View MAX6316_200700.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-0496; Rev 3; 1/99
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
________________General Description
The MAX6316-MAX6322 family of microprocessor (P) supervisory circuits monitors power supplies and microprocessor activity in digital systems. It offers several combinations of push/pull, open-drain, and bidirectional (such as Motorola 68HC11) reset outputs, along with watchdog and manual-reset features. The Selector Guide below lists the specific functions available from each device. These devices are specifically designed to ignore fast negative transients on VCC. Resets are guaranteed valid for VCC down to 1V. These devices are available in 26 factory-trimmed reset threshold voltages (from 2.5V to 5V, in 100mV increments), featuring four minimum power-on reset timeout periods (from 1ms to 1.12sec), and four watchdog timeout periods (from 6.3ms to 25.6sec). Nine standard versions are available with an order increment requirement of 2500 pieces (see Standard Versions table); contact the factory for availability of other versions, which have an order increment requirement of 10,000 pieces. The MAX6316-MAX6322 are offered in a miniature 5-pin SOT23 package.
____________________________Features
o Small 5-Pin SOT23 Package o Available in 26 Reset Threshold Voltages 2.5V to 5V, in 100mV Increments o Four Reset Timeout Periods 1ms, 20ms, 140ms, or 1.12sec (min) o Four Watchdog Timeout Periods 6.3ms, 102ms, 1.6sec, or 25.6sec (typ) o Four Reset Output Stages Active-High, Push/Pull Active-Low, Push/Pull Active-Low, Open-Drain Active-Low, Bidirectional o Guaranteed Reset Valid to VCC = 1V o Immune to Short Negative VCC Transients o Low Cost o No External Components
MAX6316-MAX6322
_______________Ordering Information
PART MAX6316LUK____-T MAX6316MUK____-T MAX6317HUK____-T MAX6318HUK____-T MAX6318MHUK____-T TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 5 SOT23-5 5 SOT23-5 5 SOT23-5 5 SOT23-5 5 SOT23-5
________________________Applications
Portable Computers Computers Controllers Intelligent Instruments Portable/Battery-Powered Equipment Embedded Control Systems
Ordering Information continued at end of data sheet. Typical Operating Circuit and Pin Configurations appear at end of data sheet.
___________________________________________________________________Selector Guide
PART MAX6316L MAX6316M MAX6317H MAX6318LH MAX6318MH** MAX6319LH MAX6319MH** MAX6320P MAX6321HP MAX6322HP -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- WATCHDOG INPUT MANUAL RESET INPUT RESET OUTPUTS* ACTIVE-LOW PUSH/PULL ACTIVE-HIGH PUSH/PULL -- -- -- -- ACTIVE-LOW BIDIRECTIONAL -- ACTIVE-LOW OPEN-DRAIN -- -- -- -- -- -- --
* The MAX6318/MAX6319/MAX6321/MAX6322 feature two types of reset output on each device. **Future product--contact factory for availability.
________________________________________________________________ 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 1-800-835-8769.
