DS1836C-10+ ,3.3V/5V MicroManagerapplications V - Power Supply Input CCV - Battery Supply Input BATNC - No Connect V - P ..
DS1842 ,76V, APD, Bias Output Stage with Current MonitoringApplicationsAPD BiasingOrdering InformationGPON Optical Network Unit and Optical LineTransmission P ..
DS1843 ,Fast Sample-and-Hold CircuitApplications Ordering InformationGigabit Passive Optical Network (GPON) OLTPART TEMP RANGE PIN-PACK ..
DS1844 ,Quad Digital PotentiometerElectrical Characteristics table for 5-wire serial communications. Data is loaded MSB first and in ..
DS1844/100 ,Quad Digital Potentiometerblock diagram ofthe DS1844 is shown in Figure 1.SERIAL PORT OPERATIONAs stated, the DS1844 can supp ..
DS1844-010 ,Quad Digital PotentiometerPIN DESCRIPTIONV - 2.7V to 5.5VCCPS - Port SelectA0, A1, A2 - Device Select Pins (2-Wire)SDA - Seri ..
DZ23C36-7-F , 300mW DUAL SURFACE MOUNT ZENER DIODE
DZ23C3V6-7-F , 300mW DUAL SURFACE MOUNT ZENER DIODE
DZ23C3V9-7-F , 300mW DUAL SURFACE MOUNT ZENER DIODE
DZ23C6V2-7-F , 300mW DUAL SURFACE MOUNT ZENER DIODE
DZ23C6V8-7-F , 300mW DUAL SURFACE MOUNT ZENER DIODE
DZ23C8V2 ,Zener DiodesAbsolute Maximum RatingsT = 25
DS1836C-10+
3.3V/5V MicroManager
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 voltage sensor 8-pin DIP or space saving 8-pin SO surface
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 ms after VCC 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 MicroManager
8-Pin SO (150mil)
VCC
VBAT
NC
VOUT
RST(*RST)
NMI
IN
GND
8-Pin DIP (300mil)
VCC
VBAT
NC
VOUT
RST(*RST)
NMI
IN
GND
DS1836A/B/C/D
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 from 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 from the supply with the highest voltage either VCC or VBAT.
BLOCK DIAGRAM Figure 1 * DS1836B and DS1836D
DS1836A/B/C/D
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
NON-MASKABLE INTERRUPT CIRCUIT EXAMPLE Figure 3 VSENSE = R2 R1+ x 1.25
Example: VSENSE = 4.50V at the trip point
100kΩ = R2
Therefore: 4.5 = 100k
100k R1+ x 1.25 R1 = 260kΩ
TIMING DIAGRAM: NON-MASKABLE INTERRUPT Figure 4 DS1836A/B/C/D
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 valid 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 NMIoutput 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
common 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
TIMING DIAGRAM: POWER-DOWN Figure 7
TIMING DIAGRAM: POWER SWITCH Figure 8
