MIC2776N-YM5TR [MICROCHIP]
1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5, LEAD FREE, SOT-23, 5 PIN;
| 型号： | MIC2776N-YM5TR |
| 厂家： | 
MICROCHIP |
| 描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5, LEAD FREE, SOT-23, 5 PIN 光电二极管 |
| 文件： | 总8页 (文件大小：158K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC2776
Micro-Power Low Voltage Supervisor
General Description
Features
The MIC2776 is a power supply supervisor which provides
under-voltage monitoring and power-on reset generation in a
compact 5-pin SOTpackage. Features include an adjustable
under-voltage detector, a delay-generator, a manual reset
input, and a choice of active-high, active-low, or open-drain
active-lowresetoutput.Theuser-adjustable monitoringinput
is compared against a 300mV reference. This low reference
voltageallowsmonitoringvoltageslowerthanthosesupported
by previous supervisor ICs.
• User-adjustable input can monitor supplies as low as
0.3V
• ±1.5% threshold accuracy
• Separate V input
DD
• Generates power-on reset pulse (140ms min.)
• Manual reset input
• Choice of active-high, active-low or open-drain active-
low reset output
• Inputs can be pulled above V (7V abs. max.)
DD
• Open-drain output can be pulled above V (7V abs.
The reset output is asserted for no less than 140ms at power-
on and any time the input voltage drops below the reference
voltage. It remains asserted for the timeout period after the
input voltage subsequently rises back above the threshold
boundary. A reset can be generated at any time by asserting
the manual reset input, /MR. The reset output will remain ac-
tive at least 140ms after the release of /MR. The /MR input
can also be used to daisy-chain the MIC2776 onto existing
power monitoring circuitry or other supervisors. Hysteresis
is included to prevent chattering due to noise. Typical supply
current is a low 3.0µA.
DD
max.)
• Ultra-low supply current, 3.0µA typical
• Rejects brief input transients
• IttyBitty™ SOT-23-5 package
Applications
• Monitoring processor, ASIC, or FPGA core voltage
• Computer systems
• PDAs/Hand-held PCs
• Embedded controllers
• Telecommunications systems
• Power supplies
• Wireless / cellular systems
• Networking hardware
Typical Application
MICROPROCESSOR
VCORE 1.0V
VCORE
VI/O
VI/O 2.5V
MIC2776L
R1
R2
/RST
VDD
IN
/RESET GND
Power_Good
/MR
GND
Manual
Reset
IttyBitty™ is a trademark of Micrel, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
November 2005
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MIC2776
MIC2776
Micrel, Inc
Package
Ordering Information
Part Number
Reset Output
Temperature Range
Standard
Marking Pb-Free
Marking
MIC2776N-YM5 UKAA
MIC2776H-YM5 ULAA
MIC2776L-YM5 UMAA
MIC2776N-BM5 UKAA
MIC2776H-BM5 ULAA
MIC2776L-BM5 UMAA
Open-Drain, Active-Low / RST
Active-High, Complementary RST
Active-Low, Complementary /RST
–40ºC to +85ºC
–40ºC to +85ºC
–40ºC to +85ºC
SOT-23-5
SOT-23-5
SOT-23-5
Pin Configuration
/MR GND /RST
/MR GND RST
3
2
1
3
2
1
4
5
4
5
IN
VDD
IN
VDD
SOT-23-5 (M5)
“L” and “N” Version
SOT-23-5 (M5)
“H” Version
Pin Description
Pin Number
Pin Number
Pin Name
RST
Pin Function
MIC2776H
MIC2776L
MIC2776N
1
Digital (Output): Asserted high whenever VIN falls below the reference volt-
age. It will remain asserted for no less than 140ms after VIN returns above
the threshold limit.
1
/RST
Digital (Output): Asserted low whenever VIN falls below the reference volt-
age. It will remain asserted for no less than 140ms after VIN returns above
the threshold limit. (open-drain for “N” version)
2
3
2
3
GND
/MR
Ground
Digital (Input): Driving this pin low initiates an immediate and unconditional
reset. Assuming IN is above the threshold when /MR is released (returns
high), the reset output will be de-asserted no less than 140ms later. /MR
may be driven by a logic signal or a mechanical switch. /MR has an internal
pull-up to VDD and may be left open if unused.
