LTC694-3.3/LTC695-3.3
3.3V Microprocessor
Supervisory Circuits
FEATURES
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DESCRIPTIO
®
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UL Recognized
File # E145770
Guaranteed
Reset Assertion at V
CC
= 1V
Pin Compatible with LTC694/LTC695
for 3.3V Systems
200µA Typical Supply Current
Fast (30ns Typ) On-Board Gating of
RAM Chip Enable Signals
SO-8 and S16 Packages
2.90V Precision Voltage Monitor
Power OK/Reset Time Delay: 200ms or Adjustable
Minimum External Component Count
1µA Maximum Standby Current
Voltage Monitor for Power-Fail or
Low-Battery Warning
Thermal Limiting
Performance Specified Over Temperature
The LTC
®
694-3.3/LTC695-3.3 provide complete 3.3V
power supply monitoring and battery control functions.
These include power-on reset, battery back-up, RAM write
protection, power failure warning and watchdog timing.
The devices are pin compatible upgrades of the LTC694/
LTC695 that are optimized for 3.3V systems. Operating
power consumption has been reduced to 0.6mW (typical)
and 3µW maximum in battery back-up mode. Micropro-
cessor reset and memory write protection are provided
when the supply falls below 2.9V. The RESET output is
guaranteed to remain logic low with V
CC
as low as 1V.
The LTC694-3.3/LTC695-3.3 power the active RAMs with
a charge pumped NMOS power switch to achieve low
dropout and low supply current. When primary power is
lost, auxiliary power, connected to the battery input pin,
powers the RAMs in standby through an efficient PMOS
switch.
For an early warning of impending power failure, the
LTC694-3.3/LTC695-3.3 provide an internal comparator
with a user-defined threshold. An internal watchdog timer
is also available, which forces the reset pins to active
states when the watchdog input is not toggled prior to a
preset time-out period.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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3.3V Low Power Systems
Critical
µP
Power Monitoring
Intelligent Instruments
Battery-Powered Computers and Controllers
Automotive Systems
TYPICAL APPLICATIO
V
IN
≥
5V
+
1µF
LT1129-3.3
V
IN
V
OUT
OUT SENSE
SHDN
GND
3.3V
+
100µF
0.1µF
V
CC
V
OUT
LTC695-3.3
V
BATT
CE IN
CE OUT
RESET
PFO
WDI
GND
RESET OUTPUT VOLTAGE (V)
2.4V
51k
PFI
18k
MICROPROCESSOR RESET, BATTERY BACK-UP,
RAM WRITE PROTECTION, POWER WARNING AND
WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR 3.3V MICROPROCESSOR SYSTEM
POWER TO
µP
CMOS RAM POWER
0.1µF
µP
SYSTEM
DECODER OUTPUT
RAM CS
µP
RESET
µP
NMI
I/O LINE
100Ω
0.1µF
694/5-3.3 TA01
U
RESET Output Voltage vs
Supply Voltage
5
4
3
2
1
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
5
694/5-3.3 TA02
U
U
1
LTC694-3.3/LTC695-3.3
ABSOLUTE
AXI U
RATI GS
Terminal Voltage
V
CC
...................................................... – 0.3V to 6V
V
BATT
.................................................. – 0.3V to 6V
All Other Inputs .................. – 0.3V to (V
OUT
+ 0.3V)
Input Current
V
CC
.............................................................. 100mA
V
BATT
............................................................ 25mA
GND .............................................................. 10mA
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
BATT
V
OUT
V
CC
GND
BATT ON
LOW LINE
OSC IN
OSC SEL
1
2
3
4
5
6
7
8
N PACKAGE
16-LEAD PDIP
16 RESET
15 RESET
14 WDO
13 CE IN
12 CE OUT
11 WDI
10 PFO
9
PFI
ORDER PART
NUMBER
LTC695CN-3.3
LTC695IN-3.3
T
JMAX
= 110°C,
θ
JA
= 130°C/W
TOP VIEW
V
OUT
V
CC
GND
1
2
3
8
7
6
5
N8 PACKAGE
8-LEAD PDIP
V
BATT
RESET
WDI
PFO
LTC694CN8-3.3
LTC694IN8-3.3
PFI 4
T
JMAX
= 110°C,
θ
JA
= 130°C/W
Consult factory for Military grade parts.
