September 2008 1 M9999-091608
MIC6315 Micrel
MIC6315
Open-Drain µP Reset Circuit
General Description
The MIC6315 is an inexpensive reset generator circuit that
monitors power supplies in microprocessor based sys-
tems.
The function of this device is to assert a reset if either the
power supply drops below a designated reset threshold
level or /MR is forced low. Several different reset threshold
levels are available to accommodate 3V, 3.3V or 5V powered
systems.
The MIC6315 has an active low, open-drain /RESET output.
The reset output is guaranteed to remain asserted for a
minimum of either 20ms, 140ms, or 1100ms after VCC has
risen above the designed reset threshold level. The MIC6315
comes in a 4-pin SOT-143 package.
Typical Application
VCC
RESET
µP
RESET
VCC
MIC6315
VCC
MR
10k
Features
• Precisionvoltagemonitorfor3V,3.3Vor5Vpowersup-
plies
• /RESETremainsvalidwithVCC as low as 1V
• 5µAsupplycurrent
• 20ms,140ms,or1100msminimumresetpulsewidths
available
• Manualresetinput
• 4-pinSOT-143package
Applications
• Portableequipment
• Intelligentinstruments
• Criticalmicroprocessorpowermonitoring
• Printers/computers
• Embeddedcontrollers
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC6315 Micrel
M9999-091608 2 September 2008
Pin Description
Pin Number Pin Name Pin Function
1 GND ICGroundPin.
2 /RESET /RESET goes low if VCC falls below the reset threshold and remains asserted
for one reset timeout period after VCC exceeds the reset threshold.
3 /MR ManualResetInput.Alogiclowon/MRforcesareset.Theresetwillremain
asserted as long as /MR is held low and for one reset timeout period after /MR goes
high. This input can be shorted to ground via a switch or be driven by TTL or CMOS
logic. Float if unused.
4 VCC PowerSupplyInput.
Pin Conguration
MR
1
2
4V
CC
GND
MIC6315
RESET 3
MIC6315-xxDyU 4-Lead SOT-143
Ordering Information(1, 2)
Standard Pb-Free Nominal Min. tRST Operating
Part Number Marking Part Number Marking VTH (V) (ms) Temp. Range Package
MIC6315-26D2U NY MIC6315-26D2UY NY 2.63 20 –40°C to +85°C 4-lead SOT-143
MIC6315-29D2U NM MIC6315-29D2UY NM 2.93 20 –40°C to +85°C 4-lead SOT-143
MIC6315-30D2U N2 MIC6315-30D2UY N2 3.00 20 –40°C to +85°C 4-lead SOT-143
MIC6315-31D2U NF MIC6315-31D2UY NF 3.08 20 –40°C to +85°C 4-lead SOT-143
MIC6315-40D2U NW MIC6315-40D2UY NW 4.00 20 –40°C to +85°C 4-lead SOT-143
MIC6315-41D2U N6 MIC6315-41D2UY N6 4.10 20 –40°C to +85°C 4-lead SOT-143
MIC6315-44D2U NG MIC6315-44D2UY NG 4.38 20 –40°C to +85°C 4-lead SOT-143
MIC6315-46D2U NQ MIC6315-46D2UY NQ 4.63 20 –40°C to +85°C 4-lead SOT-143
MIC6315-26D3U NR MIC6315-26D3UY NR 2.63 140 –40°C to +85°C 4-lead SOT-143
MIC6315-29D3U NP MIC6315-29D3UY NP 2.93 140 –40°C to +85°C 4-lead SOT-143
MIC6315-30D3U N3 MIC6315-30D3UY N3 3.00 140 –40°C to +85°C 4-lead SOT-143
MIC6315-31D3U NU MIC6315-31D3UY NU 3.08 140 –40°C to +85°C 4-lead SOT-143
MIC6315-40D3U N8 MIC6315-40D3UY N8 4.00 140 –40°C to +85°C 4-lead SOT-143
MIC6315-41D3U N5 MIC6315-41D3UY N5 4.10 140 –40°C to +85°C 4-lead SOT-143
MIC6315-42D3U 0N MIC6315-42D3UY 0N 4.20 140 –40°C to +85°C 4-lead SOT-143
MIC6315-44D3U NH MIC6315-44D3UY NH 4.38 140 –40°C to +85°C 4-lead SOT-143
MIC6315-46D3U NX MIC6315-46D3UY NX 4.63 140 –40°C to +85°C 4-lead SOT-143
MIC6315-26D4U NS MIC6315-26D4UY NS 2.63 1100 –40°C to +85°C 4-lead SOT-143
MIC6315-29D4U NN MIC6315-29D4UY NN 2.93 1100 –40°C to +85°C 4-lead SOT-143
MIC6315-30D4U N4 MIC6315-30D4UY N4 3.00 1100 –40°C to +85°C 4-lead SOT-143
MIC6315-31D4U 2N MIC6315-31D4UY 2N 3.08 1100 –40°C to +85°C 4-lead SOT-143
MIC6315-40D4U M9 MIC6315-40D4UY M9 4.00 1100 –40°C to +85°C 4-lead SOT-143
MIC6315-41D4U M7 MIC6315-41D4UY M7 4.10 1100 –40°C to +85°C 4-lead SOT-143
MIC6315-44D4U NJ MIC6315-44D4UY NJ 4.38 1100 –40°C to +85°C 4-lead SOT-143
MIC6315-46D4U NZ MIC6315-46D4UY NZ 4.63 1100 –40°C to +85°C 4-lead SOT-143
Notes:
1. Alldevicesavailableintapeandreelonly.
2. Partsnotyetassignedanidenticationcodeareshownas“zz”.ContactMicrelfordetails.Minimumordermayapply.
September 2008 3 M9999-091608
MIC6315 Micrel
Electrical Characteristics
For typical values, VCC = 2.5V to 5.5V, TA = 25°C; bold valuesindicate–40°C≤TA≤+85°C;unlessnoted
Symbol Parameter Condition Min Typ Max Units
VCC Operating Voltage Range 1 5.5 V
ICC Supply Current VCC = 5.5V, no load 5 15 µA
V
CC = 3.6V, no load 5 10 µA
VTH Reset Voltage Threshold Note 4 VTH–2.5% V
TH VTH+2.5% V
tRST ResetTimeoutPeriod D2U 20 28 44 ms
D3U 140 200 320 ms
D4U 1100 1500 2500 ms
VOL /RESET Output Voltage VCC≥4.0V,ISINK=3.2mA 0.4 V
V
CC > 2.5V, ISINK=1.2mA 0.3 V
V
CC≥1.0V,ISINK=50µA 0.3 V
/RESET Output Leakage /RESET deasserted 1 µA
/MRMinimumPulseWidth 10 µs
/MRtoResetDelay 0.5 µs
VIH /MR Input Threshold VTH > 4.0V 2.3 V
V
TH < 4.0V 0.7×VCC V
VIL /MR Input Threshold VTH > 4.0V 0.8 V
V
TH < 4.0V 0.25×VCC V
/MRPull-UpResistance 10 20 30 kΩ
/MR Glitch Immunity 100 ns
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
4. Various reset thresholds available. See ordering information or contact factory.
Absolute Maximum Ratings(1)
Terminal Voltage
(VCC, /RESET) ........................................–0.3V to 6.0V
(/MR) ..........................................–0.3V to (VCC + 0.3V)
Rate of Rise (VCC) .................................................. 100V/µs
Input Current (VCC, /MR) ............................................ 20mA
Output Current (/RESET) ........................................... 20mA
Lead Temperature (soldering, 10 sec.) ...................... 300°C
Storage Temperature (TS) ......................... –65°C to 150°C
ESD Rating(3) ............................................................... 3kV
Operating Ratings(2)
Operating Temperature Range ................... –40°C to +85°C
Input Voltage (/RESET) .................................... GND – 5.5V
PowerDissipation(TA = +70°C) .............................. 320mW
MIC6315 Micrel
M9999-091608 4 September 2008
Functional Diagram
+
-
Reset
Threshold (V)
VCC (4) RESET (2)
GND (1)
RESET
GENERATOR
MR (3)
Timing Diagram
VCC
/MR
/RESET
tRST tRST
VTH
Reset Timing Diagram
September 2008 5 M9999-091608
MIC6315 Micrel
Applications Information
Microprocessor Reset
The /RESET pin is asserted whenever VCC falls below the
reset threshold voltage or if /MR (manual reset) is forced
low. The /RESET pin remains asserted for the duration of
the reset timeout period after VCC has risen above the reset
threshold or /MR has returned high. The reset function en-
sure the microprocessor is properly reset and powers up in
a known condition after a power failure. /RESET will remain
valid with VCC as low as 1V.
The /RESET output is a simple open-drain N-channel MOS-
FETstructure.Apull-up resistormust beused topull this
output up to some voltage. For most applications, this volt-
age will be the same power supply that supplies VCC to the
MIC6315. It is possible, however, to tie this resistor to some
other voltage. This will allow the MIC6315 to monitor one
voltage while level-shifting the /RESET output to some other
voltage. The pull-up voltage must be limited to 6.0V or less
(absolute maximum) to avoid damage to the MIC6315. The
resistor must be small enough to supply current to the inputs
and leakage paths that are driven by the /RESET output.
/RESET Valid at Low Voltage
AsVCC drops to 0V, the MIC6315 will no longer be able to
pullthe/RESEToutputlow.Atthispoint,thepull-upresistor
will pull the output high. The value of the pull-up resistor and
the voltage it is connected to will affect the point at which
this happens.
Wire OR'ing The /RESET Output
Because the RESET output is open-drain, several reset
sources can be wire-ORed, in parallel, to allow resets from
multiple sources.
VCC Transients
The MIC6315 is relatively immune to negative-going VCC
glitches below the reset threshold. Typically, a negative-going
transient 125mV below the reset threshold with a duration of
20µsorlesswillnotcauseanunwantedreset.Ifadditional
transient immunity is needed, a bypass capacitor can be
placed a close as possible to the MIC6315.
VCC
RESET
5V SYSTEM
RESET
VCC
MIC6315
+5.0V
MR
10k
+3.3V
MIC6315 Used in a Multiple Supply System
MIC6315 Micrel
M9999-091608 6 September 2008
Package Information
0.150 (0.0059)
0.089 (0.0035)
8
0
0.400 (0.016) TYP 3 PLACES
2.50 (0.098)
2.10 (0.083)
1.40 (0.055)
1.20 (0.047)
0.950 (0.0374) TYP
3.05 (0.120)
2.67 (0.105)
0.800 (0.031) TYP
1.12 (0.044)
0.81 (0.032)
0.10 (0.004)
0.013 (0.0005)
DIMENSIONS:
MM (INCH)
0.41 (0.016)
0.13 (0.005)
C
L
C
L
4-Pin SOT-143 (U)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
tel + 1 (408) 944-0800 fa x + 1 (408) 474-1000 w e b http://www.micrel.com
The information furnished by Micrel in this datasheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use.
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