4
5
4
5
IN
Analog (Input): The voltage on this pin is compared to the internal 300mV
reference. An under-voltage condition will trigger a reset sequence.
VDD
Analog (Input): Independent supply input for internal circuitry.
MIC2776
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November 2005
MIC2776
Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (V ).......................................–0.3V to +7V
Supply Voltage (V ) .................................. +1.5V to +5.5V
DD
DD
Input Voltages (V , V ) ...............................–0.3V to +7V
Input Voltages (V , V ) ............................–0.3V to +6.0V
IN
/MR
IN
/MR
RST, (/RST) Current .................................................. 20mA
Output Voltages
V
V
(N version) ......................................–0.3V to +6.0V
Storage Temperature (T ) ........................ –65°C to +150°C
/RST
S
, V
(H and L versions)........ –0.3V to V + 0.3V
/RST RST
DD
ESD Rating, Note 3.................................................... 1.5kV
Ambient Temperature Range (T ) .............. –40°C to +85°C
A
Package Thermal Resistance (θ ).......................256°C/W
JA
Electrical Characteristics
VDD = 3.3V; TA = +25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol
Parameter
Condition
Min
295
Typ
Max
305
10
Units
IDD
Supply Current
VDD = VIN = 3.3V; /MR, RST, /RST open
3.0
µA
IN, UNDER-VOLTAGE DETECTOR INPUT
VREF
VHYST
IIN
Under-Voltage Threshold
Hysteresis Voltage
Input Current
TA = 25°C
300
3
mV
mv
pA
nA
5
TMIN ≤ TA ≤ TMAX
RESET OUTPUTS (/RST, RST)
tPROP
Propagation Delay
VIN = (VREF(MAX) + 100mV) to
VIN = (VREF(MIN) – 100mV)
20
µs
tRST
VOL
Reset Pulse Width
140
280
0.3
ms
V
RST or /RST Output Voltage Low
ISINK = 1.6mA;
V
DD ≥ 1.6V
ISINK = 100µA;
DD ≥ 1.2V, Note 4
ISOURCE = 500µA;
DD ≥ 1.5V
ISOURCE = 10µA;
DD ≥ 1.2V, Note 4
0.3
V
V
V
V
VOH
RST or /RST Output Voltage High
(H and L Version Only)
0.8VDD
0.8VDD
V
V
MANUAL RESET INPUTS (/MR)
VIH
VIL
Input High Voltage
1.5V ≤ VDD ≤ 5.5V
1.5V ≤ VDD ≤ 5.5V
V/MR < VIL
0.7VDD
V
Input Low Voltage
0.3VDD
V
tPROP
tMIN
IPU
Propagation Delay
5
µs
ns
nA
nA
Minimum Input Pulse Width
Internal Pull-Up Current
Input Current, /MR
Reset Occurs, V/MR < VIL
33
100
100
IIN
V/MR < VIL
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. Human body model, 1.5k in series with 100pF.
Note 4. VDD operating range is 1.5V to 5.5V. Output is guaranteed to be asserted down to VDD = 1.2V.
November 2005
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MIC2776
MIC2776
Micrel, Inc
Timing Diagram
VDD
0V
0V
A
VHYST
A
VIN
VREF
>tmin
VOH
VOL
V/MR
VRST
V/RST
tRST
tRST
tRST
VOH
VOL
tRST
VOH
VOL
Propagation delays not shown for clarity.
Note A. The MIC2776 ignores very brief transients.
See “Applications Information” for details.
MIC2776
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November 2005
MIC2776
Micrel, Inc.
Functional Diagram
VDD
IPU
/MR
IN
/RST*
RST*
R
S
Q
One Shot
Delay
/Q
VREF
GND
MIC2776
* Pinout and polarity vary by device type.
See ordering information table.
The reset outputs are asserted any time /MR is asserted or
Functional Description
IN, Under-Voltage Detector Input
if V drops below the threshold voltage. The reset outputs
IN
remain asserted for t
(min) after V subsequently returns
RST
IN
The voltage present at the IN pin is compared to the internal
300mV reference voltage. A reset is triggered if and when
above the threshold boundary and /MR is released. A reset
pulse is also generated at power-on.
