MIC2774H-46BM5TR [MICROCHIP]
Power Supply Support Circuit, Adjustable, 2 Channel, PDSO5, SOT-23, 5 PIN;
| 型号： | MIC2774H-46BM5TR |
| 厂家： | 
MICROCHIP |
| 描述： | Power Supply Support Circuit, Adjustable, 2 Channel, PDSO5, SOT-23, 5 PIN 光电二极管 |
| 文件： | 总8页 (文件大小：730K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Dual Micro-Power Low Voltage Supervisor
General Description
The MIC2774 is a dual power supply supervisor that pro-
vides under-voltage monitoring, manual reset capability, and
power-on reset generation in a compact 5-pin SOT package.
Features include two under-voltage detectors, one fixed and
one adjustable, and a choice of reset outputs. One under-
• Monitors two independent power supplies for under-volt-
age conditions
• One fixed and one user adjustable input
• Choice of factory-programmed thresholds
• Adjustable input can monitor supplies as low as 0.3V
• Generates 140ms (minimum) power-on reset pulse
• Manual reset input
voltagedetectorcomparesV againstafixedthreshold.Ten
DD
factory-programmed thresholds are available. The second,
user-adjustableinputiscomparedagainsta300mVreference.
This low reference voltage allows monitoring voltages lower
than those supported by previous supervisor ICs.
• Choice of active-high, active-low, or open-drain active-
low reset outputs
• Inputs may be pulled above V (7V abs. max.)
DD
• Open-drain output can be pulled above V (7V abs
The reset outputs are asserted at power-on and any time
either voltage drops below the programmed threshold volt-
ages and remains asserted for 140ms (min.) after they
subsequently rise back above the threshold boundaries.
Manual reset functionality can be provided by a switch con-
nected between ground and the /MR input. A wide choice of
voltage thresholds provides for a variety of supply voltages
and tolerances. Hysteresis is included to prevent chattering
due to noise. Typical supply current is a low 3.5µA.
DD
max.)
• /RST output valid down to 1.2V
• Ultra-low supply current, 3.5µA typical
• Rejects brief input transients
• IttyBitty™ 5-lead SOT-23 package
• Pin compatible upgrade for MAX6306/09/12
Applications
• Monitoring processor ASIC, or FAGA core and I/O volt-
ages
• PDAs, hand-held PCs
• Embedded controllers
• Telecommunications systems
• Power supplies
• Wireless / Cellular systems
• Networking hardware
Ordering Information
Part Number
Reset Output
Temperature
Range
Package
Standard
Marking Pb-Free
Marking
MIC2774N-XXBM5 UGXX(1) MIC2774N-XXYM5
MIC2774H-XXBM5 UHXX(1) MIC2774H-XXYM5
UGXX(1)
Open-Drain. Active-Low (/RST)
-40°C to +85°C SOT-23-5
UHXX(1) Active-High. Complementary (RST) -40°C to +85°C SOT-23-5
UIXX(1)
Active-Low. Complementary (/RST) -40°C to +85°C SOT-23-5
MIC2774L-XXBM5 UIXX(1)
MIC2774L-XXYM5
Notes:
1.
XX = Voltage options, see table on page 2. Underscore indicates a Pb-Free part.
Typical Application
MICROPROCESSOR
VCORE 1.0V
VI/O 2.5V
VCORE
VI/O
MIC2774L-23
R1
R2
IN
/RESET
GND
Power_Good
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
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Standard Voltage Options*
Voltage
Code
Typical
Application (VDD
Nominal Threshold
)
Voltage (VTH
)
46
44
31
29
28
26
25
23
22
17
5.0V ±5%
5.0V ±10%
3.3V ±5%
3.3V ±10%
3.0V ±5%
2.85V ±5%
2.70V ±5%
2.5V ±5%
2.4V ±5%
1.8V ±5%
4.68
4.43
3.09
2.93
2.81
2.67
2.53
2.34
2.25
1.69
*There are ten standard versions available with an order increment of 3000 pieces. Samples of standard versions are
normally available from stock. Contact factory for information on non-standard versions. Available in tape-and-reel only.
