MICREL MIC2753

MIC2753/2754
Micrel
MIC2753/2754
Power Supply Supervisors
Preliminary Information
General Description
Features
The MIC2753 and MIC2754 are ultraminiature, full-featured,
power supply supervisors featuring active-high and activelow reset outputs, respectively.
•
•
•
•
•
Undervoltage and overvoltage monitor
Separate overvoltage flag output
Generates 140ms (minimum) power-on reset pulse
Debounced manual reset input
Choice of active-high (MIC2753) or
active-low (MIC2754) reset outputs
• Low 30µA typical supply current
• No external components needed
• IttyBitty™ SOT-23-5 package
The MIC2753/4 includes an undervoltage detector with a
power-on reset generator and reset output, an overvoltage
detector with a separate output for activating crowbar circuits,
and a debounced manual reset input. Typical supply current
is a low 30µA.
These devices provide a 140ms minimum reset output at
power-on and assert their reset outputs any time the input
voltage deviates beyond preset overvoltage or undervoltage
thresholds. Reset outputs remain asserted for 140ms (minimum) after the input returns to normal or after releasing the
manual reset. When an overvoltage condition is detected, the
overvoltage output is immediately activated. Hysteresis on
both thresholds prevents erratic operation due to noise.
Applications
•
•
•
•
Computer systems
Embedded controllers
Power supplies
Telecommunications systems
Typical Application
VCC
Fuse
Microcontroller
MIC2754
Manual
Reset
VIN
RST
MR
HV
VCC
GND
RST IN
SCR
Crowbar
GND
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
June 1999
1
MIC2753/2754
MIC2753/2754
Micrel
Ordering Information
Part Number
Mark
Lower Threshold
Voltage
Monitored
Voltage*
Upper Threshold
Voltage
Reset
Temperature
Range
Package
MIC2753-RBM5
UDR
2.63V
2.85V±5%
3.08V
Active High
–40°C to +85°C
SOT-23-5
MIC2753-SBM5
UDS
2.93V
3.3V±10%
3.83V
Active High
–40°C to +85°C
SOT-23-5
MIC2753-TBM5
UDT
3.08V
3.3V±5%
3.53V
Active High
–40°C to +85°C
SOT-23-5
MIC2753-MBM5
UDM
4.38V
5.0V±10%
5.81V
Active High
–40°C to +85°C
SOT-23-5
MIC2753-LBM5
UDL
4.63V
5.0V±5%
5.38V
Active High
–40°C to +85°C
SOT-23-5
MIC2754-RBM5
UER
2.63V
2.85V±5%
3.08V
Active Low
–40°C to +85°C
SOT-23-5
MIC2754-SBM5
UES
2.93V
3.3V±10%
3.83V
Active Low
–40°C to +85°C
SOT-23-5
MIC2754-TBM5
UET
3.08V
3.3V±5%
3.53V
Active Low
–40°C to +85°C
SOT-23-5
MIC2754-MBM5
UEM
4.38V
5.0V±10%
5.81V
Active Low
–40°C to +85°C
SOT-23-5
MIC2754-LBM5
UEL
4.63V
5.0V±5%
5.38V
Active Low
–40°C to +85°C
SOT-23-5
* Contact factory for voltages not listed.
Pin Configuration
VIN HV RST
3
2
VIN GND HV
1
3
Part
Identification
UDx
2
1
UEx
4
5
4
5
GND
MR
RST
MR
MIC2753
Voltage
Code
MIC2754
Pin Description
Pin No.
MIC2753
Pin No.
MIC2754
1
Pin Name
Pin Function
RST
Reset (Digital Output): Active-high output. Asserted when VIN falls below
VTHU (undervoltage threshold), or rises above VTHO (overvoltage threshold).
Deasserted no less than 140ms after VIN returns within threshold limits.
2
1
/HV
High-Voltage Flag (Open-Drain Output): /HV is asserted (active low) when
the input voltage exceeds the VTHO (overvoltage threshold). It indicates
power supply overvoltage and is intended for connection to a protection
device such as a “crowbar” circuit.
3
3
VIN
Analog Input: Voltage monitor input and power supply input to the IC.
4
/RST
Reset (Digital Output): Active-low digital output. This output will be asserted
whenever VIN falls below VTHU (undervoltage threshold), or rises above
VTHO (overvoltage threshold). It will be deasserted no less than 140ms after
VIN returns within the threshold limits.