V
falls below V
. Typically, a resistor divider is used to
IN
REF
/MR, Manual Reset Input
scale the input voltage to be monitored such that V will fall
IN
The ability to initiate a reset via external logic or a manual
switch is provided in addition to the MIC2776’s automatic
supervisory functions. Driving the /MR input to a logic low
causes an immediate and unconditional reset to occur. As-
below V
as the voltage being monitored falls below the
REF
desired trip-point. Hysteresis is employed to prevent chat-
tering due to noise.
RST, /RST Reset Output
suming V is within tolerance when /MR is released (returns
IN
Typically, the MIC2776 is used to monitor the power supply
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the reset output of a MIC2776 to the
reset input of a µC or µP, the processor will be properly reset
at power-on and during power-down and brown-out condi-
tions. In addition, asserting /MR, the manual reset input, will
activate the reset function.
high), the reset output will be de-asserted no less than t
RST
later. /MR may be driven by a logic signal, or mechanical
switch. Typically, a momentary push-button switch is con-
nected such that /MR is shorted to ground when the switch
contactsclose.Theswitchmaybeconnecteddirectlybetween
/MR and GND. /MR has an internal 100nA pull-up current to
V
and may be left open if unused.
DD
November 2005
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MIC2776
MIC2776
Micrel, Inc
To summarize, the various potential error sources are:
• Variation in V specified at ±1.5%
Application Information
Programming the Voltage Threshold
:
REF
• Resistor tolerance:
Referring to the “Typical Application Circuit”, the voltage
threshold is calculated as follows:
chosen by designer (typically ≤ ±1%)
• Input bias current, I :
IN
R1+R2
(
)
calculated once resistor values are known, typically
very small
V
= V
×
TH
REF
R2
where V
= 0.300V
Taking the various potential error sources into account, the
REF
thresholdvoltagewillbesetslightlybelowtheminimumV
specification of 0.950V so that when the actual threshold
voltage is at its maximum, it will not intrude into the normal
In order to provide the additional criteria needed to solve
for the resistor values, the resistors can be selected such
that the two resistors have a given total value, that is, R1
CORE
operating range of V
be set as follows:
. The target threshold voltage will
+ R2 = R
. Imposing this condition on the resistor val-
CORE
TOTAL
ues provides two equations that can be solved for the two
unknown resistor values. A value such as 1MΩ for R
Given that the total tolerance on V is [V
tolerance] +
REF
TOTAL
TH
is a reasonable choice since it keeps quiescent current to a
generally acceptable level while not causing any measurable
errors due to input bias currents. The larger the resistors, the
[resistor tolerance]
= ±1.5% + ±1% = ±2.5%,
and V
= V
,
TH(max)
CORE(min)
larger the potential errors due to input bias current (I ). The
IN
then V
= V + 2.5% V = 1.025 V
,
maximum recommended value of R
is 3MΩ.
CORE(min)
TH
TH
TH
TOTAL
therefore, solving for V results in
Applying this criteria and rearranging the V expression to
TH
TH
solve for the resistor values gives:
V
0.950
1.025
CORE(min)
V
=
=
= 0.9268V
TH
1.025
R
(
V
REF
)
(
TH
)
TOTAL
R2 =
Solving for R1 and R2 using this value for V and the equa-
tions above yields:
V
TH
R1 = R
– R2
TOTAL
R1 = 676.3kΩ ≈ 673kΩ
R2 = 323.7kΩ ≈ 324kΩ
Application Example
The resulting circuit is shown in Figure 1.
Input Bias Current Effects
Figure1belowillustratesahypotheticalMIC2776application
in which the MIC2776 is used to monitor the core supply of a
Now that the resistor values are known, it is possible to cal-
culate the maximum potential error due to input bias current,
high-performance CPU or DSP. The core supply, V
this example is 1.0V ±5%. The main power rail and I/O volt-
, in
CORE
I . As shown in the “Electrical Characteristics” table, the
age, V , is 2.5V ±5%. As shown in Figure 1, the MIC2776
IN
I/O
maximum value of I is 10nA. (Note that the typical value
is powered by V . The minimum value of V is 2.5V –5%
IN
I/O
I/O
is a much smaller 5pA!) The magnitude of the offset caused
= 2.375V; the maximum is 2.5V +5% = 2.625V. This is well
within the MIC2776’s power supply range of 1.5V to 5.5V.