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
ABSOLUTE MAXIMUM RATINGS
Voltage (with respect to GND) VCC......................................................................-0.3V to +6V RESET (MAX6320/MAX6321/MAX6322 only)...... -0.3V to +6V All Other Pins.........................................-0.3V to (VCC + 0.3V) Input/Output Current, All Pins .............................................20mA Continuous Power Dissipation (TA = +70C) SOT23-5 (derate 7.1mW/C above +70C)...............571mW Operating Temperature Range............................-40C to +85C Junction Temperature ......................................................+150C 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
(VCC = 2.5V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Operating Voltage Range SYMBOL VCC CONDITIONS TA = -40C to +85C MAX6316/MAX6317/MAX6318/ MAX6320/MAX6321: MR and WDI unconnected MAX6319/MAX6322: MR unconnected Reset Threshold Temperature Coefficient Reset Threshold (Note 2) Reset Threshold Hysteresis MAX63_ _A_-T Reset Active Timeout Period tRP MAX63_ _B_-T MAX63_ _C_-T MAX63_ _D_-T VCC to RESET Delay tRD VCC falling at 1mV/s VCC 1.0V, ISINK = 50A VOL RESET Output Voltage VOH VOL RESET Output Voltage VOH VCC 1.2V, ISINK = 100A VCC 2.7V, ISINK = 1.2mA VCC 4.5V, ISINK = 3.2mA VCC 2.7V, ISOURCE = 500A VCC 4.5V, ISOURCE = 800A VCC 2.7V, ISINK = 1.2mA VCC 4.5V, ISINK = 3.2mA VCC 1.8V, ISOURCE = 150A VCC 2.7V, ISOURCE = 500A VCC 4.5V, ISOURCE = 800A 0.8 x VCC 0.8 x VCC VCC - 1.5 0.8 x VCC VCC - 1.5 0.3 0.4 V 1 20 140 1120 VTH/C VRST TA = +25C TA = -40C to +85C VCC = 5.5V VCC = 3.6V VCC = 5.5V VCC = 3.6V MIN 1 10 5 5 3 40 VTH -1.5% VTH VTH +1.5% VTH -2.5% VTH VTH +2.5% 3 1.4 28 200 1600 40 0.3 0.3 0.3 0.4 V 2 40 280 2240 s ms TYP MAX 5.5 20 12 12 8 ppm/C V mV A UNITS V
Supply Current
ICC
PUSH/PULL RESET OUTPUT (MAX6316L/MAX6317H/MAX6318_H/MAX6319_H/MAX6321HP/MAX6322HP)
Note 1: Over-temperature limits are guaranteed by design, not production tested. Note 2: A factory-trimmed voltage divider programs the nominal reset threshold (VTH). Factory-trimmed reset thresholds are available in 100mV increments from 2.5V to 5V (see Table 1 at end of data sheet).
2
_______________________________________________________________________________________
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 2.5V to 5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP 400 333 333 666 666 0.4 4.2 0.65 20 4.7 5.2 0.3 0.3 0.3 0.4 1.0 A V V mA k ns MAX UNITS ns BIDIRECTIONAL RESET OUTPUT (MAX6316M/MAX6318MH/MAX6319MH) Transition Flip-Flop Setup Time tS (Note 3) VCC = 3.0V, CL = 120pF RESET Output Rise Time (Note 4) Active Pull-Up Enable Threshold RESET Active Pull-Up Current RESET Pull-Up Resistance OPEN-DRAIN RESET OUTPUT (MAX6320P/MAX6321HP/MAX6322HP) VCC 1.0V, ISINK = 50A RESET Output Voltage VOL VCC 1.2V, ISINK = 100A VCC 2.7V, ISINK = 1.2mA VCC 4.5V, ISINK = 3.2mA Open-Drain Reset Output Leakage Current ILKG tR VCC = 5.0V, CL = 200pF VCC = 3.0V, CL = 250pF VCC = 5.0V, CL = 400pF VPTH VCC = 5.0V VCC = 5.0V
MAX6316-MAX6322
WATCHDOG INPUT (MAX6316/MAX6317H/MAX6318_H/MAX6320P/MAX6321HP) MAX63_ _ _ W-T Watchdog Timeout Period tWD MAX63_ _ _ X-T MAX63_ _ _ Y-T MAX63_ _ _ Z-T WDI Pulse Width WDI Input Threshold WDI Input Current (Note 6) tWDI VIL VIH IWDI VIL = 0.3 x VCC, VIH = 0.7 x VCC (Note 5) WDI = VCC, time average VWDI = 0, time average -20 0.8 2.0 0.3 x VCC 0.7 x VCC 1 100 35 VCC = 5V 52 230 75 s ns k ns V 4.3 71 1.12 17.9 50 0.3 x VCC 0.7 x VCC 120 -15 160 6.3 102 1.6 25.6 9.3 153 2.4 38.4 ms sec ns V A
MANUAL-RESET INPUT (MAX6316_/MAX6317H/MAX6319_H/MAX6320P/MAX6322HP) VIL MR Input Threshold VIH VIL VIH MR Input Pulse Width MR Glitch Rejection MR Pull-Up Resistance MR to Reset Delay Note 3: Note 4: Note 5: Note 6: VTH > 4.0V VTH < 4.0V
This is the minimum time RESET must be held low by an external pull-down source to set the active pull-up flip-flop. Measured from RESET VOL to (0.8 x VCC), RLOAD = . WDI is internally serviced within the watchdog period if WDI is left unconnected. The WDI input current is specified as the average input current when the WDI input is driven high or low. The WDI input is designed for a three-stated-output device with a 10A maximum leakage current and capable of driving a maximum capacitive load of 200pF. The three-state device must be able to source and sink at least 200A when active.
