■ Precision Voltage Monitor:
SP690A/SP802L/SP805L at 4.65V
SP692A/SP802M/SP805M at 4.40V
■ Reset Time Delay - 200ms
■ Watchdog Timer - 1.6 sec timeout
■ Minimum component count
■ 60µA Maximum Operating Supply Current
■ 0.6µA Maximum Battery Backup Current
■ 0.1µA Maximum Battery Standby Current
■ Power Switching
250mA Output in VCC Mode (0.6Ω)
25mA Output in Battery Mode (5Ω)
■ Voltage Monitor for Power Fail or
Low Battery Warning
■ Available in 8 pin SO and DIP packages
■ RESET asserted down to V
■ Pin Compatible Upgrades to
MAX690A/692A/802L/802M/805L
CC
= 1V
SP690A/692A/802L/
802M/805L/805M
DESCRIPTION
The SP690A/692A/802L/802M/805L/805M are a family of microprocessor (µP) supervisory
circuits that integrate a myriad of components involved in discrete solutions to monitor powersupply and battery-control functions in µP and digital systems. The series will significantly
improve system reliability and operational efficiency when compared to discrete solutions.
The features of the SP690A/692A/802L/802M/805L/805M include a watchdog timer, a µP
reset and backup-battery switchover, and power-failure warning, a complete µP monitoring
and watchdog solution. The series is ideal for applications in automotive systems, computers,
controllers, and intelligent instruments. All designs where it is critical to monitor the power
supply to the µP and it’s related digital components will find the series to be an ideal solution.
These are stress ratings only and functional operation
of the device at these ratings or any other above those
indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time
may affect reliability and cause permanent damage to
the device.
VCC........................................................-0.3V to 6.0V
V
.....................................................-0.3V to 6.0V
BATT
All Other Inputs (NOTE 1)..................-0.3V to (VCC to 0.3V)
Vcc=4.75v to 5.50V for SP690A/SP802L/SP805L, VCC=4.50V to 5.50V for SP692A/SP802M/SP805M, V
unless otherwise noted.
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NOTE 1: The input voltage limits on PFI (pin 4) and WDI (pin 6) may be exceeded if the current into
these pins is limited to less than 10 mA.
NOTE 2: Either VCC or V
can go to 0V if the other is greater than 2.0V.
BATT
NOTE 3: "-" equals the battery-charging current, "+" equals the battery-discharging current.
NOTE 4: WDI is guaranteed to be in an intermediate, non-logic level state if WDI is floating and V
is in the operating voltage range. WDI is internally biased to 35% of VCC with an input impedance of
50KΩ.
NOTE 5: SP690A, SP692A, SP802L, and SP802M only.
NOTE 6: SP805L and SP805M only.
old. When VCC falls below V
VCC is below the reset threshold, V
connects to V
capacitor from V
. Connect a 0.1µF
BATT
to GND.
OUT
BATT
OUT
and
OUT
Pin 2 — VCC — +5V Supply Input
Pin3 — GND — Ground reference for all signals
Pin 4 — PFI — Power-Fail Input. This is the
noninverting input to the power-fail comparator. When PFI is less than 1.25V,
PFO goes low. Connect PFI to GND or
V
when not used.
OUT
Pin 5 — PFO — Power-Fail Output.
Pin 6 — WDI — Watchdog Input. WDI is a
three level input. If WDI remains high or
low for 1.6sec, the internal watchdog timer
triggers a reset. If WDI is left floating or
connected to a high-impedance tri-state
buffer, the watchdog feature is disabled.
The internal watchdog timer clears whenever reset is asserted.
0.8V
PFI
1.25V
Figure 11. Internal Block Diagram
*( ) SP805 only
PFO
Pin 7 for SP805 only — RESET (Active High)–
Reset Output is the inverse of RESET;
when RESET is asserted, the RESET
output voltage = VCC or V
whichever is higher.
Pin 8 — V
VCC falls below the reset threshold, V
will be switched to V
20mV greater than VCC. When VCC rises
20mV above V
reconnected to VCC. The 40mV
— Backup-Battery Input. When
BATT
OUT
, V
BATT
if V
will be
OUT
BATT
BATT
BATT
is
hysteresis prevents repeated switching if
VCC falls slowly.
,
Pin 7 for SP690A/692A/802 only — RESET
(Active Low)– Reset Output. RESET Output goes low whenever VCC falls below
the reset threshold or whenever WDI
remains high or low longer than 1.6
seconds. RESET remains low for 200ms
after VCC crosses the reset threshold
voltage on power-up or after being triggered by WDI.
The SP690A/692A/802L/802M/805L/805M
provide four key functions:
1. A battery backup switching for CMOS RAM,
CMOS microprocessors, or other logic.
2. A reset output during power-up, power-down
and brownout conditions.
3. A reset pulse if the optional watchdog timer
has not been toggled within a specified time.
4. A 1.25V threshold detector for power-fail
warning, low battery detection, or to monitor a
power supply other than +5V.
The parts differ in their reset-voltage threshold
levels and reset outputs. The SP690A/802L/805L generate a reset when the supply voltage
drops below 4.65V. The SP692A/802M/805M
generate a reset below 4.40V.
The SP690A/692A/802L/802M/805L/805M
are ideally suited for applications in automotive
systems, intelligent instruments, and batterypowered computers and controllers. All designs
into an environment where it is critical to
monitor the power supply to the µP and it’s
related digital components will find the
SSP690A/692A/802L/802M/805L/805M ideal.
Regulated +5V
CC
V
RESET
µP
NMI
I/O LINE
GND
BUS
RAM
V
GND
CMOS
Figure 12. Typical Operating Circuit
0.1µF
RESET
PFO
WDI
OUT
V
CC
Unregulated
CC
V
GND
PFI
V
BATT
DC
3.6V
Lithium
Battery
R
1
R
2
The SP690A/692A/802L/802M/805L/805M
microprocessor (µP) supervisory circuits
monitor the power supplied to digital circuits
such as microprocessors, microcontrollers, or
memory. The series is an ideal solution for
portable, battery-powered equipment that
requires power supply monitoring. Implementing
this series will reduce the number of
components and overall complexity. The
watchdog functions of this product family will
continuously oversee the operational status of a
system. The operational features and benefits of
the SP690A/692A/802L/802M/805L/805M are
described in more detail below.
Reset Output
The microprocessor's (µP's) reset input starts
the µP in a known state. When the µP is in an
unknown state, it should be held in reset. The
SP690A/SP692A/SP802 assert reset during
power-up and prevent code execution errors
during power-down or brownout conditions.
On power-up, once VCC reaches 1V, RESET is
guaranteed to be a logic low. As VCC rises,
RESET remains low. When VCC exceeds the
reset threshold, RESET will remain low for
200ms, Figure 9. If a brownout condition
occurs and VCC dips below the reset threshold,
RESET is triggered. Each time RESET is
triggered, it stays low for the reset pulse width
interval. If a brownout condition interrupts a
previously initiated reset pulse, the reset pulse
continues for another 200ms. On power-down,
once VCC goes below the threshold, RESET is
guaranteed to be logic low until VCC drops
below 1V.
RESET is also triggered by a watchdog timeout.
If WDI remains either high or low for a period
that exceeds the watchdog timeout period (1.6
sec), RESET pulses low for 200mS. As long as
RESET is asserted, the watchdog timer remains
clear. When RESET comes high, the watchdog
resumes timing and must be serviced within
1.6sec. If WDI is tied high or low, a RESET
pulse is triggered every 1.8sec (tWD plus tRS).
The SP805L/M active-high RESET output is
the inverse of the SP690A/SP692A/SP802 RESET output, and is valid with VCC down to 1V.
Some µP's, such as Intel's 80C51, require an
active-high reset pulse.
Watchdog Input
The watchdog circuit monitors the µP's activity.
If the µP does not toggle the watchdog input
(WDI) within 1.6sec, a reset pulse is triggered.
The internal 1.6sec timer is cleared by either a
reset pulse or by floating the WDI input. As long
as RESET is asserted or the WDI input is
floating, the timer remains cleared and does not
count. As soon as RESET is released and WDI
is driven high or low, the timer starts counting.
It can detect pulses as short as 50ns.
Power-Fail Comparator
The Power-Fail Comparator can be used as an
under-voltage detector to signal the failing of a
power supply (it is completely separate from the
rest of the circuitry and does not need to be
dedicated to this function). The PFI input is
compared to an internal 1.25V reference. If PFI
is less than 1.25V, PFO goes low. The external
voltage divider drives PFI to sense the
unregulated DC input to the +5V regulator. The
voltage-divider ratio can be chosen such that the
voltage at PFI falls below 1.25V just before the
+5V regulator drops out. PFO then triggers an
interrupt which signals the µP to prepare for
power-down.
When V
comparator is turned off and PFO is forced low
connects to V
BATT
, the power-fail
OUT
to conserve backup-battery power.
Backup-Battery Switchover
V
SW1
V
OUT
BATT
D1
V
D3
CC
D2
SW2
GND
NOITIDNOC1WS2WS
V
CC
V
CC
V>
V
CC
TTAB
V
CC
V<
V
CC
TTAB
Reset Threshold = 4.65V in SP690A/802L/805L
Reset Threshold = 4.40V in SP692A/802M/805M
In the event of a brownout or power failure, it
may be necessary to preserve the contents of
RAM. With a backup battery installed at V
the RAM is assured to have power if VCC fails.
BATT
As long as VCC exceeds the reset threshold,
V
connects to VCC through a 0.6Ω PMOS
OUT
power switch. Once VCC falls below the reset
threshold, VCC or V
switches to V
through a 5Ω switch only when VCC is below the
OUT
reset threshold and V
, whichever is higher,
BATT
. V
connects to V
BATT
is greater than VCC.
BATT
OUT
When VCC exceeds the reset threshold, it is
connected to V
applied to V
the diode (D1) between V
conduct current from V
more than .6V above V
When V
activated and the internal circuitry will be pow-
BATT
, regardless of the voltage
OUT
Figure 13. During this time,
BATT
BATT
OUT
connects to V
and V
BATT
to V
.
OUT
if V
OUT
, backup mode is
OUT
will
BATT
is
ered from the battery Figure 14. When VCC is
just below V
current drawn from V
30µA. When VCC drops to more than 1V below
V
, the internal switchover comparator shuts
BATT
off and the supply current falls to less than 0.6µA.
Figure 16. Backup Power Source Using High Capacity
Capacitor with SP690A/802L/805L and a +5V ±5% Supply
+5V
VCC
GND
VOUT
CONNECT TO
STATIC RAM
RESET
(RESET)*
*( ) SP805L only
CONNECT
TO µP
TESER)ylno508PS(hgihcigoL
IDWdelbasidsiremitgodhctaW
Figure 14. Input and Output Status in Battery-Backup Mode.
To enter the Battery-Backup mode, VCC must be less than the
Reset threshold and less than V
BATT
.
Using a High Capacity Capacitor
as a Backup Power Source
VBATT has the same operating voltage range as
VCC, and the battery-switchover threshold voltages are typically +20mV centered at VBATT,
allowing use of a capacitor and a simple charging
circuit as a backup source (see Figure 16).
TRAP
REBMUNREBMUN
REBMUNREBMUN
REBMUN
MUMIXAM
YRETTAB-PUKCABYRETTAB-PUKCAB
YRETTAB-PUKCABYRETTAB-PUKCAB
YRETTAB-PUKCAB
]V[EGATLOV]V[EGATLOV
]V[EGATLOV]V[EGATLOV
]V[EGATLOV
A096PS
L208PS
08.4
L508PS
A296PS
M208PS
55.4
M508PS
If VCC is above the reset threshold and VBATT
is 0.5V above VCC, current flows to VOUT and
VCC from VBATT until the voltage at VBATT is
less than 0.5V above VCC.
Leakage current through the capacitor charging
diode and the SP690A/SP802L/SP805L internal
power diode eventually discharges the capacitor
to VCC. Also, if VCC and VBATT start from 0.5V
above the reset threshold and power is lost at
VCC, the capacitor on VBA TT dischar ges through
VCC until VBA TT reaches the reset threshold; the
SP690A/SP802L/SP805L then switches to
battery-backup mode.
Figure 17. Backup Power Source Using High Capacity
Capacitor with SP692A/802M/805M and a +5V ±10% Supply
11
Page 12
+5V
PFO
V
CC
GND
PFI
PFO
1.25
R
2
V
TRIP
=
VH =
R
=
L
- 1.25
V
R
R1 + R2 || R
3
connect to µP
1.25
R
2
R1 + R
+
1
1.25
2
|| R
R
V
IN
*C
1
*optional
2
5.0 - 1.25
3
R
3
3
Operation Without a Backup Power
Source
R
1
R
2
If a backup power source is not used, ground
V
and connect V
BATT
no need to switch over to any backup power
source, V
direct connection to VCC eliminates any voltage
does not need to be switched. A
OUT
drops across the switch which may push V
below VCC.
to VCC. Since there is
OUT
OUT
Replacing the Backup Battery
The backup battery can be removed while V
remains valid, without danger of triggering
CC
RESET/RESET. As long as VCC stays above the
reset threshold, battery-backup mode cannot be
entered.
Adding Hysteresis to the Power-Fail
Comparator
+5V
0V
0V
Figure 18. Adding Hysteresis to the POWER-FAIL
Comparator
V
L
V
TRIP
V
H
V
IN
Allowable Backup Power-Source
Batteries
Lithium batteries work very well as backup
batteries due to very low self-discharge rate and
high energy density. Single lithium batteries
with open-circuit voltages of 3.0V to 3.6V are
ideal. Any battery with an open-circuit voltage
less than the minimum reset threshold plus 0.3V
can be connected directly to the V
this series with no additional circuitry; see
BATT
input of
FIGURE 12. However, batteries with opencircuit voltages that are greater than this value
cannot be used for backup, as current is sourced
into V
when VCC is close to the reset threshold.
through the diode (D1 in Figure 13)
OUT
Hysteresis adds a noise margin to the power-fail
comparator and prevents repeated triggering of
PFO when VIN is close to its trip point. Figure 18
shows how to add hysteresis to the power-fail
comparator. Select the ratio of R1 and R2 such
that PFI sees 1.25V when VIN falls to its trip
point (V
typically be an order of magnitude greater (about
). R3 adds the hysteresis. It will
TRIP
10 times) than R1 or R2. The current through R
and R2 should be at least 1µA to ensure that the
25nA (max) PFI input current does not shift the
trip point. R3 should be larger than 10KΩ so it
does not load down the PFO pin. Capacitor C1
adds additional noise rejection.
Monitoring a Negative Voltage
The power-fail comparator can be used to monitor
a negative supply rail using the circuit of Figure
19. When the negative rail is valid, PFO is low.
When the negative supply voltage drops, PFO
goes high. This circuit's accuracy is
affected by the PFI threshold tolerance, the V
voltage, and the resistors, R1 and R2.
Interfacing to Microprocessors with
Bidirectional Reset Pins
Microprocessors with bidirectional reset pins,
such as the Motorola 68HC11 series, can contend with this series' RESET output. If, for
example, the RESET output is driven high and
the µP wants to pull it low, indeterminate logic
levels may result. To correct this, connect a
4.7KΩ resistor between the RESET output and
the µP reset I/O, as in Figure 20. Buffer the
RESET output to other system components.
GND
Figure 20. Interfacing to Microprocessors with
Bidirectional RESET I/O
SP690ACN..........................................................0°C to +70°C....................................................8-Pin NSOIC
SP690ACP........................................................0°C to +70°C.........................................................8-Pin PDIP
SP690AEN......................................................-40°C to +85°C.....................................................8-Pin NSOIC
SP690AEP.......................................................-40°C to +85°C.......................................................8-Pin PDIP
SP692ACN........................................................0°C to +70°C......................................................8-Pin NSOIC
SP692ACP........................................................0°C to +70°C.........................................................8-Pin PDIP
SP692AEN......................................................-40°C to +85°C.....................................................8-Pin NSOIC
SP692AEP.......................................................-40°C to +85°C.......................................................8-Pin PDIP
SP802LCN........................................................0°C to +70°C......................................................8-Pin NSOIC
SP802LCP........................................................0°C to +70°C.........................................................8-Pin PDIP
SP802LEN.......................................................-40°C to +85°C....................................................8-Pin NSOIC
SP802LEP.......................................................-40°C to +85°C.......................................................8-Pin PDIP
SP802MCN.......................................................0°C to +70°C......................................................8-Pin NSOIC
SP802MCP.......................................................0°C to +70°C.........................................................8-Pin PDIP
SP802MEN......................................................-40°C to +85°C....................................................8-Pin NSOIC
SP802MEP......................................................-40°C to +85°C.......................................................8-Pin PDIP
SP805LCN........................................................0°C to +70°C......................................................8-Pin NSOIC
SP805LCP........................................................0°C to +70°C.........................................................8-Pin PDIP
SP805LEN.......................................................-40°C to +85°C....................................................8-Pin NSOIC
SP805LEP.......................................................-40°C to +85°C.......................................................8-Pin PDIP
SP805MCN.......................................................0°C to +70°C......................................................8-Pin NSOIC
SP805MCP.......................................................0°C to +70°C.........................................................8-Pin PDIP
SP805MEN......................................................-40°C to +85°C....................................................8-Pin NSOIC
SP805MEP......................................................-40°C to +85°C.......................................................8-Pin PDIP
Please consult the factory for pricing and availability on a Tape-On-Reel option.
Corporation
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation
Headquarters and
Sales Office
22 Linnell Circle
Billerica, MA 01821
TEL: (978) 667-8700
FAX: (978) 670-9001
e-mail: sales@sipex.com
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others.