PRODUCT SELECTIO GUIDE
LTC694-3.3
LTC695-3.3
LTC690
LTC691
LTC694
LTC695
LTC699
LTC1232
LTC1235
PINS
8
16
8
16
8
16
8
8
16
RESET
THRESHOLD
(V)
2.90
2.90
4.65
4.65
4.65
4.65
4.65
4.37/4.62
4.65
WATCHDOG
TIMER
X
X
X
X
X
X
X
X
X
BATTERY
BACK-UP
X
X
X
X
X
X
POWER-FAIL
WARNING
X
X
X
X
X
X
RAM WRITE
PROTECT
X
X
X
X
X
PUSH-BUTTON
RESET
CONDITIONAL
BATTERY
BACK-UP
2
U
U
W
W W
U
U
W
(Notes 1 and 2)
V
OUT
Output Current ................. Short-Circuit Protected
Power Dissipation ............................................. 500mW
Operating Temperature Range
LTC694C-3.3/LTC695C-3.3 .................. 0°C to 70°C
LTC694I-3.3/LTC695I-3.3 ............... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
(Note 3)
TOP VIEW
V
BATT
1
V
OUT
2
V
CC
3
GND 4
BATT ON 5
LOW LINE 6
OSC IN 7
OSC SEL 8
16 RESET
15 RESET
14 WDO
13 CE IN
12 CE OUT
11 WDI
10 PFO
9 PFI
ORDER PART
NUMBER
LTC695CSW-3.3
LTC695ISW-3.3
SW PACKAGE
16-LEAD PLASTIC WIDE SO
T
JMAX
= 110°C,
θ
JA
= 130°C/W
TOP VIEW
V
OUT
V
CC
GND
PFI
1
2
3
4
8
7
6
5
VBATT
RESET
WDI
PFO
LTC694CS8-3.3
LTC694IS8-3.3
S8 PART
MARKING
6943
694I3
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 110°C,
θ
JA
= 180°C/W
X
X
X
X
LTC694-3.3/LTC695-3.3
The
q
denotes specifications which apply over the operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.3V, V
BATT
= 2V, unless otherwise noted.
PARAMETER
Battery Back-Up Switching
Operating Voltage Range
V
OUT
Output Voltage
V
CC
V
BATT
I
OUT
= 1mA
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
3.0
1.5
V
CC
– 0.1
V
CC
– 0.2
V
CC
– 0.8
V
BATT
– 0.1
TYP
MAX
5.50
2.75
UNITS
V
V
V
V
V
V
V
CC
– 0.01
V
CC
– 0.01
V
CC
– 0.4
V
BATT
– 0.02
0.2
0.2
0.04
0.04
0.6
1.0
1
5
0.02
0.10
70
50
20
I
OUT
= 50mA
V
OUT
in Battery Back-Up Mode
Supply Current (Exclude I
OUT
)
Supply Current in Battery Back-Up Mode
Battery Standby Current (+ = Discharge, – = Charge)
Battery Switchover Threshold (V
CC
– V
BATT
)
Battery Switchover Hysteresis
BATT ON Output Voltage (Note 4)
BATT ON Output Short-Circuit Current (Note 4)
Reset and Watchdog Timer
Reset Voltage Threshold
Reset Threshold Hysteresis
Reset Active Time
Watchdog Time-Out Period, Internal Oscillator
OSC SEL HIGH, V
CC
= 3V
I
SINK
= 800µA
BATT ON = V
OUT
, Sink Current
BATT ON = 0V, Source Current
I
OUT
= 250µA, V
CC
< V
BATT
I
OUT
≤
50mA, V
CC
= 3.6V
q
q
q
mA
mA
µA
µA
µA
µA
mV
mV
mV
V
CC
= 0V, V
BATT
= 2V
q
3.6V > V
CC
> V
BATT
+ 0.2V
q
– 0.02
