19-3981; Rev 0; 1/06 Speed-Switching Clock Generator with Power Fail The MAX7391 replaces ceramic resonators, crystals, and supervisory functions for microcontrollers in 3.3V and 5V applications. The MAX7391 provides a clock source, reset, and power-fail functions. The programmable power-fail function provides early warning of power failure and is configurable to detect either an external voltage or the VCC supply to the device. The clock output can be switched between normal and half-speed operation. This functionality allows the microcontroller to operate at reduced power and may be used to extend the time available to perform housekeeping tasks, such as writing data to flash during a power failure. Connecting the power-fail output to the SPEED input reduces clock speed automatically during power-fail events. The MAX7391 clock output is factory programmed to a frequency in the 1MHz to 16MHz range. Four standard frequencies are available. Other frequencies are available upon request. The maximum operating supply current is 5.5mA (typ) with a clock frequency of 12MHz. Unlike typical crystal and ceramic resonator oscillator circuits, the MAX7391 is resistant to EMI and vibration, and operates reliably at high temperatures. The highoutput drive current and absence of high-impedance nodes make the oscillator invulnerable to dirty or humid operating conditions. The MAX7391 is available in an 8-pin µMAX® package. The MAX7391 standard operating temperature range is from -40°C to +125°C. Applications White Goods Features ♦ Robust Microcontroller Clock and Supervisory Functions in a Single Package ♦ Integrated Reset and Power-Fail Functions ♦ Speed Select ♦ +2.7V to +5.5V Operation ♦ Factory-Trimmed Oscillator ♦ Reset Valid Down to 1.1V Supply Voltage ♦ ±10mA Clock-Output Drive Current ♦ ±4% Total Accuracy for -40°C to +125°C ♦ ±2.75% Total Accurac for 0°C to +85°C ♦ 5.5mA Operating Current (12MHz Version) ♦ -40°C to +125°C Temperature Range ♦ Surface-Mount Package ♦ 1MHz to 16MHz Factory Preset Frequency Range Ordering Information PART TEMP RANGE MAX7391srff -40°C to +125°C PIN-PACKAGE 8 µMAX PKG CODE U8-1 Note: “s” is a placeholder for the reset output type. Insert the symbol found in Table 2 in the place of “s.” “r” is a placeholder for the power-on reset (POR) voltage. Insert the symbol found in Table 1 in the place of “r.” “ff” is a placeholder for the nominal output frequency. Insert the symbol found in Table 3 in the place of “ff.” For example, MAX7391CMTP describes a device with 4.38V reset level, open-collector RST output, and a clock output frequency of 8MHz. Automotive Appliances and Controls Pin Configuration Handheld Products Portable Equipment TOP VIEW Microcontroller Systems PFI 1 VCC 2 Typical Application Circuit, Functional Diagram, and Selector Guide appear at end of data sheet. 8 CLOCK 7 RST/RST MAX7391 N.C. 3 6 SPEED GND 4 5 PFO µMAX is a registered trademark of Maxim Integrated Products, Inc. µMAX ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX7391 General Description MAX7391 Speed-Switching Clock Generator with Power Fail ABSOLUTE MAXIMUM RATINGS VCC to GND ...........................................................-0.3V to +6.0V All Other Pins to GND ................................-0.3V to (VCC + 0.3V) CLOCK, RST/RST, PFO Output Current ..........................