4
2
GND
Ground: Ground return for all IC functions.
5
5
/MR
Manual Reset (Digital Input): Logic low initiates immediate, unconditional
reset. If VIN is within tolerance thresholds, when /MR is released (returns
high), the reset output(s) will be deasserted no less than 140ms later. /MR
may be driven by a CMOS or TTL logic signal or a mechanical switch.
(Switch debouncing is performed internally.) /MR has an internal pull-up to
VIN and may remain open if unused.
MIC2753/2754
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June 1999
MIC2753/2754
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (VIN) ...................................... –0.3V to 10V
Reset Voltage (VRST) ........................... –0.3V to VIN + 0.3V
Manual Reset Voltage (VMR) ............... –0.3V to VIN + 0.3V
Reset Current (IRST) ................................................... 10mA
Continuous Power Dissipation
(PD at TA = +85°C) .............................................. 200mW
Storage Temperature (TS) ....................... –65°C to +150°C
ESD Rating, Note 3
Supply Voltage (VIN) .......................................... 1.5V to 7V
Ambient Temperature (TA) ......................... –40°C to +85°C
Junction Temperature (TJ) ........................................ 150°C
Manual Reset (VMR) ............................................. 0V to VIN
Thermal Resistance
(θJA) ................................................................... 325°C/W
Electrical Characteristics
VIN = 5.0V (L, M voltage code), VIN = 3.3V (T, S voltage code), VIN = 2.85 (R voltage code) TA = 25°C;
bold values indicate 1.5V ≤ VIN ≤ 7.0V, –40°C ≤ TA ≤ +85°C Note 4; unless noted
Symbol
Parameter
VIN
Input Supply Voltage
IDD
Operating Supply Current
manual reset not asserted
VTHO
Overvoltage Threshold
L voltage code
VTHU
Undervoltage Threshold
Condition
Min
Typ
Max
Units
7.0
V
30
100
µA
5.28
5.38
6.00
V
M voltage code
5.62
5.81
6.00
V
T voltage code
3.459
3.53
3.96
V
S voltage code
3.67
3.83
3.96
V
R voltage code
3.018
3.08
3.28
V
L voltage code
4.50
4.63
4.75
V
M voltage code
4.25
4.38
4.50
V
T voltage code
3.00
3.08
3.15
V
S voltage code
2.85
2.93
3.00
V
R voltage code
2.55
2.63
2.70
V
1.0
VHYST+
Overvoltage Threshold Hysteresis
–15
mV
VHYST–
Undervoltage Threshold Hysteresis
+15
mV
tPROP(RST) Propagation Delay
tRST
June 1999
VIN = VTHO (min) – 100mV to VTHO (max) + 100mV
12
30
µs
VIN = VTHU (max) + 100mV to VTHU (min) – 100mV
12
30
µs
240
560
ms
Reset Pulse Width
140
3
MIC2753/2754
MIC2753/2754
Micrel
Symbol
Parameter
Condition
VOL(RST)
Reset Output Voltage Low
MIC2753
VOH(RST)
Reset Output Voltage High
MIC2753
/Reset Output Voltage Low
MIC2754
VOL(RST)
/Reset Output Voltage High
MIC2754
VOH(RST)
Min
Typ
Max
Units
R/S/T voltage codes,
VIN = VTHU(max) + 100mV, ISINK = 50µA
0.5
V
L/M voltage codes,
VIN = VTHU(max) + 100mV, ISINK = 50µA
0.5
V
R/S/T voltage codes,
VIN = VTHU(min) – 100mV, ISOURCE = 0.5mA
VIN –0.5
V
L/M voltage codes,
VIN = VTHU(min) – 100mV, ISOURCE = 1.0mA
VIN –0.8
V
R/S/T voltage codes,
VIN = VTHU(min) – 100mV, ISINK = 0.5mA
0.5
V
L/M voltage codes,
VIN = VTHU(min) – 100mV, ISINK = 1.0mA
0.8
V
VIN ≥ 1.5V, IOL = 50µA
0.5
V
R/S/T voltage codes,
VIN = VTHU(max) + 100mV, ISOURCE = 35µA
VIN –0.5
V
L/M voltage codes,
VIN = VTHU(max) + 100mV, ISOURCE = 35µA
VIN –0.5
V
0.8 VIN
V
VIH(/MR)
/MR Input Voltage, High
VIL(/MR)
/MR Input Voltage, Low
tPROP(/MR)
Propagation Delay
MIC2753
V/MR ≤ VIL to VRST ≥ VOH
Propagation Delay
MIC2754
V/MR ≤ VIL to V/RST ≤ VOL
0.2 VIN
V
1
2
µs
1
2
µs
µs
t/MR(min)
/MR Minimum Input Pulse Width
2.5
IPU
Pull-Up Current, /MR
V/MR = 0V
0.2
IIH
Input Current, /MR
V/MR = VIN
0.01
VOL(/HV)
/HV Output Voltage Low
VIN > VTHO(max),
ISINK = 0.5mA, R/S/T voltage codes
0.5
V
V
VIN > VTHO(max),
ISINK = 1.0mA, L/M voltage codes
0.8
V
V
30
µs
+2
µA
tPROP(/HV)
/HV Propagation Delay
VIN = VTHO (min) – 100mV to VTHO (max) + 100mV
I/HV
/HV Leakage Current
VIN = VTHO (min) – 100mV
12
–2
µA
2
µA
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions recommended.
