MIC2785
Dual Supply Voltage Monitor
with Manual Reset
General Description
Features
The MIC2785 is a micropower voltage monitor that
•
No external components
provides under-voltage monitoring and manual reset
•
Monitors input voltage for under-voltage condition
capability in a tiny 1.2mm x 1.2mm MLF
®
package. The
•
Separate inputs for supply (VDD) and monitor (VIN)
MIC2785 provides a monitored voltage input (V
IN
) separate
•
+1.5% VIN threshold voltage accuracy
from the supply input (V
DD
). This insures that the reset
•
Valid /RST state with VIN down to 0.0V
(/RST) output maintains a valid output state when the
voltage being monitored ramps up or down. The device
•
Valid /RST state with VDD down to 1.20V
also includes a manual reset input (/MR). The /RST output
•
Factory-programmed 1.62V reference
is an active low push-pull output.
•
Manual reset input (/MR)
The under-voltage detector compares the VIN pin voltage
•
Active low RESET (/RST) output
against the factory-programmed threshold of 1.62V. The
•
Ultra-low input current – 5µA total (VIN and VDD)
reset output is asserted any time the input voltage drops
below the programmed threshold voltage. A reset can be
•
Rejects brief input transients
generated at any time by asserting the manual reset input,
•
-25°C to 85°C operating temperature range
/MR. This reset output will remain active until the release
•
RoHS lead-free compliant
of /MR. The /MR input can also be used to daisy-chain the
•
Available in tiny 6-pin 1.2mm x 1.2mm Thin MLF
®
MIC2785 onto existing power monitoring circuitry or other
package
supervisors. Hysteresis is included to prevent chattering
due to noise.
The MIC2785 consumes a minimum of quiescent current,
Applications
only 5µA, 1.5µA from the main supply pin and 3.5µA from
®
•
Mobile phones
the input pin. Offered in a tiny, space saving 6-pin MLF
•
PDAs
(1.2mm x 1.2mm), package. (RoHS lead-free compliant).
•
GPS receivers
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
___________________________________________________________________________________________________________
Typical Application
Memory or Microprocessor Voltage Monitor
MicroLeadFrame
and MLF are registered trademark of Amkor Technology, 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
March 2009
M9999-031709-A
Micrel, Inc.
MIC2785
Ordering Information
(1)
Part Number
MIC2785-16YFT
Note:
1. Other voltage thresholds available. Contact Micrel for details.
Typical Application
Voltage
1.8V +10%
Nominal Threshold
Voltage
1.62V
Package
6-Pin (1.2mm x 1.2mm) Thin MLF
®
Pin Configuration
6-Pin (1.2mm x 1.2mm) Thin MLF
®
(FL)
Pin Description
Pin Number
1
2
3
4
5
Pin Name
NC
VDD
GND
VIN
/MR
Pin Function
Not Internally Connected.
Analog (Input): Independent supply input for internal circuitry.
Ground.
Analog (Input). Monitored input voltage. An under-voltage condition will trigger a reset
sequence.
Digital (Input): Asserting this pin low initiates an immediate and unconditional reset.
Assuming VIN is above the threshold when /MR is released (returns high), the reset
output will be de-asserted. /MR may be driven by a logic signal or a mechanical switch.
/MR has an internal pull-up to VDD and may be left floating if unused.
Digital (Output): Asserted low whenever the VIN pin voltage falls below the reference
voltage or Manual Reset pin (/MR) is asserted. It will remain asserted until VIN voltage
rises above the threshold voltage and the /MR pin is released. The maximum output
voltage of the /RST pin is VIN. /RST is a push-pull output.
6
/RST
March 2009
2
M9999-031709-A
Micrel, Inc.
MIC2785
Absolute Maximum Ratings
(1)
Supply Voltage (V
DD
)........................................-0.3V to +6V
Monitor Input (V
IN
) ............................................-0.3V to +6V
Input Voltage (V
/MR
) ..........................................-0.3V to +6V
/RST Current .............................................................±20mA
Lead Temperature (soldering, 20sec.)....................... 260°C
Junction Temperature (T
J
) .........................-40°C to +125°C
Storage Temperature (T
s
) ..........................-65°C to +150°C
ESD Rating
(3)
(Human Body Model)
............................. ±1.5kV
Operating Ratings
(2)
Supply Voltage (V
DD
).................................... +1.5V to +5.5V
Monitor Input (V
IN
) ......................................... –0.3V to + V
DD
Input Voltage (V
/MR
) ..................................... –0.3V to + 5.5V
Ambient Temperature (T
A
) .......................... –40°C to +85°C
Junction Thermal Resistance
MLF
®
(θ
JA
).....................................................140.7°C/W
Electrical Characteristics
(4)
V
DD
= 3.1V; V
IN
= V
DD
= 3.1V T
A
= 25°C, bold values indicate –40°C< T
A
< +85°C, unless noted.
