ILOAD = 0 to 1.9mA, VSHUNT IS AC COUPLED MAX6330 FIG 03 PR = IIN(VIN(max) - VSHUNT) = I2INRS = (VIN(max) - VSHUNT)2 / RS MAX6330 FIG 02 resistor used. Ensure that the resistor’s power rating is adequate, using the following general power equation: 0 0 VSHUNT 20mV/div Figure 3. Load-Transient Response with CL = 0.033µF ILOAD 2mA/div IIN = 2mA, ILOAD = 0 to 1.9mA VSHUNT IS AC COUPLED MAX6330 FIG 04 MAX6330/MAX6331 Precision Shunt Regulators with Reset in SOT23-3 0 0 VSHUNT 20mV/div Figure 4. Load-Transient Response with CL = 0.0047µF _______________________________________________________________________________________ Precision Shunt Regulators with Reset in SOT23-3 Adding Hysteresis In certain circumstances, the MAX6330 can be trapped in a state that forces it to enter into and exit from a reset condition indefinitely. This usually occurs in systems where VSHUNT is just below the device’s trip threshold and the system draws less quiescent current under reset conditions than when operating out of reset. The difference in supply current when the device is in or out of reset can translate to a significant change in the voltage drop across RS, which the MAX6330’s built-in hysteresis may not overcome. A 100kΩ pull-up resistor will overcome this condition and add hysteresis (Figure 5). Note that adding this pull-up resistor to the MAX6330 will render RESET invalid with VSHUNT < 1V, since this output loses sinking capability at this point, and the pull-up resistor would invalidate the signal. This does not present a problem in most applications, since most µPs and other circuitry are inoperative when VSHUNT is below 1V. Interfacing to µPs with Bidirectional Reset Pins Microprocessors with bidirectional reset pins (such as the Motorola 68HC11 series) can contend with MAX6330’s reset output. If, for example, the MAX6330’s RESET output is asserted high and the µP wants to pull it low, indeterminate logic levels may result. To correct this, connect a 4.7kΩ resistor between the RESET output and the µP reset I/O (Figure 6). Buffer the RESET output to other system components. Also, RS must be sized to compensate for additional current drawn by the µP during the fault condition. Shunt Current Effects on VSHUNT and VTH When sinking large shunt currents, power dissipation heats the die to temperatures greater than ambient. This may cause the VSHUNT and V TH tolerances to approach ±3% at high ambient temperatures and high shunt currents. Limit the die temperature to less than +150°C using ΘJA = 0.25°C/mW. ___________________Chip Information TRANSISTOR COUNT: 283 RS VIN RS CL TO OTHER SYSTEM COMPONENTS VSHUNT VIN RHYST 100k CL SHUNT VCC MAX6330 µP VCC SHUNT RESET MAX6330 MAX6331 RESET INPUT µP 4.7k RESET (RESET) GND GND GND GND ( ) ARE FOR MAX6331 Figure 5. Adding Hysteresis to the MAX6330 Figure 6. Interfacing to µPs with Bidirectional Reset I/O _______________________________________________________________________________________ 7 MAX6330/MAX6331 capacitor allows a sharper drop in VSHUNT when the load transient occurs, and will suffer from a steeper overshoot when the device re-enters regulation. On the other hand, the increased compensation on a larger bypass capacitor will lead to a longer recovery time to regulation. The Typical Operating Characteristics graph Overshoot vs. Bypass Capacitance (CL) illustrates this trade-off. If the compensation of the bypass capacitor chosen is insufficient, the output (VSHUNT) can oscillate. Before choosing a bypass capacitor for the desired shunt current, observe the stability boundary conditions indicated in the Typical Operating Characteristics. The minimum output capacitance is 0.03µF to ensure stability over the full load-current range. Precision Shunt Regulators with Reset in SOT23-3 SOTPO3L.EPS MAX6330/MAX6331 Package Information 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. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.