Note 4.
Final test on outgoing product is performed at TA = 25°C. Device performance over –40°C ≤ TA ≤ +85°C is guaranteed by design.
MIC2753/2754
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June 1999
MIC2753/2754
Micrel
Typical Characteristics
Supply Current
vs. Temperature
Power-Down Reset Delay
vs. Temperature
40
2V 3V 4V
5V
20
1V
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
7
6
5
4
3
2
1
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Normalized Reset Threshold
vs. Temperature
RESET DELAY (ns)
1.000
0.995
40
35
30
25
0.990
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
50
20mV
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Overdrive = 200mV
10
L, M voltage codes
300
PULL-UP CURRENT (nA)
20
100mV
20
MR Pull-up Current
vs. Temperature
1.005
Overdrive = 10mV
20mV
Normalized Overvoltage
Threshold vs. Temperature
1.010
40
10mV
30
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
L, M voltage codes
THRESHOLD
UNDERVOLTAGE DELAY (µs)
Overvoltage Delay
vs. Temperature
20
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Undervoltage Delay
vs. Temperature
June 1999
150
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
40
45
1.005
10
200
50
L, M voltage codes
30
250
Manual Reset Delay
vs. Temperature
1.010
NORMALIZED THRESHOLD
L, M voltage codes
RESET PULSE WIDTH (ms)
VIN = 6V
60
9
8
OVERVOLTAGE DELAY (µs)
80
300
10
No Load; L, M
voltage codes
RESET DELAY (µs)
SUPPLY CURRENT (µA)
100
Power-Up Reset Timeout
vs. Temperature
1.000
0.995
0.990
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
5
260
220
5.0V
180
140
100
60
3.3V
2.85V
20
-40 -20 0 20 40 60 80 100
TEMPERATURE (˚C)
MIC2753/2754
MIC2753/2754
Micrel
Functional Diagram
MR
Delay
Line
VIN
RST (MIC2753 only)
350ms typ.
Low-Voltage
Detect
S Q
RST (MIC2754 only)
R Q
High-Voltage
Detect
HV
1.2V
Bandgap
Reference
GND
MIC2753/2754
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June 1999
MIC2753/2754
Micrel
Timing Diagram
A
VTHO
VHYST+
VIN(nominal)
VHYST–
VIN VTHU
A
1.5V
0V
tRESET
VOH
VRST
B
(MIC2754) V
OL
tRESET
tPROP
VOH
VRST
tRESET
tPROP
B
(MIC2753) VOL
VOH
B
HV
VOL
A. Very short transients will be ignored by the
MIC275x. See “Applications Information.”
B. Without external pull-down or pull-up resistors, the
output is not guaranteed to be valid when VIN < 1.5V.
Manual Reset Timing
VIH
VMR
VIL
tRESET
VRST
VOH
VOL
(MIC2754)
VRST
tPROP(MR)
VOH
VOL
(MIC2753)
June 1999
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MIC2753/2754
MIC2753/2754
Micrel
no less than 140ms later. /MR may be driven by a CMOS or
TTL logic signal or a mechanical switch. Typically, a momentary push-button switch is connected such that /MR is shorted
to ground when the contacts close. Switch debouncing is
performed internally; the switch may be connected directly
between /MR and GND. /MR has an internal pull-up to VIN
and may be left open if unused.
