19-2000; Rev 2; 1/00
Open-Drain SOT µP Reset Circuit
________________General Description
The MAX6315 low-power CMOS microprocessor (µP)
supervisory circuit is designed to monitor power sup-
plies in µP and digital systems. It provides excellent cir-
cuit reliability and low cost by eliminating external
components and adjustments. The MAX6315 also pro-
vides a debounced manual reset input.
This device performs a single function: it asserts a reset
signal whenever the V
CC
supply voltage falls below a
preset threshold or whenever manual reset is asserted.
Reset remains asserted for an internally programmed
interval (reset timeout period) after V
CC
has risen above
the reset threshold or manual reset is deasserted. The
MAX6315’s open-drain
RESET
output can be pulled up
to a voltage higher than V
CC
.
The MAX6315 comes with factory-trimmed reset thresh-
old voltages in 100mV increments from 2.5V to 5V.
Preset timeout periods of 1ms, 20ms, 140ms, and
1120ms (min) are also available. The device comes in a
SOT143 package.
For microcontrollers (µCs) and µPs with bidirectional
reset pins, see the MAX6314 data sheet.
____________________________Features
o
Small SOT143 Package
o
Open-Drain
RESET
Output Can Exceed V
CC
o
Precision, Factory-Set V
CC
Reset Thresholds:
100mV Increments from 2.5V to 5V
o
Four Reset Timeout Periods Available:
1ms, 20ms, 140ms, or 1120ms (minimum)
o
Immune to Short V
CC
Transients
o
5µA Supply Current
o
Pin-Compatible with MAX811
o
Guaranteed Over Temperature
MAX6315
________________________Applications
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
Ordering and Marking Information appear at end of
data sheet.
__________Typical Operating Circuit
V
CC
__________________Pin Configuration
V
CC
LASER-
TRIMMED
RESISTORS
TOP VIEW
GND
1
4
V
CC
µP
MAX6315
MR
RESET
CIRCUITRY
RESET
RESET
RESET
2
3
MR
MAX6315
GND
SOT143
________________________________________________________________
Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Open-Drain SOT µP Reset Circuit
MAX6315
ABSOLUTE MAXIMUM RATINGS
V
CC
........................................................................-0.3V to +6.0V
RESET....................................................................-0.3V
to +6.0V
All Other Pins..............................................-0.3V to (V
CC
+ 0.3V)
Input Current (V
CC
) .............................................................20mA
Output Current (RESET)......................................................20mA
Rate of Rise (V
CC
) ...........................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
SOT143 (derate 4mW/°C above +70°C) ........................320mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +160°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
(V
CC
= +2.5V to +5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Operating Voltage Range
SYMBOL
V
CC
CONDITIONS
MIN
TYP
5
4
V
TH
MAX
5.5
12
15
10
12
V
TH
+ 1.8%
V
TH
+ 2.5%
V
TH
+ 3.5%
UNITS
V
T
A
= -40°C to +85°C
1.0
V
CC
= 5.5V, no load (-40°C to +85°C)
V
CC
= 5.5V, no load (-40°C to +125°C)
V
CC
= 3.6V, no load (-40°C to +85°C)
V
CC
= 3.6V, no load (-40°C to +125°C)
T
A
= +25°C
V
TH
- 1.8%
T
A
= -40°C to +85°C
V
TH
- 2.5%
T
A
= -40°C to +125°C
V
TH
- 3.5%
V
CC
= falling at 1mV/µs
MAX6315US_ _D1-T (-40°C to +85°C)
MAX6315US_ _D1-T (-40°C to +125°C)
MAX6315US_ _D2-T (-40°C to +85°C)
MAX6315US_ _D2-T (-40°C to +125°C)
MAX6315US_ _D3-T (-40°C to +85°C)
MAX6315US_ _D3-T (-40°C to +125°C)
MAX6315US_ _D4-T (-40°C to +85°C)
MAX6315US_ _D4-T (-40°C to +125°C)
V
CC
Supply Current
I
CC
µA
Reset Threshold (Note 1)
Reset Threshold Tempco
V
CC
to Reset Delay
V
TH
∆V
TH
/°C
V
ppm/°C
µs
Reset Timeout Period
t
RP
1
0.8
20
16
140
112
1120
896
0.8
60
35
1.4
28
200
1570
2
2.4
40
48
280
336
2240
2688
ms
MANUAL RESET INPUT
MR
Input Threshold
MR
Minimum Input Pulse
MR
Glitch Rejection
MR
to Reset Delay
MR
Pull-Up Resistance
V
CC
> 4.25V, I
SINK
= 3.2mA
RESET
Output Voltage
V
OL
V
CC
> 2.5V, I
SINK
= 1.2mA
V
CC
> 1.2V, I
SINK
= 0.5mA
V
CC
> 1.0V, I
SINK
= 80µA
RESET
Output Leakage Current
V
CC
> V
TH
,
RESET
deasserted
0.3
1
µA
32
V
IL
V
IH
V
IL
V
IH
V
TH
> 4.0V
V
TH
< 4.0V
2.4
0.3 x V
CC
0.7 x V
CC
1
100
500
63
100
0.4
0.3
V
µs
ns
ns
kΩ
V
Note 1:
The MAX6315 monitors V
CC
through an internal factory-trimmed voltage divider that programs the nominal reset threshold.