±50mA Continuous Power Dissipation 8-Pin µMAX (derate 4.5mW/°C over TA = +70°C)........362mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+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 (Typical Application Circuit, VCC = +2.7V to +5.5V, TA = -40°C to +125°C, 1MHz to 16MHz output frequency range, typical values at VCC = +5.0V, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.5 V Minimum supply voltage for valid RST/RST output, TA = 0°C to +85°C 1.1 V fCLOCK = 12MHz 5.5 fCLOCK = 8MHz 4.5 Input is high 0.5 POWER REQUIREMENTS Operating Supply Voltage Valid RST/RST Supply Voltage VCC VCCR Operating Supply Current ICC 2.7 mA LOGIC INPUT: SPEED Input Leakage Current ILEAK Logic-Input High Voltage VIH Logic-Input Low Voltage VIL 0.7 x VCC µA V 0.3 x VCC V PUSH-PULL LOGIC OUTPUTS: RST/RST Output High VOH ISOURCE = 1mA Output Low VOL ISINK = 3mA VCC - 1.5 0.05 0.4 V V VOLO ISINK = 3mA 0.05 0.4 V VOHC ISOURCE = 5mA VOLC ISINK = 5mA OPEN-DRAIN LOGIC OUTPUTS: RST, PFO Output Low OUTPUT: CLOCK CLOCK Output High Voltage CLOCK Output Low Voltage CLOCK Accuracy 2 fCLOCK Table 3, VCC = +5.0V VCC - 0.3 -4 _______________________________________________________________________________________ V 0.3 V +4 % Speed-Switching Clock Generator with Power Fail (Typical Application Circuit, VCC = +2.7V to +5.5V, TA = -40°C to +125°C, 1MHz to 16MHz output frequency range, typical values at VCC = +5.0V, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER TYP MAX UNITS VCC = +5.0V (Note 2) 140 400 ppm/°C Clock Frequency Supply Voltage Coefficient TA = +25°C (Note 2) 0.67 1 %/V CLOCK Duty Cycle (Note 2) 50 55 % CLOCK Output Jitter Observation for 20s using a 500MHz oscilloscope 310 Clock Frequency Temperature Coefficient SYMBOL CONDITIONS MIN 45 ps RMS Output Rise Time tR CLOAD = 10pF, 10% to 90% of full scale (Note 2) 2.5 7.0 ns Output Fall Time tF CLOAD = 10pF, 90% to 10% of full scale (Note 2) 2.5 7.5 ns INTERNAL POWER-ON RESET VTH+ VCC rising, Table 1 Reset Voltage TA = +25°C VTH - 1.5% VTH + 1.5% TA = -40°C to +125°C VTH - 2.5% VTH + 2.5% V 250 µs 0.85 x VCC V 0.98 x VTH+ VTH- VCC falling tRST Figure 1 86 Power-Fail Select Threshold VSEL PFI input 0.65 x VCC VCC Monitoring Threshold (Internal Threshold) VITH VCC rising 4.06 4.38 4.60 V VIHYST VCC falling 1.0 2 4.0 %VITH VETH PFI rising 0.9 1.1 1.4 V VEHYST PFI falling 1.0 3.5 8.0 %VETH Reset Timeout Period 135 POWER FAIL Internal Threshold Hysteresis PFI Monitoring Threshold (External Threshold) External Threshold Hysteresis Note 1: All parameters are tested at TA = +25°C. Specifications over temperature are guaranteed by design. Note 2: Guaranteed by design. Not production tested. _______________________________________________________________________________________ 3 MAX7391 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (Typical Application Circuit, VCC = +5V, fCLOCK = 16MHz, TA = +25°C, unless otherwise noted.) FREQUENCY vs. TEMPERATURE 1.000 0.990 51 DUTY CYCLE (%) 1.010 1.020 1.010 1.000 0.980 49 4.20 5.50 4.85 VTH+ = 2.9V NORMALIZED TO TA = +25°C 0.980 3.55 50 0.990 NORMALIZED TO VCC = 5V VTH+ = 2.9V 2.90 DUTY CYCLE vs. SUPPLY VOLTAGE 52 MAX7391 toc02 MAX7391 toc01 1.030 NORMALIZED FREQUENCY NORMALIZED FREQUENCY 1.040 MAX7391 toc03 FREQUENCY vs. SUPPLY VOLTAGE 1.020 48 -40 -25 -10 5 20 35 50 65 80 95 110 125 2.90 3.55 4.20 5.50 4.85 VCC (V) TEMPERATURE (°C) VCC (V) DUTY CYCLE vs. TEMPERATURE CLOCK OUTPUT WAVEFORM WITH CL = 10pF CLOCK OUTPUT WAVEFORM WITH CL = 50pF MAX7391 toc05 MAX7391 toc04 52 MAX7391 toc06 VCC = 3.3V VCC = 3.3V 51 DUTY CYCLE (%) 50 CLOCK 1V/div CLOCK 1V/div 49 48 -40 -25 -10 5 20 35 50 65 80 95 110 125 40ns/div 40ns/div TEMPERATURE (°C) SUPPLY CURRENT vs. TEMPERATURE 4 CLOCK 1V/div SUPPLY CURRENT vs. SUPPLY VOLTAGE 5 MAX7391 toc08 5 VCC = 5V 4 3 VCC = 3.3V ICC (mA) MAX7391 toc07 MAX7391 toc09 CLOCK OUTPUT WAVEFORM WITH CL = 100pF ICC (mA) MAX7391 Speed-Switching Clock Generator with Power Fail 3 2 2 1 1 VTH+ = 2.9V 40ns/div -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4 2.90 3.55 4.20 VCC (V) _______________________________________________________________________________________ 4.85 5.50 Speed-Switching Clock Generator with Power Fail MAXIMUM VCC TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE POWER-ON RESET BEHAVIOR MAX7391 