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FEATURES
5V or 3.3V power-on reset
True 3V operation power switch
Switches to battery at 3.8V (2.6V for 3.3V
versions)
Excellent for systems designed to operate
with dual power supplies
Asserts resets during power transients
Maintains reset for 350ms after VCC returns to
an in-tolerance condition
Reduces need for discrete components
Precision temperature-compensated voltage
reference and volta ge se ns or
8-pin DIP or space saving 8-pin SO surfac e
mount available
CMOS reset output for low current operation
Operating temperature of -40°C to +85°C
Perfect for PIC microprocessor applications
PIN ASSIGNMENT
DS1836A/C (*DS1836B/D)
PIN DESCRIPTION
VCC - Power Supply Input
VBAT - Battery Supply Input
NC - No Connect
VOUT - Power Supply Output
GND - Ground
IN - Sense Input
NMI - Non-maskable Interrupt
RST (*RST) - Reset Output
DESCRIPTION
The DS1836 MicroManager performs three vital system functions. First, a precision temperature-
compensated reference and comparator circuit monitor the status of the voltage on VCC and when an out-
of-tolerance condition is detected, an internal power-fail signal is generated that forces the reset active. If
VCC continues to degrade, it switches to the battery supply when VCC drops below 3.8V (2.6V for 3.3V
versions). When VCC exceeds 3.9V (2.8V for 3.3V versions); VOUT will again be supplied from VCC.
Reset will remain active for 350 m s after V CC returns to an in-tolerance condition.
Lastly, the DS1836 supports a sense input that sends a non-maskable interrupt whenever the sense input
drops below 1.25V.
DS1836/A/B/C/D
3.3V/5V MicroManage
r
www.maxim-ic.com
8-Pin SO (150mil)
1
2
3
4
8
7
6
5
VCC
VBAT
NC
VOUT
RST(*RST)
NMI
IN
GND
8-Pin DIP (300mil)
VCC
VBAT
NC
VOUT
RST(*RST)
NMI
IN
GND
1
2
3
4
8
7
6
5
DS1836A/B/C/D
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OPERATION
Power Monitor
The DS1836 provides the functions of detecting out-of-tolerance conditions on a 3.3V or 5V power
supply and warning a processor-based system of impending power failure. When VCC is detected as out of
tolerance the RST will be forced active . When VCC returns to a valid state the RST will remain active for
about 350ms and then return to an inactive state until the next VCC out-of-tolerance condition.
On power-up reset is kept active for approximately 350ms after the power supply input has reached the
selected tolerance. This allows the power supply and system power to stabilize before RST is released.
Power Switch (DS1836A & B)
The DS1836 switches the VOUT output between VCC and VBAT. On the initial power-up, VOUT draws
current from the VBAT input until VCC exceeds 3.9V. When VCC exceeds 3.9V VOUT switches from VBAT
to VCC and will not switch back to VBAT until VCC drops below 3.8V. When VCC is below 3.8V, power
will be drawn fr om the supply with the highest voltage: either VCC or VBAT.
Power Switch (DS1836C & D)
The DS1836 switches the VOUT output between VCC and VBAT. On the initial power up, VOUT draws
current from the VBAT input until VCC exceeds 2.8V. When VCC exceeds 2.8V VOUT switches from VBAT
to VCC and will not switch back to VBAT until VCC drops below 2.6V. When VCC is below 2.6V, power
will be drawn fr om the supply with the highest voltage either VCC or VBAT.
BLOCK DIAGRAM Figure 1
* DS1836B and DS1836D
DS1836A/B/C/D
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Non-Maskable Interrupt
The DS1836 generates a non-maskable interrupt (NMI ) for early warning of a power failure. A precision
comparator monitors the voltage level at the IN pin relative to an on-chip reference generated by an
internal band gap. The IN pin is a high impedance input allowing for a user-defined sense point. An
external resistor voltage divider network (Figure 3) is used to interface with high voltage signals. This
sense point may be derived from a regulated supply or from a higher DC voltage level closer to the main
system power input. Since the IN trip point VTP is 1.25V, the proper values for R1 and R2 can be
determined by the equation as shown in Figure 3. Proper operation of the DS1836 requires that the
maximum voltage at the IN pin be limited to the active supply (VCC or VBAT). Therefore, the maximum
allowable voltage at the supply being monitored (VMAX) can also be derived as shown in Figure 3. A
simple approach to solving the equation is to select a value for R2 high enough to keep power
consumption low and solve for R1. The flexibility of the IN input pin allows for detection of power loss
at the earliest point in a power supply system, maximizing the amount of time for system shutdown
between NMI and RST (or RST ).
A pull-up resistor is required for proper operation of the NMI open-drain output. A 10kΩ resistor would
be a typical value for the pull-up resistor.
TYPICAL APPLICATION Figure 2
DS1836A/B/C/D
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NON-MASKABLE INTERRUPT CIRCUIT EXAMPLE Figure 3
V
SENSE = R2R2 R1+ x 1.25
Example: VSENSE = 4.50V at the trip point
100kΩ = R2
Therefore: 4.5 =
100
k
100k R1
+
x 1.25 R1 = 260kΩ
TIMING DIAGRAM: NON-MASKABLE INTERRUPT Figure 4
DS1836A/B/C/D
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OUTPUT VALID CONDITIONS
The DS1836 can maintain valid outputs as long as one input remains above 1.2V. However, the RST
outputs on the DS1836A (or C) use a push-pull output structure which can maintain a valid output below
1.2V on an input. To sink current below 1.2V a resistor can be connected from RST to GND (see Figure
5). This arrangement will maintain a v alid value on the RST outputs even if all supply inputs are at 0V.