Factory-trimmed reset thresholds are available in 100mV increments from 2.5V to 5V (see
Ordering Information).
2
_______________________________________________________________________________________
Open-Drain SOT µP Reset Circuit
__________________________________________Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6315-01
MAX6315-02
MAX6315
SUPPLY CURRENT vs. TEMPERATURE
6
5
SUPPLY CURRENT (µA)
4
3
V
CC
= 3V
2
1
0
-50
-30
-10
10
30
50
70
90
TEMPERATURE (°C)
V
CC
= 1V
V
CC
= 5V
6
5
SUPPLY CURRENT (µA)
4
3
POWER-DOWN RESET DELAY
vs. TEMPERATURE
V
CC
FALLING AT 1mV/µs
POWER-DOWN RESET DELAY (µs)
40
V
TH
= 4.63V
MAX6315-03
50
T
A
= +85°C
30
T
A
= +25°C
2
1
0
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
T
A
= -40°C
20
V
TH
= 3.00V
10
0
-50
-30
-10
10
30
50
70
90
TEMPERATURE (°C)
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE (V
CC
RISING)
MAX6315-04
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE (V
CC
FALLING)
MAX6315-05
MAXIMUM TRANSIENT DURATION
vs. RESET COMPARATOR OVERDRIVE
MAXIMUM TRANSIENT DURATION (µs)
T
A
= +25°C
RESET OCCURS
ABOVE CURVE
V
TH
= 4.63V
60
MAX6315-06
1.04
NORMALIZED RESET TIMEOUT PERIOD
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
-50
-30
-10
10
30
50
70
1.006
NORMALIZED RESET THRESHOLD
1.004
1.002
1.000
0.998
0.996
0.994
100
80
40
20
V
T
= 3.00V
0
10
100
RESET COMP. OVERDRIVE, V
TH
- V
CC
(mV)
1000
90
-50
-30
-10
10
30
50
70
90
TEMPERATURE (°C)
TEMPERATURE (°C)
______________________________________________________________Pin Description
PIN
1
2
3
4
NAME
GND
RESET
MR
V
CC
Ground
Active-Low Open-Drain Output. Connect to an external pull-up resistor. Can be pulled up to a voltage
higher than V
CC
, but less than 6V.
Manual Reset Input. A logic low on
MR
asserts reset. Reset remains asserted as long as
MR
is low, and
for the reset timeout period (t
RP
) after the reset conditions are terminated. Connect to V
CC
if not used.
Supply Voltage and Reset Threshold Monitor Input
FUNCTION
_______________________________________________________________________________________
3
Open-Drain SOT µP Reset Circuit
MAX6315
_______________Detailed Description
Reset Output
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX6315 asserts reset to prevent
code-execution errors during power-up, power-down,
or brownout conditions.
RESET
is guaranteed to be a
logic low for V
CC
> 1V (see
Electrical Characteristics).
Once V
CC
exceeds the reset threshold, the internal
timer keeps reset asserted for the reset timeout period
(t
RP
); after this interval
RESET
goes high. If a brownout
condition occurs (monitored voltage dips below its pro-
grammed reset threshold),
RESET
goes low. Any time
V
CC
dips below the reset threshold, the internal timer
resets to zero and
RESET
goes low. The internal timer
starts when V
CC
returns above the reset threshold, and
RESET
remains low for the reset timeout period.
The MAX6315’s
RESET
output structure is a simple
open-drain N-channel MOSFET switch. Connect a pull-
up resistor to any supply in the 0V to +6V range. Select
a resistor value large enough to register a logic low
when
RESET
is asserted (see
Electrical Characteristics),
and small enough to register a logic high while supply-
ing all input current and leakage paths connected to the
RESET
line. A 10kΩ pull-up is sufficient in most applica-
tions.
Often, the pull-up connected to the MAX6315’s
RESET
output will connect to the supply voltage monitored at
the IC’s V
CC
pin. However, some systems may use the
open-drain output to level-shift from the monitored sup-
ply to reset circuitry powered by some other supply
(Figure 1). This is one useful feature of an open-drain
output. Keep in mind that as the MAX6315’s V
CC
decreases below 1V, so does the IC’s ability to sink
current at
RESET.
Finally, with any pull-up,
RESET
will
be pulled high as V
CC
decays toward 0V. The voltage
where this occurs depends on the pull-up resistor value
and the voltage to which it connects (see
Electrical
Characteristics).
+3.3V
+5.0V
V
CC
10k
MR
RESET
5V SYSTEM
MAX6315
GND
Figure 1. MAX6315 Open-Drain
RESET
Output Allows Use
with Multiple Supplies
If
MR
is driven from long cables or if the device is used
in a noisy environment, connecting a 0.1µF capacitor
from
MR
to ground provides additional noise immunity.