toc11 VCC 2V/div 1000 VCC 5V/div CLOCK 5V/div CLOCK 2V/div RST 5V/div PFO 5V/div 1µs/div TRANSIENT DURATION (µs) MAX7391 toc10 MAX7391 toc12 CLOCK SETTLING TIME FROM START RESET OCCURS ABOVE THIS CURVE 100 10 VCC FALLING FROM VTH+ + 100mV 1 20µs/div 100 200 300 400 500 600 700 800 900 1000 RESET THRESHOLD OVERDRIVE (mV) CLOCK RESPONSE TO SPEED SELECT INPUT RISING THRESHOLD vs. TEMPERATURE MAX7391 toc13 SPEED 2V/div MAX7391 toc14 2.90 VTH+ (V) 2.88 2.86 2.84 CLOCK 2V/div 2.82 2.80 200ns/div -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX7391 Typical Operating Characteristics (continued) (Typical Application Circuit, VCC = +5V, fCLOCK = 16MHz, TA = +25°C, unless otherwise noted.) Speed-Switching Clock Generator with Power Fail MAX7391 Pin Description PIN NAME FUNCTION 1 PFI Power-Fail Input. PFI monitors the condition of either an external supplied voltage or VCC. See the Power Fail section for more details. 2 VCC Power Input. Connect VCC to the power supply. Bypass VCC to GND with a 0.1µF capacitor. Install the bypass capacitor as close to the device as possible. 3 N.C. No Connection 4 GND Ground 5 PFO Power-Fail Output. Open-drain output asserts when the voltage being monitored drops below the power-fail threshold voltage. 6 SPEED Clock-Speed Select Input. Connect SPEED high for the factory-trimmed clock output frequency. Connect SPEED low to reduce the clock output frequency by half. 7 RST/RST Reset Output. Reset output is available in one of three configurations: push-pull RST, push-pull RST, or open-drain RST. The reset output occurs if any combination of the following conditions occurs: reset output is asserted during power-up, and whenever VCC is below the reset threshold level; for devices with WDI, reset output asserts when WDI does not receive a rising or falling edge within the watchdog timeout period. 8 CLOCK Clock Output Detailed Description The MAX7391 replaces ceramic resonators, crystals, and supervisory functions for microcontrollers in 3.3V and 5V applications. The MAX7391 provides a clock source, reset, and power-fail functions. The power-fail output provides early warning of power failure. The power-fail threshold is configurable to detect either an external voltage or the VCC supply voltage to the device. The clock output can be switched between normal and half-speed operation. This functionality allows the microcontroller to operate at reduced power and may be used to extend the time available to perform housekeeping tasks, such as writing data to flash, during a power failure. Connecting the power-fail output (PFO) to the SPEED input reduces clock speed automatically during power-fail events. The integrated reset provides the power-supply monitoring functions necessary to ensure correct microcontroller operation. The reset circuit has built-in power-supply transient immunity and provides both power-on reset and power-fail or brownout reset functionality. Two standard factory-trimmed reset levels are available. A power-fail function is provided for power-supply voltage monitoring and can provide advance notice of an impending power failure. The power-fail input monitors external power-supply voltages through an external resistive divider. Connect PFI to VCC to monitor VCC. 6 Clock Output (CLOCK) The push-pull clock output (CLOCK) drives a groundconnected 1kΩ load or a positive supply connected 500Ω load to within 300mV of either supply rail. CLOCK remains stable over the full operating voltage range and does not generate short output cycles during either power-on or power-off. A typical startup characteristic is shown in the Typical Operating Characteristics section. The clock output frequency is reduced by a factor of two by taking SPEED low. This functionality allows the microcontroller to operate at reduced power and may be used to extend the time available to perform housekeeping tasks, such as writing data to flash during power failure. Reset The reset function drives the microcontroller reset input to prevent operation in the cases of the initial power-on setting, low power-supply voltages, and the failed watchdog operations. Three reset output versions are available: push-pull RST, push-pull RST, and open-drain RST. The reset timeout period (tRST) is nominally 135s. Power-On Reset (POR) The internal power-on reset (POR) circuit detects the power-supply voltage (VCC) level at startup. The POR circuit starts the oscillator when VCC exceeds the reset rising threshold level (VTH+). The reset output remains asserted from the time VCC crosses the VTH+ and continues to be asserted for the reset timeout period (tRST). Upon completion of the reset timeout, the reset output is released. See Figure 1. _______________________________________________________________________________________ Speed-Switching Clock Generator with Power Fail Figure 1 shows the reset output (RST/RST) behavior during power-up and brownout. Power Fail The power-fail function provides early warning of a power failure. The power-fail comparator detects the condition of either an external voltage or the VCC supply voltage. Internal (VCC) detection is configured by connecting PFI to VCC. The internal VCC rising threshold (VITH) is set at 4.38V. The open-drain PFO asserts low if the VCC supply voltage drops below the VCC falling threshold value (VIHYST). The VCC falling threshold is nominally 2% below the VCC rising threshold. External power-fail detection is selected when the applied voltage on PFI (VPFI) is less than 0.65 x VCC (VSEL minimum). When the voltage on PFI is more than 0.85 x VCC (VSEL maximum), the device switches to internal monitoring. External power-fail detection is normally used with a resistive divider from the supply being monitored. See the Typical Application Circuit. For a 3.3V supply, the voltage on PFI needs to be set externally and less than 0.65 x VCC (VSEL minimum). To set the voltage on PFI externally, choose R1 and R2 so that: VPFI = R2 × PowerSupply R2 + R1 See Figure 1 for PFO behavior during power-up and brownout. 5 VITH VCC (V) 4 VITH - VIHYST VTH+ 3 VTH- 2 1 VCCR CLK tRST RST PFO CLOCK STARTS ON INTERNAL POR (VTH+, VCC RISING). RST RELEASES AFTER THE RESET TIMEOUT PERIOD. PFO ASSERTS AS VCC DROPS BELOW VTH. CLOCK FREQUENCY REDUCTION SHOWN IS ACHIEVED BY CONNECTING SPEED TO PFO. RST ASSERTS ON RESET FALLING VOLTAGE (VTH-, VCC FALLING). CLOCK STOPS. RST CONTINUES TO ASSERT UNTIL VCCR. Figure 1. RST/RST and PFO Behavior During Power-Up and Brownout _______________________________________________________________________________________ 7 MAX7391 Low-Voltage Lockout The reset output asserts whenever VCC drops below the reset falling threshold, VTH-. The difference between the reset rising and falling threshold values is VTH+ - (VTH-). The nominal hysteresis value is 2% of the reset rising threshold value. The reset detection circuitry provides filtering to prevent triggering on negative voltage spikes. See the Typical Operating Characteristics for a plot of maximum transient duration without causing a reset pulse vs. reset comparator overdrive. Speed-Switching Clock Generator with Power Fail MAX7391 Selector Guide PART FREQUENCY RANGE (MHz) RESET FUNCTION WATCHDOG INPUT (WDI) / WATCHDOG OUTPUT (WDO) POWER-FAIL INPUT (PFI)/POWER-FAIL OUTPUT (PFO) SPEED PINPACKAGE MAX7387 1 to 32 Yes Yes/yes Yes/yes — 10 µMAX MAX7388 1 to 32 Yes Yes/no No/yes — 8 µMAX MAX7389 1 to 32 Yes Yes/yes — — 8 µMAX MAX7390 1 to 32 Yes Yes/no — Yes 8 µMAX MAX7391 1 to 32 Yes — Yes/yes Yes 8 µMAX Note: Other versions with different features are available. Refer to the MAX7387/MAX7388 and MAX7389/MAX7390 data sheets. Applications Information Interfacing to a Microcontroller Clock Input The clock output is a push-pull, CMOS logic output, which directly drives any microprocessor (µP) or microcontroller (µC) clock input. There are no impedancematching issues when using the MAX7391. Operate the MAX7391 and µC (or other clock input device) from the same supply voltage level. Refer to the microcontroller data sheet for clock-input compatibility with external clock signals. Table 3 lists clock output frequency. The MAX7391 requires no biasing components or load capacitance. When using the MAX7391 to retrofit a crystal oscillator, remove all biasing components from the oscillator input. Table 1. POR Voltage POWER-ON RESET VOLTAGE (VTH) r 4.38 M 3.96 J 3.44 N 3.34 P 3.13 Q 2.89 S 2.82 V 2.5 X Note: Standard values are shown in bold. Contact factory for other POR voltages. Table 2. Reset Output Type OUTPUT TYPE s Push-pull RST A Push-pull RST B Open collector RST C Power-Supply Considerations The MAX7391 operates with power-supply voltages in the 2.7V to 5.5V range. Good power-supply decoupling is needed to maintain the power-supply rejection performance of the MAX7391. Bypass VCC to GND with a 0.1µF surface-mount ceramic capacitor. Mount the bypass capacitor as close to the device as possible. If possible, mount the MAX7391 close to the microcontroller’s decoupling capacitor so that additional decoupling is not required. A larger-value bypass capacitor is recommended if the MAX7391 is to operate with a large capacitive load. Use a bypass capacitor value of at least 1000 times that of the output load capacitance. Output Jitter The MAX7391’s jitter performance is given in the Electrical Characteristics table as a peak-to-peak value obtained by observing the output of the device for 20s with a 500MHz oscilloscope. Jitter measurements are approximately proportional to the period of the output frequency of the device. Thus, a 4MHz part has approximately twice the jitter value of an 8MHz part. The jitter performance of all clock sources degrades in the presence of mechanical and electrical interference. The MAX7391 is immune to vibration, shock, and EMI influences, and thus provides a considerably more robust clock source than crystal- or ceramic-resonatorbased oscillator circuits. Table 3. Clock Output Frequency CLOCK FREQUENCY (fCLOCK) (MHz) ff 4 RD 8 TP 12 VB 16 WB Note: Contact factory for other frequencies. Note: Standard values are shown in bold. Contact factory for other output types. 8 _______________________________________________________________________________________ Speed-Switching Clock Generator with Power Fail MAX7391 RST/RST PRESCALER POWER-ON RESET RESET TIMER OSCILLATOR CLOCK SPEED PFI PFO INTERNAL (VCC DETECTION) N V_TH GND Typical Application Circuit POWER SUPPLY DC-DC 5V VCC R1 RST/RST PFO RST/RST INT MAX7391 PFI µC SPEED R2 CLOCK OSC1 GND Chip Information PROCESS: BiCMOS _______________________________________________________________________________________ 9 MAX7391 Functional Diagram Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 4X S 8 E Ø0.50±0.1 8 INCHES DIM A A1 A2 b H c D e E H 0.6±0.1 1 L 1 α 0.6±0.1 S BOTTOM VIEW D MIN 0.002 0.030 MAX 0.043 0.006 0.037 0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6° 0° 0.0207 BSC 8LUMAXD.EPS MAX7391 Speed-Switching Clock Generator with Power Fail MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95 0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0° 6° 0.5250 BSC TOP VIEW A1 A2 e A α c b L SIDE VIEW FRONT VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 8L uMAX/uSOP APPROVAL DOCUMENT CONTROL NO. 21-0036 REV. J 1 1 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. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2006 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.