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19-1348; Rev 0; 4/98
Precision Shunt Regulators with Reset in SOT23-3
________________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 (P)-based systems from high-voltage sources, while simultaneously protecting Ps 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 100A 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.
____________________________Features
o 100A to 50mA Shunt Current Range o Low Cost o 3-Pin SOT23 Package o 1.5% Tolerance on Output Voltage o Three Shunt Voltages Available: 5V, 3.3V, 3.0V o Precision Power-On Reset Threshold: 1.5% Tolerance Available with Either RESET (MAX6331) or RESET (MAX6330) Outputs o 140ms Reset Timeout Period--No External Components Required
MAX6330/MAX6331
________________________Applications
Controllers Household Appliances Intelligent Instruments Critical P and C Power Monitoring Portable/Size-Sensitive Equipment Automotive
_______________Ordering Information
PART* MAX6330_UR-T MAX6331_UR-T TEMP. RANGE -40C to +85C -40C to +85C PIN-PACKAGE 3 SOT23-3 3 SOT23-3
*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.
SOT RESET SHUNT TOP MARK SUFFIX THRESHOLD REGULATOR (V) VOLTAGE (V) MAX6330 MAX6331 L T S 4.63 3.06 2.78 5.0 3.3 3.0 EKAA EMAA EDAA ELAA ENAA EPAA
____________Typical Operating Circuit
VIN
RS IIN
VSHUNT ISHUNT SHUNT
ILOAD CL 0.1F* VCC
___________________Pin Configuration
TOP VIEW
MAX6330 MAX6331
RESET (RESET) GND
P
RESET INPUT
GND 1
MAX6330 MAX6331
GND RESET 2 (RESET)
3
SHUNT
SOT23-3
*SEE THE SECTION CHOOSING THE BYPASS CAPACITOR (CL) ( ) ARE FOR THE MAX6331
________________________________________________________________ Maxim Integrated Products
1
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Precision Shunt Regulators with Reset in SOT23-3 MAX6330/MAX6331
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 +70C)....................320mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
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 = 0.1F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) 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) VSHUNT Tempco Minimum Shunt Current (Note 2) Maximum Shunt Current (Note 3) ISHUNT(min) ISHUNT(max) MAX633_L Reset Threshold Voltage VTH MAX633_T MAX633_S Reset Threshold Tempco VSHUNT to Reset Delay Reset Pulse Width 100mV overdrive, CL = 15pF 100 TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C 4.56 4.50 3.01 2.97 2.74 2.70 40 20 140 200 2.78 3.06 4.63 100 TA = 0C to +70C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C MIN 4.93 4.85 3.25 3.20 2.96 2.91 1.0 1.2 40 60 50 4.69 4.75 3.11 3.15 2.82 2.86 ppm/C s ms V 3.0 3.3 TYP 5.0 MAX 5.07 5.15 3.35 3.40 3.04 3.09 V ppm/C A mA V UNITS
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Precision Shunt Regulators with Reset in SOT23-3
ELECTRICAL CHARACTERISTICS (continued)
(ISHUNT = 1mA, CL = 0.1F, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER SYMBOL ISINK = 3.2mA ISINK = 1.2mA RESET/RESET Output Voltage Low (Note 4) VOL CONDITIONS MAX6330L, VTH(min) MAX6331L, VTH(max) MAX6330T/S, VTH(min) MAX6331T/S, VTH(max) MIN TYP MAX 0.4 0.3 V 0.3 0.3 0.8 x VSHUNT 0.8 x VSHUNT 0.8 x VSHUNT V UNITS
MAX6330/MAX6331
MAX6330, VSHUNT = 1V, ISINK = 50A, TA = 0C to +70C MAX6330, VSHUNT = 1.2V, ISINK = 50A, TA = -40C to +85C ISOURCE = 800A MAX6331L, VTH(min) MAX6330L, VTH(max) MAX6331T/S, VTH(min) MAX6330T/S, VTH(max)
RESET/RESET Output Voltage High (Note 4)
VOH
ISOURCE = 500A
MAX6331, 1.8V < VSHUNT < VTH(min), ISOURCE = 150A
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 +150C maximum allowed junction temperature and a maximum thermal resistance of 0.25C/mW junction to ambient when soldered on a printed circuit board. The TA = +25C 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).
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Precision Shunt Regulators with Reset in SOT23-3 MAX6330/MAX6331
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit, CL = 0.1F, ILOAD = 0mA, TA = +25C, unless otherwise noted.)