__________Applications Information
Negative-Going V
CC
Transients
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, these devices
are relatively immune to short-duration negative-going
transients (glitches). The
Typical Operating Character-
istics
show the Maximum Transient Duration vs. Reset
Threshold Overdrive, for which reset pulses are not
generated. The graph was produced using negative-
going pulses, starting at V
RST
max and ending below
the programmed reset threshold by the magnitude indi-
cated (reset threshold overdrive). The graph shows the
maximum pulse width that a negative-going V
CC
tran-
sient may typically have without causing a reset pulse
to be issued. As the transient amplitude increases (i.e.,
goes farther below the reset threshold), the maximum
allowable pulse width decreases. A 0.1µF bypass
capacitor mounted close to V
CC
provides additional
transient immunity.
Manual-Reset Input
Many µP-based products require manual-reset capabil-
ity, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. A logic low on
MR
asserts reset. Reset remains asserted while
MR
is low,
and for the reset active timeout period after
MR
returns
high.
MR
has an internal 63kΩ pull-up resistor, so it can be
left open if not used. Connect a normally open momen-
tary switch from
MR
to GND to create a manual reset
function; external debounce circuitry is not required.
4
_______________________________________________________________________________________
Open-Drain SOT µP Reset Circuit
________________________________________________________Ordering Information
PART
†
MAX6315US50D1-T
MAX6315US49D1-T
MAX6315US48D1-T
MAX6315US47D1-T
MAX6315US46D1-T
MAX6315US45D1-T
MAX6315US44D1-T
†††
MAX6315US43D1-T
MAX6315US42D1-T
MAX6315US41D1-T
MAX6315US40D1-T
MAX6315US39D1-T
MAX6315US38D1-T
MAX6315US37D1-T
MAX6315US36D1-T
MAX6315US35D1-T
MAX6315US34D1-T
MAX6315US33D1-T
MAX6315US32D1-T
MAX6315US31D1-T
MAX6315US30D1-T
MAX6315US29D1-T
MAX6315US28D1-T
MAX6315US27D1-T
MAX6315US26D1-T
†††
MAX6315US25D1-T
NOMINAL
V
TH
(V)
5.00
4.90
4.80
4.70
4.63
4.50
4.39
4.30
4.20
4.10
4.00
3.90
3.80
3.70
3.60
3.50
3.40
3.30
3.20
3.08
3.00
2.93
2.80
2.70
2.63
2.50
MIN t
RP
(ms)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
SOT TOP
MARK
††
FX_ _
FY_ _
FZ_ _
GA_ _
GB_ _
GC_ _
GD_ _
GE_ _
GF_ _
GG_ _
GH_ _
GI_ _
GJ_ _
GK_ _
GL_ _
GM_ _
GN_ _
GO_ _
GP_ _
GQ_ _
GR_ _
GS_ _
GT_ _
GU_ _
GV_ _
GW_ _
PART
†
MAX6315US50D2-T
MAX6315US49D2-T
MAX6315US48D2-T
MAX6315US47D2-T
MAX6315US46D2-T
MAX6315US45D2-T
MAX6315US44D2-T
†††
MAX6315US43D2-T
MAX6315US42D2-T
MAX6315US41D2-T
MAX6315US40D2-T
MAX6315US39D2-T
MAX6315US38D2-T
MAX6315US37D2-T
MAX6315US36D2-T
MAX6315US35D2-T
MAX6315US34D2-T
MAX6315US33D2-T
MAX6315US32D2-T
MAX6315US31D2-T
MAX6315US30D2-T
MAX6315US29D2-T
MAX6315US28D2-T
MAX6315US27D2-T
MAX6315US26D2-T
†††
MAX6315US25D2-T
NOMINAL
V
TH
(V)
5.00
4.90
4.80
4.70
4.63
4.50
4.39
4.30
4.20
4.10
4.00
3.90
3.80
3.70
3.60
3.50
3.40
3.30
4.20
3.08
3.00
2.93
2.80
2.70
2.63
2.50
MIN t
RP
(ms)
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
SOT TOP
MARK
††
GX_ _
GY_ _
GZ_ _
HA_ _
HB_ _
HC_ _
HD_ _
HE_ _
HF_ _
HG_ _
HH_ _
HI_ _
HJ_ _
HK_ _
HL_ _
HM_ _
HN_ _
HO_ _
HP_ _
HQ_ _
HR_ _
HS_ _
HT_ _
HU_ _
HV_ _
HW_ _
MAX6315
†
The MAX6315 is available in a SOT143 package, -40°C to +125°C temperature range.
††
The first two letters in the package top mark identify the part, while the remaining two letters are the lot tracking code.
†††
Sample stocks generally held on the bolded products; also, the bolded products have 2,500 piece minimum-order quantities.
Non-bolded products have 10,000 piece minimum-order quantities. Contact factory for details.
Note:
All devices available in tape-and-reel only. Contact factory for availability.
_______________________________________________________________________________________
5
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