Overvoltage Output
Functional Description
The MIC275x family of devices are typically used to monitor
power supplies of intelligent circuits such as microcontrollers
and microprocessors. By connecting the appropriate reset
output of an MIC275x to the reset input of a microcontroller or
microprocessor, the processor will be properly reset at poweron, and during power-down and brownout conditions. In
addition, asserting /MR (manual reset input) activates the
reset function.
The /HV and reset outputs are immediately and unconditionally asserted any time VIN exceeds VTHO (overvoltage threshold). /HV is an active-low, open-drain logic output. Overvoltage on a system power supply rail is generally considered to
be a catastrophic condition which may cause permanent
system damage. If and when an overvoltage condition occurs
using a MIC275x, the system is immediately driven into reset
mode and /HV (overvoltage flag), is driven active.
Typically, an overvoltage signal, such as /HV, is connected to
a “crowbar circuit” using a latching power device such as an
SCR. See “Typical Application”. The crowbar circuit will
clamp the power rail to some low voltage by shunting power
supply current to ground. This should cause some upstream
power supply protection device to be activated, such as foldback current limiting, a fuse, or circuit breaker. In this way, the
system is most likely to be protected against damage and
spurious operation until the condition can be remedied. /HV
is an open-drain output and may be wire-ORed with other
open-drain logic signals. Some systems may require a pullup resistor.
Reset Outputs
The /RST and/or RST output is asserted any time /MR is
asserted or if VIN deviates beyond the preset threshold
voltages, VTHU and VTHO. Reset output(s) remain asserted
for 140ms minimum after VIN returns within the threshold
boundaries and/or /MR is released. A minimum 140ms reset
pulse is also generated at power-on. Hysteresis is included in
the overvoltage and undervoltage comparators to prevent
chattering of the outputs due to noise.
The MIC275x family offers a choice of two reset output
options: the MIC2753 has an active-high RST output, and the
MIC2754 has an active-low /RST output.
Manual Reset Input
The ability to initiate a reset from external logic or a manual
switch is provided in addition to the MIC275x’s automatic
supervisory functions. Driving the /MR input low causes an
immediate and unconditional reset to occur. Assuming VIN is
within the tolerance thresholds when /MR is released (internally pulled to logic high), the reset output will be deasserted
System Block Diagram
Reset
Switch
HV
Voltage Monitor
and
Reset Generator
Crowbar
Circuit
Microprocessor
System
Circuitry
Reset(s)
MIC2753/2754
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June 1999
MIC2753/2754
Micrel
undesired operation. (In most cases, however, it is expected
that the circuits driven by the MIC2754 will be similarly
inoperative at VCC ≤ 1.5V.)
If a given application requires that /RST be valid below VIN =
1.5V, this can be accomplished by adding a pull-down resistor to the /RST output. A value of 100kΩ is recommended as
this is usually an acceptable compromise of leakage current
and pull-down current. The resistor’s value is not critical,
however.
Application Information
Supply Transients
The MIC2753/4 are inherently immune to very short “glitches”
on VIN. In the case of very brief transients, VIN may drop
below the reset threshold or exceed the overvoltage threshold without activating the RST, /RST or /HV output. As shown
in the graphs of Figure 1, the narrower the transient, the
deeper the threshold overdrive that will be ignored by the
MIC2753/4. The lines on the graph represent the typical
allowable transient duration for a given amount of threshold
overdrive that will not generate a reset or overvoltage indication. The data from which Figure 1 is derived was taken by
adding negative-going square-wave pulses to a dc VIN set at
0.5V above or below the actual measured threshold for the
part being characterized.
In the case of the MIC2754L/M for example (refer to Figure 1),
a transient on VIN which goes below the reset threshold by
100mV and lasts no more than 8.4µs will typically not cause
a reset to occur. Bypass capacitance placed as close as
physically possible to the device’s VIN and GND pins will
increase the transient immunity (0.1µF, for example).
Ensuring Proper Operation at Low Supply
The statements above also apply to the MIC2753’s RST
output. That is, to ensure valid RST signal levels at VIN < 1.5V,
a pull-up resistor (as opposed to a pull-down) should be
added to the RST output. A value of 100kΩ is typical for this
application as well. See Figure 2.
Interfacing to Processors with Bidirectional Reset Pins
Some microcontrollers and microprocessors utilize reset
signal pins that are bidirectional in nature, rather than simply
being input only. The Motorola 68HC11 family is one example. To use the MIC2753/4 with these processors, it is
necessary to insert a resistor into the signal path between the
MIC2753/4’s reset output and the microprocessor’s reset
input. This prevents excessive current from flowing due to
contention between the two drivers. The signal present at the
processor’s reset pin will now be of limited drive capability, so
it is necessary to buffer it in order to drive other circuits. This
technique is shown in Figure 3.