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)
“H” Version
SOT-23-5 (M5)
“L” and “N” Version
Pin Description
Pin Number
Pin Number
Pin Name
RST
Pin Function
MIC2774H
MIC2774L
MIC2774N
1
Digital (Output): Asserted high whenever VIN or VDD falls below the threshold
voltage. It will remain asserted for no less than 140ms after VIN and VDD
return above the threshold limits.
1
/RST
Digital (Output): Asserted low whenever VIN or VDD falls below the threshold
voltage. It will remain asserted for no less than 140ms after VIN and VDD
return above the threshold limits. (open-drain for “N” version)
2
3
2
3
GND
/MR
Ground
Digital (Input): Driving this pin low initiates immediate and unconditional re-
set. Assuming VIN and VDD are above the thresholds 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): Power supply input for internal circuitry and input to the fixed
voltage monitor. The voltage on this pin is compared against the internal
reference. An undervoltage condition will trigger a reset sequence.
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Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (V
)
–0.3V to +7V
–0.3V to +7V
–0.3V to +7V
20mA
Supply Voltage (V
)
+1.5V to +5.5V
–0.3V to +6.0V
DD
DD
Input Voltages (V , V
)
Input Voltages (V , V
)
IN
/MR
IN
/MR
Output Voltages (V
, V
)
Output Voltages
/RST RST
V
V
(N version),
–0.3V to +6.0V
RST, (/RST) Current
/RST
, V
(H and L versions)
–0.3V to V +0.3V
/RST RST
DD
Storage Temperature (T )
–65°C to +150°C
1.5kV
S
Ambient Temperature Range (T )
–40°C to +85°C
256°C/W
A
ESD Rating, Note 3
Package Thermal Resistance (θ )
JA
Note 5; T= +25°C, bold values indicate –40°C ≤ T≤ +85°C; unless noted
Symbol
Parameter
Condition
Min
Typ
Max
Units
IDD
Supply Current
VDD = VIN = VTH +1.6%,
Note 5; /MR, RST, /RST open
3.5
µA
VDD VOLTAGE THRESHOLD
Under-Voltage Threshold On VDD
TH–1.5% VTH
V
(See Standard Voltage Options Table)
VHYST
Hysteresis Voltage
1
%
IN, UNDER-VOLTAGE DETECTOR INPUT
VREF
VHYST
IIN
Under-Voltage Threshold
Hysteresis Voltage
Input Current
Note 5
295
300
3
305
10
mV
mV
5
pA
nA
TMIN ≤ TA ≤ TMAX
RST, /RST OUTPUTS
tPROP
Propagation Delay
VIN = (VREF(MAX) + 100mV) to
VIN = (VREF(MIN) – 100mV), /MR = open;
20
µs
tRST
Reset Pulse Width
TMIN ≤ TA ≤ TMAX
140
280
0.3
ms
V
VOL
RST or /RST Output Voltage Low
ISINK = 1.6mA;
VDD ≥ 1.6V
ISINK = 100µA;
VDD ≥ 1.2V; Note 4
0.3
V
V
V
VOH
RST or /RST Output Voltage High
(H and L Version Only)
ISOURCE = 500µA;
VDD ≥ 1.5V
0.8VDD
0.8VDD
ISOURCE = 10µA;
VDD ≥ 1.2V; Note 4
/MR INPUTS
VIH
VIL
Input High Voltage
Note 5
0.7VDD
V
Input Low Voltage
Note 5
0.3VDD
V
tPROP
tMIN
IPU
Propagation Delay
V/MR < (VIL –100mV); Note 5
Reset Occurs, V/MR < V
VIM = 0V
5
µs
ns
nA
nA
Minimum Input Pulse Width
Internal Pull-up Current
Input Current, /MR
33
100
100
250
250
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.
Note 5. VDD equals nominal “Typical Application (VDD)” as shown in “Standard Voltage Options Table.”
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Timing Diagram
DD
0V
HYST
TH
A
A
A
IN
0V
HYST
REF
> tMIN
IH
IL
/MR
tRST
tRST
tRST
OH
/RST
(ACTIVE LOW) OL
OH
RST
(ACTIVE HIGH) OL
Propagation delays not shown for clarity.
Note A. The MIC2774 ignores very brief transients.
See “Applications Information” for details.