During conditions when the RST is in the inactive or high state this arrangement will draw current
through the pull down resistor. A value of about 100 kΩ should be adequate to maintain a valid condition.
The DS1836 NMI output requires a pull-up resistor on the output to maintain a valid output. The value of
the resistor is not critical in most cases but must be set low enough to pull the output to a high state. A
comm on value used is 10kΩs (see Figure 3).
APPLICATION DIAGRAM:
RST VALID TO 0V VCC ON THE DS1836A OR DS1836C Figure 5
TIMING DIAGRAM: POWER-UP Figure 6
DS1836A/B/C/D
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TIMING DIAGRAM: POWER-DOWN Figure 7
TIMING DIAGRAM: POWER SWITCH Figure 8
DS1836A/B/C/D
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ABSOLUTE MAXIMUM RATINGS*
Voltage on VCC or VBAT Pin Relative to Ground -0.5V to +7.0V
Voltage on any I/O Pin Relative to Ground** -0.5V to VOUT + 0.5V
Operating Temperature Range -40°C to +85°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature 260°C for 10 seconds
* This is a stress rating only and functional operation of the device at these or any other conditions above
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for exte nded periods of tim e m ay affect reliability.
**The voltage input on IN can exceed VCC/VBAT if the input current is less than 10mA.
RECOMMENDED DC OPERATING CONDITIONS (-40°C to +85°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Supply Voltage VCC 1.2 5.5 V 1
Secondary Supply Voltage VBAT 1.2 5.5 V 1
DS1836A/B/C/D
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DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC = 1.2V to 5.5V)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Output Voltage @ -500μA VOH V
CC
-0.5
VCC
-0.1
V 1
Input Leakage IIL -1.0 +1.0
μA 2
Output Cur rent @ 2.4V IOH 350
μA 3
Output Cur rent @ 0.4V IOL +10 mA 3
Operating Current @ ∗ 5.5VIN ICC 35 55
μA 4
Operating Current @ ∗ 3.6VIN ICC 30 50
μA 5
Supply Output Current ICC01 100 mA 6
Supply Output Current ICC02 100 mA 7
Supply Output Voltage (VCC) VOUT V
CC
-0.5
VCC
-0.3
V 1, 8
Supply Output Voltage (VBAT) VOUT V
BAT
-0.5
VBAT
-0.3
V 1, 9
RST VCC Trip Point DS1836A(or B)-05 VCCTP 4.50 4.63 4.75 V 1
RST VCC Trip Point DS1836A(or B)-10 VCCTP 4.25 4.37 4.50 V 1
RST VCC Trip Point DS1836C(or D)-10 VCCTP 2.80 2.88 2.97 V 1
RST VCC Trip Point DS1836C(or D)-20 VCCTP 2.67 2.72 2.80 V 1
Power Supply Trip Points (VCC to VBAT)
DS1836 C or D
VCCFTP 2.60 2.65 2.70 V 1, 10
Power Supply Trip Points (VBAT to VCC)
DS1836 C or D
VCCRTP 2.70 2.75 2.80 V 1, 10
VBAT Leakage Current ICC03 0.10
μA 11
Power Supply Trip Points (VCC to VBAT)
DS1836 A or B
VCCFTP 3.80 3.85 3.9 V 1, 10
Power Supply Trip Points (VBAT to VCC)
DS1836 A or B
VCCRTP 3.90 3.95 4.0 V 1, 10
IN Input Trip Point VTP 1.15 1.25 1.35 V 1
Output Capacitance COUT 10 pF
DS1836A/B/C/D
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AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC = 1.2V to 5.5V)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
VTP to NMI Delay tIPD 1
μs
Reset Active Time tRST 200 350 500 ms
VCC Slew Rate (VINTP(MIN) to VINTP(MAX)) tR 0 ns
VCC Detect to RST tRPU 200 350 500 ms 12
VCC Slew Rate (VINTP(MAX) to VINTP(MIN)) tF 300 μs
VCC Detect to RST tRPD 2 10
μs
VCC to VBAT (VCC falling through 2.6V) tFSW 1 μs
VBAT to VCC (VCC rising through 2.8V) tRSW 1 μs
NOTES:
1) All voltages are referenced to ground.
2) Meas ure d w ith outputs open and inputs at VCC or GND.
3) Meas ure d w ith outputs open and VCC or VBAT < 2.7V.
4) Measured with outputs open and both VCC and VBAT < 5.5V.
5) Measured with outputs open and both VCC and VBAT < 3.6V.
6) VOUT = VCC - 0.3V.
7) VOUT = VBAT - 0.3V.
8) VCC < 2.7V.
9) VBAT < 2.0V and VCC < 1.9V.
10) VCCFTP is offset by approximately 0.1V from VCCRTP.
11) VBAT in the off state and VBAT < VCC (VBAT > VCC and VBAT in the off state 1.5μA maximum).
12) tR = 5μs with one supply < 2.5V.
REVISION HISTORY
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