_______________________________________________________________________________________
3
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
__________________________________________Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
MAX6316/17/19/20/22 MANUAL-RESET TO RESET PROPAGATION DELAY vs. TEMPERATURE
MAX6316toc03
MAX6316/17/18/20/21 SUPPLY CURRENT vs. TEMPERATURE
MAX6316toc01
VCC FALLING TO RESET PROPAGATION DELAY vs. TEMPERATURE
100 90 RESET PROPAGATION DELAY (s) 80 70 60 50 40 30 20 10 0 320 300 PROPAGATION DELAY (ns) 280 260 240 220 200 180 160 140 -40 -20 0 20 40 60 80 100 VCC FALLING AT 1mV/s VRST - VCC = 100mV
9 8 SUPPLY CURRENT (A) 7 6 5 4 3 2 1 0 -40 -20 0 20 40 60 80 VCC = 1V VCC = 3V VCC = 5V
VCC = 5V
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
NORMALIZED RESET TIMEOUT PERIOD vs. TEMPERATURE
MAX6316toc05
MAX6316/17/18/20/21 NORMALIZED WATCHDOG TIMEOUT PERIOD vs. TEMPERATURE
NORMALIZED WATCHDOG TIMEOUT PERIOD 1.04 1.03 1.02 1.01 1.00 0.99 0.98 0.97 0.96 0.95 -40 -20 0 20 40 60 80 100
MAX6316toc06
1.05 NORMALIZED RESET TIMEOUT PERIOD 1.04 1.03 1.02 1.01 1.00 0.99 0.98 0.97 0.96 0.95 -40 -20 0 20 40 60 80
1.05
100
TEMPERATURE (C)
TEMPERATURE (C)
MAXIMUM VCC TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE
MAX6316toc08
MAX6316M/6318MH/6319MH BIDIRECTIONAL PULL-UP CHARACTERISTICS
MAX6316toc09
80 RESET OCCURS ABOVE LINES 70 TRANSIENT DURATION (s) VRST = 3.3V 60 50 40 30 20 10 0 10 100 VRST = 4.63V
+5V 74HC05 INPUT 4.7k 100pF
PASSIVE 4.7k PULL-UP 2V/div RESET, ACTIVE PULL-UP 2V/div
+5V
VRST = 2.63V
INPUT
74HC05 100pF
VCC RESET MR GND
RESET INPUT 5V/div
1000
200ns/div
RESET THRESHOLD OVERDRIVE (mV) VRST - VCC
4
_______________________________________________________________________________________
MAX6316toc04
10
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
______________________________________________________________Pin Description
PIN MAX6316L MAX6316M MAX6320P MAX6318LH MAX6318MH MAX6321HP MAX6319LH MAX6319MH MAX6322HP NAME FUNCTION
MAX6316-MAX6322
MAX6317H
MAX6316L/MAX6318LH/MAX6319LH: Active-Low, Reset Output. CMOS push/pull output (sources and sinks current). MAX6316M/MAX6318MH/MAX6319MH: Bidirectional, Active-Low, Reset Output. Intended to interface directly to microprocessors with bidirectional resets such as the Motorola 68HC11. MAX6320P/MAX6321HP/MAX6322HP: Open-Drain, Active-Low, Reset Output. NMOS output (sinks current only). Connect a pull-up resistor from RESET to any supply voltage up to 6V. -- 2 1 2 3 2 3 2 RESET GND Active-High, Reset Output. CMOS push/pull output (sources and sinks current). Inverse of RESET. Ground Active-Low, Manual Reset Input. Pull low to force a reset. Reset remains asserted for the duration of the Reset Timeout Period after MR transitions from low to high. Leave unconnected or connected to VCC if not used. Watchdog Input. Triggers a reset if it remains either high or low for the duration of the watchdog timeout period. The internal watchdog timer clears whenever a reset asserts or whenever WDI sees a rising or falling edge. To disable the watchdog feature, leave WDI unconnected or three-state the driver connected to WDI. Supply Voltage. Reset is asserted when VCC drops below the Reset Threshold Voltage (VRST). Reset remains asserted until VCC rises above VRST and for the duration of the Reset Timeout Period (tRP) once VCC rises above VRST.