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Functional Diagram
DD
/RST*
RST*
VREF
IN
Delay
VDD
IPU
VREF
/MR
MIC2774
GND
* Pinout andpolarity vary by device type
See ordering information table
MIC2774 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 conditions. In addition, asserting /MR, the manual
reset input, will activate the reset function.
Functional Description
IN, Under-Voltage Detector Input
The voltage present at the IN pin is compared to the internal
300mV reference voltage.Areset is triggered if and when V
IN
The reset output is asserted any time /MR is asserted or if V
IN
falls below V
. Typically, a resistor divider is used to scale
REF
orV dropsbelowthecorrespondingthresholdvoltage.The
DD
the input voltage to be monitored such that V will fall below
IN
reset output remains asserted for t
(min) after V and/or
RST
IN
V
as the voltage being monitored falls below the desired
REF
V
subsequently return above the threshold boundaries
DD
trip-point. Hysteresis is employed to prevent chattering due
to noise. The comparator on the IN pin is relatively immune
to very brief negative-going transients.
and/or /MR is released. A reset pulse is also generated at
power-on.Hysteresisisincludedinthecomparatorstoprevent
chattering of the output due to noise.
V
Input
DD
/MR, Manual Reset Input
TheV pinisboththepowersupplyterminalandamonitored
DD
The ability to initiate a reset via external logic or a manual
switch is provided in addition to the MIC2774’s automatic
supervisory functions. Driving the /MR input to a logic low
causes an immediate and unconditional reset to occur.
input voltage. The voltage at this pin is continually compared
against the internal reference. The trip-point at which a reset
occurs is factory programmed. A reset is triggered if and
when V falls below the trip-point. Hysteresis is employed
DD
Assuming V and V
are within tolerance when /MR is
IN
DD
to prevent chattering due to noise. The comparator on the
released (returns high), the reset output will be de-asserted
no less than t later. /MR may be driven by a logic signal,
V
input is relatively immune to very brief negative-going
DD
RST
transients.
or mechanical switch. Typically, a momentary push-button
switch is connected such that /MR is shorted to ground when
the switch contacts close. Switch de-bouncing is performed
internally; the switch may be connected directly between
RST, /RST Reset Output
Typically, the MIC2774 is used to monitor the power supplies
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the appropriate reset output of a
/MR and GND. /MR is internally pulled-up to V and may
DD
be left open if unused.
October 2005
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Micrel
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 on the IN pin is calculated as follows:
chosen by designer (typically ≤ ±1%)
• Input bias current, I :
IN
R1 +R2
= 0.300V
calculated once resistor values are known, typically
very small
V
where V
REF
Taking the various potential error sources into account, the
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
thresholdvoltagewillbesetslightlybelowtheminimumV
CORE
specification of 0.950V so that when the actual threshold
voltage is at its maximum, it will not intrude into the normal
+ R2 = R
. Imposing this condition on the resistor val-
TOTAL
operating range of V
be set as follows:
. The target threshold voltage will
CORE
ues provides two equations that can be solved for the two
unknown resistor values. A value such as 1MΩ for R
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
TOTAL
Given that the total tolerance on V for the IN pin is [V
REF
TH
tolerance] + [resistor tolerance]
= ±1.5% + ±1% = ±2.5%,
larger the potential errors due to input bias current (I ). The
and V
= V
CORE(min)
IN
TH(max)
maximum recommended value of R
is 3MΩ.
then V
= V + 2.5% V = 1.025 V
TH TH TH
CORE(min)
Applying this criteria and rearranging the V expression to
TH
therefore, solving for V results in
TH
solve for the resistor values gives:
V
0.950
1.025
CORE(min)
V
=
= 0.9268V
REF
TOTAL
1.025
R2
Solving for R1 and R2 using this value for V and the equa-
tions above yields:
TH
TOTAL
R1 = 676.3kΩ 673kΩ
R2 = 323.7kΩ 324kΩ
Application Example
The resulting circuit is shown in Figure 1.
Input Bias Current Effects
Figure 1 below illustrates a hypothetical MIC2774L-23 ap-
plication in which the MIC2774L-23 is used to monitor the
core and I/O supplies of a high-performance CPU or DSP.