NORMALIZED SHUNT VOLTAGE vs. SHUNT CURRENT
MAX6330 TOC01
NORMALIZED SHUNT VOLTAGE vs. TEMPERATURE
MAX6330 TOC02
SHUNT VOLTAGE OVERSHOOT vs. BYPASS CAPACITANCE (CL)
35 30 25 20 15 10 5 ISHUNT = 1mA TO 1mA ISHUNT = 0.1mA TO 5mA ISHUNT = 5mA TO 50mA
MAX6330 TOC5
1.005 NORMALIZED SHUNT VOLTAGE
1.005 ISHUNT = 50mA NORMALIZED SHUNT VOLTAGE ISHUNT = 25mA 1.000 ISHUNT = 1mA 0.995
40 SHUNT VOLTAGE OVERSHOOT (mV)
TA = +25C 1.000
TA = -40C 0.995 TA = +85C
0.990 0.01 0.1 1 10 50 SHUNT CURRENT (mA)
0.990 -40 -20 0 20 40 60 80 TEMPERATURE (C)
0 0.0047 0.01 0.1 LOAD CAPACITANCE (F) 1
NORMALIZED RESET THRESHOLD vs. TEMPERATURE
MAX6330 TOC04
POWER-UP RESET TIMEOUT vs. TEMPERATURE
MAX6330 TOC03
1.010 NORMALIZED RESET THRESHOLD
160 POWER-UP RESET TIMEOUT (ms) 150 140 130 120 110 100
1.005
1.000
0.995
0.990 -40 -20 0 20 40 60 80 TEMPERATURE (C)
-40
-20
0
20
40
60
80
TEMPERATURE (C)
STABILITY BOUNDARY CONDITIONS
MAX6330 TOC06
START-UP TRANSIENT
RS = 15k
MAX6330 TOC07
50
RECOMMENDED CAPACITOR OPERATING REGION UNSTABLE REGION
40 SHUNT CURRENT (mA)
30
VIN 50V/div
20
RECOMMENDED CAPACITOR
10
RECOMMENDED CAPACITANCE
VSHUNT 2V/div 0
1 0.001 0.01 0.1 1 LOAD CAPACITANCE (F)
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Precision Shunt Regulators with Reset in SOT23-3
______________________________________________________________Pin Description
PIN NAME MAX6330 MAX6331 1 2 -- 3 1 -- 2 3 GND RESET RESET SHUNT Ground Inverting Reset Output. RESET remains low while VSHUNT is below the reset threshold and for 140ms after VSHUNT rises above the threshold. Noninverting Reset Output. RESET remains high while VSHUNT is below the reset threshold and for 140ms after VSHUNT rises above the threshold. Regulated Shunt Voltage (+5V, +3.3V, or +3.0V) FUNCTION
MAX6330/MAX6331
_______________Detailed Description
Reset Output A microprocessor's (P's) reset input starts the P in a known state. The MAX6330/MAX6331 P 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)) / (100A + 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 VIN
RS ISHUNT
VSHUNT
ILOAD 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 100A 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
GND ( ) ARE FOR MAX6331 RESET GENERATOR 140ms TIMEOUT
RESET (RESET)
MAX6330 MAX6331
1.2V
Figure 1. Functional Diagram
_______________________________________________________________________________________ 5
Precision Shunt Regulators with Reset in SOT23-3 MAX6330/MAX6331
resistor used. Ensure that the resistor's power rating is adequate, using the following general power equation: PR = IIN(VIN(max) - VSHUNT) = I2INRS = (VIN(max) - VSHUNT)2 / RS
ILOAD 2mA/div 0 IIN = 2mA, ILOAD = 0 to 1.9mA VSHUNT IS AC COUPLED
MAX6330 FIG 02 MAX6330 FIG 04 MAX6330 FIG 03
_____________Applications Information
Negative-Going VSHUNT Transients In addition to issuing a reset to the P 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 - 100A = 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 - 60A) / CL As VSHUNT rises, it will turn on the shunt regulator when it can sink 100A 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 100A 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
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0 VSHUNT 20mV/div
Figure 2. Load-Transient Response with CL = 0.22F
ILOAD 2mA/div 0
IIN = 2mA, ILOAD = 0 to 1.9mA, VSHUNT IS AC COUPLED
0 VSHUNT 20mV/div
Figure 3. Load-Transient Response with CL = 0.033F
ILOAD 2mA/div 0
IIN = 2mA, ILOAD = 0 to 1.9mA VSHUNT IS AC COUPLED
0 VSHUNT 20mV/div
Figure 4. Load-Transient Response with CL = 0.0047F
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Precision Shunt Regulators with Reset in SOT23-3
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 0.03F to ensure stability over the full load-current range. 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 Ps and other circuitry are inoperative when VSHUNT is below 1V.
MAX6330/MAX6331
Interfacing to Ps 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 P wants to pull it low, indeterminate logic levels may result. To correct this, connect a 4.7k resistor between the RESET output and the P 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 P during the fault condition.
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 100k pull-up resistor will overcome this condition and add hysteresis (Figure 5).
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 +150C using JA = 0.25C/mW.
___________________Chip Information
TRANSISTOR COUNT: 283
RS VIN CL RHYST 100k VCC SHUNT VIN CL RS VSHUNT
TO OTHER SYSTEM COMPONENTS
SHUNT
VCC
MAX6330
RESET RESET INPUT
P
MAX6330 MAX6331
RESET (RESET)
P
4.7k
GND
GND GND GND
( ) ARE FOR MAX6331
Figure 5. Adding Hysteresis to the MAX6330
Figure 6. Interfacing to Ps with Bidirectional Reset I/O
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Precision Shunt Regulators with Reset in SOT23-3 MAX6330/MAX6331
Package Information
SOTPO3L.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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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