Symbol
I
DD
I
IN
V
HYST
t
PROP_TH
V
OL
V
OH
Parameter
Supply Current (V
DD
)
Supply Current (V
IN
)
V
TH
Accuracy
Hysteresis Voltage
Propagation Delay
Output Voltage Low
Output Voltage High
V
IN
= V
TH
±1 .5%, ±100mV
V
IN
≤
V
TH
-1.5%, I
SINK
= 100µA, V
DD
> 1.2V
V
IN
> V
TH
+1.5%, I
SOURCE
= 500µA
0.8 * V
IN
Condition
V
IN
= V
TH
+1.6%, /MR & /RST open
V
IN
= V
TH
+1.6%, /MR & /RST open
-1.5
1.5
5
25
0.3
Min
Typ
1.0
3.5
+1.5
Max
Units
µA
µA
%
%
µs
V
V
/MR Input
V
IH
V
IL
t
PROP_MR
t
MIN
I
PU
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. Specification for packaged product only.
Input High Voltage
Input Low Voltage
Propagation Delay
Minimum Input Pulse Width
Internal Pull-up Current
V
DD
= 3.1V
V
DD
= 3.1V
V
/MR
< (V
IL
–100mV)
V
/MR
< V
IL
reset occurs
1.7
0.4
0.5
33
100
25
V
V
µs
ns
nA
March 2009
3
M9999-031709-A
Micrel, Inc.
MIC2785
Timing Diagram
March 2009
4
M9999-031709-A
Micrel, Inc.
MIC2785
Functional Diagram
Application Information
Design and Product Advantages
The MIC2785’s tiny 1.2mm x 1.2mm Thin MLF
®
package
combined with no external components offers several
advantages compared to conventional voltage
supervisors.
Tremendous savings are captured with decreased board
size, reduced circuit complexity, and decreased bill of
material (BOM) cost.
Power Supply Input (VDD)
The VDD pin provides a stable input power for the
internal circuitry. This insures that the reference circuitry
and monitoring circuitry have a stable voltage over the
entire operating voltage range.
Supply bypassing is not required. However, bypassing
may be valuable depending on the quality of the system
voltage to which the VDD pin is connected. If bypassing
is added, connect the capacitor(s) as closely as possible
to the VDD pin. Place the lowest value capacitors
closest to the VDD pin.
Under-Voltage Detector Input (VIN)
The largest portion of the monitoring circuitry is the VIN
comparator. The VIN pin is connected to the non-
inverting terminal of the comparator. The internal
reference is connected to the inverting terminal of the
comparator. A reset is triggered when VIN falls below
V
REF
. The VIN pin circuitry includes hysteresis to prevent
/RST pin chattering due to noise. The VIN pin is
relatively immune to very brief negative-going transients.
Reset Output (/RST)
The /RST pin is a complementary push-pull output,
which source and sink current. The reset output is
asserted any time the VIN pin voltage is less than the
threshold voltage (V
IN
< V
TH
) or the /MR pin is asserted.
The /RST pin responds very quickly to reset conditions,
typically asserting within 5µs of V
IN
< V
TH
.
The MIC2785 securely monitors the supply voltage of
critical
components
like
microcontrollers
and
microprocessors. With the MIC2785’s /RST pin
connected to the
μP’s
reset pin, the processor will be
properly reset at power on and during power-down and
brown-out conditions.
Manual Reset Input (/MR)
The /MR pin provides the ability to initiate a reset via
external logic or a manual switch. This is in addition to
the MIC2785’s automatic voltage monitoring function.
Asserting the /MR input to a logic low causes an
immediate and unconditional reset. Assuming the VIN
pin voltage is within tolerance when /MR is released
(returns high), the reset output will be de-asserted. /MR
is internally pulled-up to VDD and may be left floating/
open if unused.
March 2009
5
M9999-031709-A
ARM技术
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