1
--
1
1
RESET
3
3
--
4
MR
4
4
4
--
WDI
5
5
5
5
VCC
_______________________________________________________________________________________
5
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
VCC
MAX6316-MAX6322
RESET (ALL EXCEPT MAX6317) RESET (ALL EXCEPT MAX6316/MAX6320P)
RESET GENERATOR VCC 1.23V 52k
MR (ALL EXCEPT MAX6318/MAX6321) WDI (ALL EXCEPT MAX6319/MAX6322) 52k WATCHDOG TRANSITION DETECTOR WATCHDOG TIMER
GND
Figure 1. Functional Diagram
_______________Detailed Description
A microprocessor's (P) reset input starts or restarts the P in a known state. The reset output of the MAX6316- MAX6322 P supervisory circuits interfaces with the reset input of the P, preventing code-execution errors during power-up, power-down, and brownout conditions (see the Typical Operating Circuit). The MAX6316/ MAX6317/MAX6318/MAX6320/MAX6321 are also capable of asserting a reset should the P become stuck in an infinite loop.
the watchdog timeout period (tWD). Reset remains asserted for the specified reset active timeout period (tRP) after VCC rises above the reset threshold, after MR transitions low to high, or after the watchdog timer asserts the reset (MAX6316_/MAX6317H/MAX6318_H/MAX6320P/ MAX6321HP). After the reset active timeout period (tRP) expires, the reset output deasserts, and the watchdog timer restarts from zero (Figure 2).
VCC 1V GND RESET tRP tRD VRST VRST 1V
Reset Output
The MAX6316L/MAX6318LH/MAX6319LH feature an active-low reset output, while the MAX6317H/ MAX6318_H/MAX6319_H/MAX6321HP/MAX6322HP feature an active-high reset output. RESET is guaranteed to be a logic low and RESET is guaranteed to be a logic high for VCC down to 1V. The MAX6316-MAX6322 assert reset when VCC is below the reset threshold (V RST ), when MR is pulled low (MAX6316_/MAX6317H/MAX6319_H/MAX6320P/ MAX6322HP only), or if the WDI pin is not serviced within
6
RESET GND
tRP
tRD
Figure 2. Reset Timing Diagram
_______________________________________________________________________________________
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
Bidirectional RESET Output
The MAX6316M/MAX6318MH/MAX6319MH are designed to interface with Ps that have bidirectional reset pins, such as the Motorola 68HC11. Like an open-drain output, these devices allow the P or other devices to pull the bidirectional reset (RESET) low and assert a reset condition. However, unlike a standard open-drain output, it includes the commonly specified 4.7k pull-up resistor with a P-channel active pull-up in parallel. This configuration allows the MAX6316M/MAX6318MH/ MAX6319MH to solve a problem associated with Ps that have bidirectional reset pins in systems where several devices connect to RESET (Figure 3). These Ps can often determine if a reset was asserted by an external device (i.e., the supervisor IC) or by the P itself (due to a watchdog fault, clock error, or other source), and then jump to a vector appropriate for the source of the reset. However, if the P does assert reset, it does not retain the information, but must determine the cause after the reset has occurred. The following procedure describes how this is done in the Motorola 68HC11. In all cases of reset, the P pulls RESET low for about four external-clock cycles. It then releases RESET, waits for two external-clock cycles, then checks RESET's state. If RESET is still low, the P concludes that the source of the reset was external and, when RESET eventually reaches the high state, it jumps to the normal reset vector. In this case, storedstate information is erased and processing begins from