Now that the resistor values are known, it is possible to cal-
culate the maximum potential error due to input bias current,
The core supply, V
, in the example is 1.0V ±5%. The
CORE
main power rail and I/O voltage, V , is 2.5V ±5%. As shown
I . As shown in the “Electrical Characteristics” table, the
I/O
IN
in Figure 1, the MIC2774 is powered by V . The minimum
maximum value of I is 10nA. (Note that the typical value
I/O
IN
value of V is 2.5V –5% = 2.375V; the maximum is 2.5V
is a much smaller 5pA!) The magnitude of the offset caused
I/O
+5% = 2.625V. This is well within the device’s supply range
of 1.5V to 5.5V.
by I is given by:
IN
ERROR
Resistors R1 and R2 must be selected to correspond to the
5
V
supply of 1.0V. The goal is to insure that the core
2.189 10
CORE
ERROR
ERROR
supply voltage is adequate to insure proper operation, i.e.,
≥ (1.0V –5%) = 0.950V. Because there is always
3
V
V
CORE
a small degree of uncertainty due to the accuracy of the
resistors, variations in the devices’ voltage reference, etc.,
the threshold will be set slightly below this value. The po-
2.189mV
ERROR
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
tential variation in the MIC2774’s voltage reference (V
)
REF
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 er-
ror contribution due to input bias current can be calculated
once the resistor values are chosen. If the guidelines above
regardingthemaximumtotalvalueofR1+R2arefollowed,this
error contribution will be very small thanks to the MIC2774’s
very low input bias current.
resistors, simply reduce the value of R
offset errors.
to minimize
M9999-102605
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October 2005
MIC2774
Micrel
Typical V
DD
VCORE
1.0V 5%
Trans ient R es pons e
MICROPROCESSOR
100
80
60
40
20
0
VCORE
VI/O
VI/O
2.5V 5%
R1
MIC2774L-23
676k
1%
IN
/RESET
GND
R2
324k
1%
Manual
Reset
0
500
1000
1500
2000
RESET COMP. OVERDRIVE, VREF –V DD(mV)
Figure 1. MIC2774 Example Design
Figure 3b. Typical V Transient Response
DD
Interfacing to Processors With Bidirectional Reset Pins
Ensuring Proper Operation at Low Supply
Some microprocessors have reset signal pins that are bi-
directional, rather than input only. The Motorola 68HC11
family is one example. Because the MIC2774N’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.
At levels of V below 1.2V, the MIC2774’s reset output can-
DD
not turn on sufficiently to produce a valid logic-low on /RST.
In this situation, circuits driven by /RST could be allowed to
float, causing undesired operation. (In most cases, however,
it is expected that the circuits driven by the MIC2774L will be
similarly inoperative at V ≤ 1.2V.)
DD
If a given application requires that /RST be valid below V
MICROPROCESSOR
VCC
DD
= 1.2V, this can be accomplished by adding a pull-down re-
sistor to the /RST output. A value of 100kΩ is recommended
as this is usually an acceptable compromise of quiescent
current and pull-down current. The resistor’s value is not
critical, however. See Figure 4.
VCC
100k
MIC2774N-XX
/RST
/RESET
GND
R1
R2
IN
The statements above also apply to the MIC2774H’s RST
/MR
GND
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.
Figure 2. Interfacing to Bidirectional Reset Pin
Transient response
MICROPROCESSOR
VCC
VCC
The MIC2774 is inherently immune to very short negative-
going“glitches.”Verybrieftransientsmayexceedthevoltage
thresholds without tripping the output.
MIC2774L-XX
R1
R2
/RST
IN
/RESET
GND
As shown in Figure 3a and 3b, in general the narrower the
transient, the deeper the threshold overdrive that will be
ignored by the MIC2774. The graphs represent the typical
allowable transient duration for a given amount of threshold
overdrive that will not generate a reset.
100k
Rpull-down
Manual
Reset
Typical IN
Trans ient R es pons e
40
35
30
25
20
15
10
5
Figure 4. MIC2774L Valid /RST Below 1.2V
MICROPROCESSOR
VCC
VCC
100k
Rpull-up
MIC2774H-XX
R1
R2
RST
IN
RESET
GND
0
0
100
200
300
RESET COMP. OVERDRIVE, VREF –V IN (mV)
Figure 3a. Typical INPUT Transient Response
Manual
Reset
Figure 5. MIC2774H Valid RST Below 1.2V
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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.
© 2004 Micrel Incorporated
M9999-102605
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