by I is given by:
IN
V
V
V
V
= I
× (R1||R2) =
-8
Resistors R1 and R2 must be selected to correspond to the
ERROR
ERROR
ERROR
ERROR
IN(max)
5
V
supplyof1.0V.Thegoalistoinsurethatthecoresupply
= ±1 × 10 A × 2.189 ×10 Ω =
CORE
voltage is adequate to insure proper operation, i.e., V
-3
CORE
= ±2.189 × 10 V =
≥ (1.0V –5%) = 0.950V. Because there is always a small
degree of uncertainty due to the accuracy of the resistors,
variationsinthedevices’voltagereference,etc.,thethreshold
will be set slightly below this value. The potential variation in
the MIC2776’s voltage reference is specified as ±1.5%. The
resistors chosen will have their own tolerance specification.
This example will assume the use of 1% accurate resistors.
The potential worst-case error contribution due to input bias
currentcanbecalculatedoncetheresistorvaluesarechosen.
If the guidelines above regarding the maximum total value of
R1+R2 are followed, this error contribution will be very small
thanks to the MIC2776’s very low input bias current.
= ±2.189mV
The typical error is about three orders of magnitude lower
than this - close to one microvolt! Generally, the error
due to input bias can be discounted. If it is to be taken
into account, simply adjust the target threshold voltage
downward by this amount and recalculate R1 and R2. The
resulting value will be very close to optimum. If accuracy
is more important than the quiescent current in the
resistors, simply reduce the value of R
offset errors.
to minimize
TOTAL
MIC2776
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November 2005
MIC2776
Micrel, Inc.
VCORE
1.0V 5%
Ensuring Proper Operation at Low Supply
At levels of V below 1.2V, the MIC2776L’s /RST output
driver cannot turn on sufficiently to produce a valid logic-low
on the /RST output. In this situation, other circuits driven by
/RST could be allowed to float, causing undesired opera-
tion. (In most cases, however, it is expected that the circuits
MICROPROCESSOR
VCORE
VI/O
DD
VI/O
2.5V 5%
R1
MIC2776
676k
1%
/RST
VDD
/RESET GND
IN
R2
324k
1%
driven by the MIC2776L will be similarly inoperative at V
/MR
GND
DD
≤ 1.2V.)
Manual
Reset
If a given application requires that /RST be valid below V
=
DD
1.2V, this can be accomplished by adding a pull-down resis-
tor 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. See Figure 4.
Figure 1. MIC2776 Example Design
Interfacing to Processors With Bidirectional Reset Pins
Some microprocessors have reset signal pins that are bi-
directional, rather than input only. The Motorola 68HC11
family is one example. Because the MIC2776N’s output is
open-drain, it can be connected directly to the processor’s
reset pin using only the pull-up resistor normally required.
See Figure 2.
The statements above also apply to the MIC2776H’s RST
output. That is, to ensure valid RST signal levels at V
<
DD
1.2V, 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 5.
MICROPROCESSOR
VCC
VCC
MICROPROCESSOR
VCC
VCC
MIC2776L
100k
MIC2776N
R1
R2
/RST
VDD
IN
/RESET GND
/RST
VDD
/RESET GND
100k
Rpull-down
R1
R2
IN
/MR
GND
/MR
GND
Manual
Reset
Figure 2. Interfacing to Bidirectional Reset Pin
Transient Response
Figure 4. MIC2776L Valid /Reset Below 1.2V
The MIC2776 is inherently immune to very short negative-
going“glitches.”Verybrieftransientsmayexceedthevoltage
threshold without tripping the output.
MICROPROCESSOR
VCC
VCC
100k
Rpull-up
MIC2776H
AsshowninFigure3,thenarrowerthetransient,thedeeperthe
threshold overdrive that will be ignored by the MIC2776. The
graphrepresentsthetypicalallowabletransientdurationfora
givenamountofthresholdoverdrivethatwillnotgenerateareset.
R1
R2
RST
VDD
IN
RESET GND
/MR
GND
Typical INPUT
Transient Response
Manual
Reset
40
35
30
25
20
15
10
5
Figure 5. MIC2776H Valid Reset Below 1.2V
0
0
100
200
300
RESET COMP. OVERDRIVE, VREF–VIN (mV)
Figure 3. Typical INPUT Transient Response
November 2005
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MIC2776
MIC2776
Micrel, Inc
Package Information
SOT-23-5 (M5)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2000 Micrel, Inc.
MIC2776
8
November 2005
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