VCC VCC
scratch. If, on the other hand, RESET is high after a delay of two external-clock cycles, the processor knows that it caused the reset itself and can jump to a different vector and use stored-state information to determine what caused the reset. A problem occurs with faster Ps; two external-clock cycles are only 500ns at 4MHz. When there are several devices on the reset line, and only a passive pull-up resistor is used, the input capacitance and stray capacitance can prevent RESET from reaching the logic high state (0.8 x VCC) in the time allowed. If this happens, all resets will be interpreted as external. The P output stage is guaranteed to sink 1.6mA, so the rise time can not be reduced considerably by decreasing the 4.7k internal pull-up resistance. See Bidirectional Pull-Up Characteristics in the Typical Operating Characteristics. The MAX6316M/MAX6318MH/MAX6319MH overcome this problem with an active pull-up FET in parallel with the 4.7k resistor (Figures 4 and 5). The pull-up transistor holds RESET high until the P reset I/O or the supervisory circuit itself forces the line low. Once RESET goes below VPTH, a comparator sets the transition edge flip-flop, indicating that the next transition for RESET will be low to high. When RESET is released, the 4.7k resistor pulls RESET up toward VCC. Once RESET rises above VPTH but is below (0.85 x VCC), the active P-channel pull-up turns on. Once RESET rises above (0.85 x VCC) or the 2s one-shot times out, the active pull-up turns off. The parallel combination of the 4.7k pull-up and the
MAX6316-MAX6322
WDI* MR** RESET*** RESET CIRCUITRY
4.7k RESET RESET
68HC11
RESET CIRCUITRY CIN
CIN
CSTRAY
MAX6316M MAX6318MH MAX6319MH
* MAX6316M/MAX6318MH ** MAX6316M/MAX6319MH *** ACTIVE-HIGH PUSH/PULL MAX6318MH/MAX6319MH
RESET CIN OTHER DEVICES
Figure 3. MAX6316M/MAX6318MH/MAX6319MH Supports Additional Devices on the Reset Bus
_______________________________________________________________________________________ 7
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
VCC
LASERTRIMMED RESISTORS
MAX6316M MAX6318MH MAX6319MH
VCC VREF 52k
RESET GENERATOR WATCHDOG ON 2s ONE SHOT CIRCUITRY VCC 2s ONE SHOT TRANSITION FLIP-FLOP R FF S Q 4.7k
MR
(MAX6316M/ MAX6319MH) (MAX6316M/ MAX6318MH)
WDI
RESET
ACTIVE PULL-UP ENABLE COMPARATOR
0.65V
0.85VCC
GND
Figure 4. MAX6316/MAX6318MH/MAX6319MH Bidirectional Reset Output Functional Diagram
8
_______________________________________________________________________________________
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
P-channel transistor on-resistance quickly charges stray capacitance on the reset line, allowing RESET to transition from low to high within the required two electronic-clock cycles, even with several devices on the reset line. This process occurs regardless of whether the reset was caused by VCC dipping below the reset threshold, the watchdog timing out, MR being asserted, or the P or other device asserting RESET. The parts do not require an external pull-up. To minimize supply current consumption, the internal 4.7k pull-up resistor disconnects from the supply whenever the MAX6316M/ MAX6318MH/MAX6319MH assert reset. register a logic low (see Electrical Characteristics), and small enough to register a logic high while supplying all input current and leakage paths connected to the RESET line. A 10k pull-up is sufficient in most applications.