– 0.10
Power Up
Power Down
q
q
0.3
0.5
2.8
160
140
1.2
1.0
80
70
4032
960
4
2
32
25
1
2.9
40
200
200
1.6
1.6
100
100
25
3.0
240
280
2.0
2.25
120
140
4097
1025
V
mA
µA
V
mV
ms
ms
sec
sec
ms
ms
Clock
Cycles
ms/V
ms/V
ms/V
ns
q
q
Long Period, V
CC
= 3V
q
Short Period, V
CC
= 3V
q
Watchdog Time-Out Period, External Clock (Note 5)
Reset Active Time PSRR
Watchdog Time-Out Period PSRR, Internal OSC
Minimum WDI Input Pulse Width
RESET Output Voltage at V
CC
= 1V
RESET and LOW LINE Output Voltage (Note 4)
RESET and WDO Output Voltage (Note 4)
RESET, RESET, WDO, LOW LINE
Output Short-Circuit Current (Note 4)
Long Period, V
CC
= 3V
Short Period, V
CC
= 3V
Short Period
Long Period
V
IL
= 0.4V, V
IH
= 3V
I
SINK
= 10µA, V
CC
= 1V
I
SINK
= 400µA, V
CC
= 2.8V
I
SOURCE
= 0.1µA, V
CC
= 3V
I
SINK
= 400µA, V
CC
= 3V
I
SOURCE
= 0.1µA, V
CC
= 2.8V
Output Source Current
Output Sink Current
q
q
q
q
q
q
q
q
q
200
4
2.3
0.3
2.3
1
3
9
25
200
0.3
mV
V
V
V
V
µA
mA
3
LTC694-3.3/LTC695-3.3
ELECTRICAL CHARACTERISTICS
PARAMETER
WDI Input Threshold
WDI Input Current
Power-Fail Detector
PFI Input Threshold
PFI Input Threshold PSRR
PFI Input Current
PFO Output Voltage (Note 4)
PFO Short-Circuit Source Current (Note 4)
PFI Comparator Response Time (Falling)
PFI Comparator Response Time (Rising) (Note 4)
Chip Enable Gating
CE IN Threshold
CE IN Pull-Up Current (Note 6)
CE OUT Output Voltage
V
IL
V
IH
The
q
denotes specifications which apply over the operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.3V, V
BATT
= 2V, unless otherwise noted.
CONDITIONS
Logic Low
Logic High
WDI = V
OUT
WDI = 0V
q
q
q
q
MIN
2.3
– 50
1.25
TYP
MAX
0.4
UNITS
V
V
µA
µA
V
mV/V
nA
V
V
µA
mA
µs
µs
µs
4
–8
1.3
0.3
±0.01
50
q
1.35
±25
0.3
q
I
SINK
= 800µA
I
SOURCE
= 0.1µA
PFI = HIGH, PFO = 0V
PFI = LOW, PFO = V
OUT
∆V
IN
= – 20mV, V
OD
= 15mV
∆V
IN
= 20mV, V
OD
= 15mV
with 10kΩ Pull-Up
q
q
q
2.3
1
3
17
2
40
8
0.45
1.9
3
25
V
V
µA
V
V
V
ns
mA
mA
µA
µA
I
SINK
= 800µA
I
SOURCE
= 400µA
I
SOURCE
= 1µA, V
CC
= 0V
C
L
= 20pF
Output Source Current
Output Sink Current
q
q
q
q
0.3
V
OUT
– 0.50
V
OUT
– 0.05
30
15
20
±2
5
50
CE IN Propagation Delay
CE OUT Output Short-Circuit Current
Oscillator
OSC IN Input Current (Note 6)
OSC SEL Input Pull-Up Current (Note 6)
OSC IN Frequency Range
OSC SEL = 0V
OSC SEL = 0V, C
OSC
= 47pF
q
0
4
125
kHz
kHz
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of device may be impaired.