At levels of VIN below 1.5V, the MIC2754’s /RST output driver
cannot turn on sufficiently to sink current and produce a valid
logic-low on the /RST output. In this situation, other CMOS
circuits driven by /RST could be allowed to float, causing
Reset Comparator Overdrive
vs. Duration
40
Overvoltage Comparator
Overdrive vs. Duration
8
TA = 25°C
30
DURATION (µs)
DURATION (µs)
7
20
10
1
5
4
3
2
1
TA = 25°C
0
6
10
100
OVERDRIVE (mV)
0
1000
A. Reset
1
10
100
OVERDRIVE (mV)
1000
B. Overvoltage
Figure 1. MIC2753/2754 Transient Immunity Behavior
June 1999
9
MIC2753/2754
MIC2753/2754
Micrel
VCC
Fuse
Microcontroller
MIC2754
Manual
Reset
IN
RST
MR
HV
VCC
GND
10k
2200pF
RST IN
RPULL-DOWN
100k
GND
MCR708A
SCR
MIC94030
22Ω
1k
Figure 2a. MIC2754 Valid Reset Below 1.5V
VCC
Fuse
Manual
Reset
RPULL-UP
100k
MIC2753
IN
RST
MR
HV
Microcontroller
VCC
GND
10k
2200pF
RST IN
MCR708A
SCR
MIC94030
GND
22Ω
1k
Figure 2b. MIC2753 Valid Reset Below 1.5V
BUFFER
/RST signal to
other circuits
VCC
Fuse
Manual
Reset
Microcontroller
MIC2754 RSERIES
4.7k
IN
RST
MR
VCC
GND
RST IN
HV
10k
2200pF
MIC94030
GND
MCR708A
SCR
22Ω
1k
Figure 3. MIC2754 With Processors Using Bidirectional Reset Inputs.
Crowbar Applications
The following MIC275x applications diagrams show an SCR
crowbar circuit. The function of this circuit is to protect system
components from damage caused by excessive supply voltage, as might be generated by a runaway power supply. The
low RDS(on) of the MIC94030 P-channel MOSFET (<1Ω at
VGS = 4.5V) and the 22Ω resistor assure adequate gate
current to trigger the SCR.
The crowbar circuit is designed to be functional over all
operating ranges of the MIC275x. Since the lowest upperthreshold voltage of the MIC275x family is only 3.08V, and
since the SCR-gate forward voltage is about 1V, there is
about 90mA of gate-drive current available: 2.08V ÷ 23Ω =
0.09A. The highest upper-threshold voltage is 5.38V, so
available gate-drive current is about 190mA: 4.38V ÷ 23Ω =
0.190A. The maximum forward gate current of the SCR is
MIC2753/2754
200mA. The SCR trigger characteristics and the gate-drive
capability provide a workable solution for the power-supply
voltage range in question.
The 10kΩ resistor is the pull-up for the open-drain /HV output
of the MIC275x, and the 2200pF capacitor avoids inadvertent
premature triggering of the SCR, which might be caused by
a very narrow spike on the /HV line. Similarly, the 1kΩ resistor
from the SCR-gate to ground keeps the SCR-gate biased off.
The fuse shown in the diagrams, which ultimately protects
both the system components and the crowbar SCR, should
be a fast-blow type. The SCR is rated at 4A(rms), but it can
withstand a brief 25A surge. The crowbar circuit shown
should, conservatively, be capable of blowing a 5A or 6A
fuse.
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June 1999
MIC2753/2754
Micrel
Package Information
1.90 (0.075) REF
0.95 (0.037) REF
1.75 (0.069)
1.50 (0.059)
3.00 (0.118)
2.60 (0.102)
DIMENSIONS:
MM (INCH)
3.02 (0.119)
2.80 (0.110)
0.50 (0.020)
0.35 (0.014)
1.30 (0.051)
0.90 (0.035)
0.20 (0.008)
0.09 (0.004)
10°
0°
0.15 (0.006)
0.00 (0.000)
0.60 (0.024)
0.10 (0.004)
SOT-23-5 (M5)
June 1999
11
MIC2753/2754
MIC2753/2754
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 1999 Micrel Incorporated
MIC2753/2754
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June 1999