MAX6316-MAX6322
Manual-Reset Input
The MAX6316_/MAX6317H/MAX6319_H/MAX6320P/ MAX6322HP feature a manual-reset input. A logic low on MR asserts a reset. After MR transitions low to high, reset remains asserted for the duration of the reset timeout period (tRP). The MR input is connected to VCC through an internal 52k pull-up resistor and therefore can be left unconnected when not in use. MR can be driven with TTL-logic levels in 5V systems, with CMOS-logic levels in 3V systems, or with open-drain or open-collector output devices. A normally-open momentary switch from MR to ground can also be used; it requires no external debouncing circuitry. MR is designed to reject fast, negative-going transients (typically 100ns pulses). A 0.1F capacitor from MR to ground provides additional noise immunity. The MR input pin is equipped with internal ESD-protection circuitry that may become forward biased. Should MR be driven by voltages higher than VCC, excessive current would be drawn, which would damage the part. For example, assume that MR is driven by a +5V supply other than VCC. If VCC drops lower than +4.7V, MR's absolute maximum rating is violated [-0.3V to (VCC + 0.3V)], and undesirable current flows through the ESD structure from MR to VCC. To avoid this, use the same supply for MR as the supply monitored by VCC. This guarantees that the voltage at MR will never exceed VCC.
Open-Drain RESET Output
The MAX6320P/MAX6321HP/MAX6322HP have an active-low, open-drain reset output. This output structure will sink current when RESET is asserted. Connect a pull-up resistor from RESET to any supply voltage up to 6V (Figure 6). Select a resistor value large enough to
VCC RESET 0.7V tS RESET PULLED LOW BY C OR RESET GENERATOR tRP OR C RESET DELAY tR 0.8 x VCC
ACTIVE PULL-UP TURNS ON
Figure 5. Bidirectional RESET Timing Diagram
Watchdog Input
The MAX6316_/MAX6317H/MAX6318_H/MAX6320P/ MAX6321HP feature a watchdog circuit that monitors the P's activity. If the P does not toggle the watchdog input (WDI) within the watchdog timeout period (tWD), reset asserts. The internal watchdog timer is cleared by reset or by a transition at WDI (which can detect pulses as short as 50ns). The watchdog timer remains cleared while reset is asserted. Once reset is released, the timer begins counting again (Figure 7). The WDI input is designed for a three-stated output device with a 10A maximum leakage current and the capability of driving a maximum capacitive load of 200pF. The three-state device must be able to source and sink at least 200A when active. Disable the watchdog function by leaving WDI unconnected or by three-stating the driver connected to WDI. When the watchdog timer is left open circuited, the timer is cleared internally at intervals equal to 7/8 of the watchdog period.
+3.3V
+5.0V
VCC MR* WDI** RESET*** RESET 5V SYSTEM 10k
MAX6320 MAX6321 MAX6322
GND
* MAX6320/MAX6322 ** MAX6320/MAX6321 *** MAX6321/MAX6322
Figure 6. MAX6320P/MAX6321HP/MAX6322HP Open-Drain RESET Output Allows Use with Multiple Supplies
_______________________________________________________________________________________
9
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
VCC tRST RESET tRP
tWD
tRP
MAX6316 MAX6318 MAX6319
VCC
VCC
WDI GND RESET 100k
MAX6316/MAX6317 MAX6318/MAX6320 MAX6321 Figure 7. Watchdog Timing Relationship Figure 8. Ensuring RESET Valid to VCC = 0 on Active-Low Push/Pull and Bidirectional Outputs
Applications Information
Watchdog Input Current
The WDI input is internally driven through a buffer and series resistor from the watchdog counter. For minimum watchdog input current (minimum overall power consumption), leave WDI low for the majority of the watchdog timeout period. When high, WDI can draw as much as 160A. Pulsing WDI high at a low duty cycle will reduce the effect of the large input current. When WDI is left unconnected, the watchdog timer is serviced within the watchdog timeout period by a low-high-low pulse from the counter chain.
MAX6317 MAX6318 MAX6319 MAX6321* MAX6322* VCC
GND RESET VCC
100k
Negative-Going VCC Transients
These supervisors are immune to short-duration, negative-going VCC transients (glitches), which usually do not require the entire system to shut down. Typically, 200ns large-amplitude pulses (from ground to VCC) on the supply will not cause a reset. Lower amplitude pulses result in greater immunity. Typically, a VCC transient that goes 100mV under the reset threshold and lasts less than 4s will not trigger a reset. An optional 0.1F bypass capacitor mounted close to VCC provides additional transient immunity.