Note 2:
All voltage values are with respect to GND.
Note 3:
For military temperature range parts, consult the factory.
Note 4:
The output pins of BATT ON, LOW LINE, PFO, WDO, RESET and
RESET have weak internal pullups of typically 3µA. However, external pull-
up resistors may be used when higher speed is required.
Note 5:
The external clock feeding into the circuit passes through the
oscillator before clocking the watchdog timer. Variation in the time-out
period is caused by phase errors which occur when the oscillator divides
the external clock by 64. The resulting variation in the time-out period is
64 plus one clock of jitter.
Note 6:
The input pins of CE IN, OSC IN and OSC SEL have weak internal
pull-ups which pull to the supply when the input pins are floating.
4
LTC694-3.3/LTC695-3.3
TYPICAL PERFOR A CE CHARACTERISTICS
Output Voltage vs Load Current
3.30
3.25
OUTPUT VOLTAGE (V)
2.40
PFI INPUT THRESHOLD (V)
V
CC
= 3.3V
V
BATT
= 2.4V
T
A
= 25
°
C
OUTPUT VOLTAGE (V)
3.20
SLOPE = 4.6Ω
3.15
3.10
3.05
3.00
0
10
30
40
20
LOAD CURRENT (mA)
50
Power-Fail Comparator
Response Time
PFO OUTPUT VOLTAGE (V)
3.5
PFO OUTPUT VOLTAGE (V)
PFO OUTPUT VOLTAGE (V)
3.0
2.5
2.0
1.5
1.0
0.5
0
V
PFI
1.3V
+
–
V
CC
= 3.3V
T
A
= 25
°
C
1.305V
1.285V
0
1
V
PFI
= 20mV STEP
2
3 4 5
TIME (µs)
6
Reset Active Time vs
Temperature
220
210
RESET ACTIVE TIME (ms)
V
CC
= 3.3V
RESET VOLTAGE THRESHOLD (V)
200
190
180
170
160
150
–50 –25
2.88
2.87
2.86
2.85
2.84
–50 –25
RESET OUTPUT VOLTAGE (V)
50
25
75
0
TEMPERATURE (
°
C)
U W
694/5-3.3 G01
Output Voltage vs Load Current
V
CC
= 0V
V
BATT
= 2.4V
T
A
= 25
°
C
1.310
1.308
1.306
1.304
1.302
1.300
1.298
1.296
Power Failure Input Threshold
vs Temperature
V
CC
= 3.3V
2.39
2.38
SLOPE = 90Ω
2.37
2.36
2.35
0
100
300
400
200
LOAD CURRENT (µA)
500
1.294
–50 –25
50
25
75
0
TEMPERATURE (
°
C)
100
125
694/5-3.3 G02
694/5-3.3 G03
Power-Fail Comparator
Response Time
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.315V
1.295V
V
PFI
1.3V
+
–
PFO
30pF
Power-Fail Comparator
Response Time with Pull-Up
Resistor
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.315V
1.295V
0
2
4
V
PFI
1.3V
+
–
3.3V
10k
PFO
30pF
V
CC
= 3.3V
T
A
= 25
°
C
V
CC
= 3.3V
T
A
= 25
°
C
PFO
30pF
V
PFI
= 20mV STEP
0
20 40
60 80 100 120 140 160 180
TIME (µs)
694/5-3.3 G05
V
PFI
= 20mV STEP
6
8 10 12 14 16 18
TIME (µs)
694/5-3.3 G06
7
8
9
694/5-3.3 G04
Reset Voltage Threshold vs
Temperature
2.90
V
CC
= 3.3V
2.89
RESET Output Voltage vs
Supply Voltage
5
4
3
2
1
100
125
50
25
75
0
TEMPERATURE (
°
C)
100
125
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
5
694/5-3.3 TA02
694/5-3.3 G07
694/5-3.3 G08
5
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