*THIS SCHEMATIC DOES NOT WORK ON THE OPEN-DRAIN OUTPUTS OF THE MAX6321/MAX6322.
Figure 9. Ensuring RESET Valid to VCC = 0 on Active-High Push/Pull Outputs
source current. This scheme does not work with the open-drain outputs of the MAX6320/MAX6321/MAX6322. The resistor value used is not critical, but it must be large enough not to load the reset output when VCC is above the reset threshold. For most applications, 100k is adequate.
Ensuring Valid Reset Outputs Down to VCC = 0
The MAX6316_/MAX6317H/MAX6318_H/MAX6319_H/ MAX6321HP/MAX6322HP are guaranteed to operate properly down to VCC = 1V. In applications that require valid reset levels down to VCC = 0, a pull-down resistor to active-low outputs (push/pull and bidirectional only, Figure 8) and a pull-up resistor to active-high outputs (push/pull only, Figure 9) will ensure that the reset line is valid while the reset output can no longer sink or
10
Watchdog Software Considerations (MAX6316/MAX6317/MAX6318/ MAX6320/MAX6321)
One way to help the watchdog timer monitor software execution more closely is to set and reset the watchdog input at different points in the program, rather than pulsing the watchdog input high-low-high or low-highlow. This technique avoids a stuck loop, in which the watchdog timer would continue to be reset inside the loop, keeping the watchdog from timing out.
______________________________________________________________________________________
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
Figure 10 shows an example of a flow diagram where the I/O driving the watchdog input is set high at the beginning of the program, set low at the end of every subroutine or loop, then set high again when the program returns to the beginning. If the program should hang in any subroutine, the problem would be quickly corrected, since the I/O is continually set low and the watchdog timer is allowed to time out, causing a reset or interrupt to be issued. As described in the Watchdog Input Current section, this scheme results in higher time average WDI current than does leaving WDI low for the majority of the timeout period and periodically pulsing it low-high-low.
MAX6316-MAX6322
START
SET WDI HIGH PROGRAM CODE
SUBROUTINE OR PROGRAM LOOP SET WDI LOW
POSSIBLE INFINITE LOOP PATH
RETURN
Figure 10. Watchdog Flow Diagram
__________________Pin Configurations
TOP VIEW
RESET 1 5 VCC RESET 1 5 VCC
Typical Operating Circuit
VIN VCC RESET RESET P I/O GND VCC
GND 2
MAX6316 MAX6320
4 WDI
GND 2
MAX6317
MR 3
MR 3
4 WDI
MAX6316
MANUAL RESET MR GND WDI
SOT23-5
SOT23-5
RESET 1
5 VCC
RESET 1
5 VCC
GND 2
MAX6318 MAX6321
4 WDI
GND 2
MAX6319 MAX6322
4 MR
RESET 3
RESET 3
SOT23-5
SOT23-5
______________________________________________________________________________________
11
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
Table 1. Factory-Trimmed Reset Thresholds
PART MAX63___50_ _-T MAX63___49_ _-T MAX63___48_ _-T MAX63___47_ _-T MAX63___46_ _-T MAX63___45_ _-T MAX63___44_ _-T MAX63___43_ _-T MAX63___42_ _-T MAX63___41_ _-T MAX63___40_ _-T MAX63___39_ _-T MAX63___38_ _-T MAX63___37_ _-T MAX63___36_ _-T MAX63___35_ _-T MAX63___34_ _-T MAX63___33_ _-T MAX63___32_ _-T MAX63___31_ _-T MAX63___30_ _-T MAX63___29_ _-T MAX63___28_ _-T MAX63___27_ _-T MAX63___26_ _-T MAX63___25_ _-T MIN 4.925 7.827 4.728 4.630 4.561 4.433 4.314 4.236 4.137 4.039 3.940 3.842 3.743 3.645 3.546 3.448 3.349 3.251 3.152 3.034 2.955 2.886 2.758 2.660 2.591 2.463 TA = +25C TYP 5.000 4.900 4.800 4.700 4.630 4.500 4.390 4.300 4.200 4.100 4.000 3.900 3.800 3.700 3.600 3.500 3.400 3.300 3.200 3.080 3.000 2.930 2.800 2.700 2.630 2.500 MAX 5.075 4.974 4.872 4.771 4.699 4.568 4.446 4.365 4.263 4.162 4.060 3.959 3.857 3.756 3.654 3.553 3.451 3.350 3.248 3.126 3.045 2.974 2.842 2.741 2.669 2.538 TA = -40C to +85C MIN MAX 4.875 5.125 4.778 5.023 4.680 4.920 4.583 4.818 4.514 4.746 4.388 4.613 4.270 4.490 4.193 4.408 4.095 4.305 3.998 4.203 3.900 4.100 3.803 3.998 3.705 3.895 3.608 3.793 3.510 3.690 3.413 3.588 3.315 3.485 3.218 3.383 3.120 3.280 3.003 3.157 2.925 3.075 2.857 3.000 2.730 2.870 2.633 2.768 2.564 2.696 2.438 2.563
Table 2. Standard Versions
PART MAX6316LUK46CY-T MAX6316LUK29CY-T MAX6316MUK46CY-T MAX6316MUK29CY-T MAX6317HUK46CY-T MAX6318LHUK46CY-T MAX6319LHUK46C-T MAX6320PUK46CY-T MAX6320PUK29CY-T RESET THRESHOLD (V) 4.63 2.93 4.63 2.93 4.63 4.63 4.63 4.63 2.93 MINIMUM RESET TIMEOUT (ms) 140 140 140 140 140 140 140 140 140 TYPICAL WATCHDOG TIMEOUTS (sec) 1.6 1.6 1.6 1.6 1.6 1.6 -- 1.6 1.6 SOT TOP MARK ACDD ACDE ACDF ACDG ACDQ ACDH ACDK ACDN ACDO
Note: Nine standard versions are available, with a required order increment of 2500 pieces. Sample stock is generally held on standard versions only. The required order increment for nonstandard versions is 10,000 pieces. Contact factory for availability. Contact factory for availability of these versions. 12 ______________________________________________________________________________________
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
Table 3. Reset/Watchdog Timeout Periods
RESET TIMEOUT PERIODS SUFFIX A B C D MIN 1 20 140 1.12 TYP 1.6 30 200 1.60 MAX 2 40 280 2.24 sec ms UNITS
__Ordering Information (continued)
PART MAX6319LHUK____-T MAX6319MHUK____-T MAX6320PUK____-T MAX6321HPUK____-T MAX6322HPUK____-T TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 5 SOT23-5 5 SOT23-5 5 SOT23-5 5 SOT23-5 5 SOT23-5
MAX6316-MAX6322
WATCHDOG TIMEOUT W X Y Z 4.3 71 1.12 17.9 6.3 102 1.6 25.6 9.3 ms 153 2.4 38.4 sec
Note: These devices are available with factory-set VCC reset thresholds from 2.5V to 5V, in 0.1V increments. Insert the desired nominal reset threshold (25 to 50, from Table 1) into the blanks following the letters UK. All devices offer factory-programmed reset timeout periods. Insert the letter corresponding to the desired reset timeout period (A, B, C, or D from Table 3) into the blank following the reset threshold suffix. Parts that offer a watchdog feature (see Selector Guide) are factory-trimmed to one of four watchdog timeout periods. Insert the letter corresponding to the desired watchdog timeout period (W, X, Y, or Z from Table 3) into the blank following the reset timeout suffix.
Chip Information
TRANSISTOR COUNT: 191 SUBSTRATE IS INTERNALLY CONNECTED TO V+
______________________________________________________________________________________
13
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
Package Information
SOT5L.EPS
14
______________________________________________________________________________________
5-Pin P Supervisory Circuits with Watchdog and Manual Reset
NOTES
MAX6316-MAX6322
15
______________________________________________________________________________________
5-Pin P Supervisory Circuits with Watchdog and Manual Reset MAX6316-MAX6322
NOTES
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX6316

	To Download MAX6316 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .