LTC2935
Ultra-Low Power Supervisor
with Power-Fail Output,
Selectable Thresholds
FEATURES
n
n
n
n
n
n
n
n
n
DESCRIPTION
The LTC
®
2935 ultra-low power voltage monitor provides
system initialization, power-fail warning and reset gen-
eration functions. Low quiescent current (500nA typical)
makes the LTC2935 an ideal choice for battery-operated
applications.
Three binary threshold-select inputs configure one of
eight integrated reset thresholds, ranging from 1.6V to
3.45V in pre-determined increments. Early warning of an
impending low voltage condition is provided at the power-
fail output (PFO), whose threshold is above the configured
reset threshold. Supervisory circuits monitor V
CC
and
pull
RST
low when V
CC
drops below the configured reset
threshold. When V
CC
is rising from an under-threshold
condition, an internal reset timer is started after exceeding
the reset threshold by 5%. A 200ms reset timeout delays
the return of the
RST
output to a high state. A pushbut-
ton switch connected to the
MR
input is typically used to
force a manual reset. Outputs
RST
and
PFO
are available
with open-drain (LTC2935-1/LTC2935-3) or active pull-up
(LTC2935-2/LTC2935-4) circuits. Operating temperature
range is from –40°C to 85°C.
500nA Quiescent Current
±1.5% (Max) Accuracy over Temperature
Integrated Precision Attenuators
Eight Pin-Selectable Reset Thresholds
Eight Pin-Selectable Power-Fail Thresholds
Early Warning Power-Fail Output
200ms Reset Timeout
Manual Reset Input
Compact 8-Lead, 2mm
×
2mm DFN and
TSOT-23 (ThinSOT™) Packages
APPLICATIONS
n
n
n
n
n
Portable Equipment
Battery-Powered Equipment
Security Systems
Point-of-Sale Devices
Wireless Systems
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
Falling Threshold Selection Table
Configurable Low Power Voltage Monitor
V
IN
V
CC
0.1μF
S2
S1
S0
MR
GND
2935 TA01a
LTC2935-1/LTC2935-2
LTC2935-3/LTC2935-4
PFO
LTC2935-2
BATTERY
POWERED
SYSTEM
LOGIC
RST
RESET
POWER-FAIL
RESET
POWER-FAIL
THRESHOLD THRESHOLD THRESHOLD THRESHOLD
(V)
(V)
(V)
(V)
3.30
3.15
3.00
2.85
2.70
2.55
2.40
2.25
3.45
3.30
3.15
3.00
2.85
2.70
2.55
2.40
2.44
2.32
2.20
2.08
1.96
1.84
1.72
1.60
2.56
2.44
2.32
2.20
2.08
1.96
1.84
1.72
S2
Low
Low
Low
Low
High
High
High
High
S1
Low
Low
High
High
High
Low
Low
High
S0
Low
High
High
Low
Low
Low
High
High
2935fa
1
LTC2935
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Input Voltages
V
CC
........................................................... –0.3V to 6V
S2, S1, S0,
MR
.........................–0.3V to (V
CC
+ 0.3V)
Output Voltages (PFO,
RST)
LTC2935-1/LTC2935-3 ............................. –0.3V to 6V
LTC2935-2/LTC2935-4 ..............–0.3V to (V
CC
+ 0.3V)
RMS Currents
PFO, RST
..........................................................±5mA
Operating Ambient Temperature Range
LTC2935C ................................................ 0°C to 70°C
LTC2935I.............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
TSOT-23 Package.............................................. 300°C
PIN CONFIGURATION
TOP VIEW
V
CC
1
MR
2
RST
3
PFO
4
9
8 S2
7 S1
6 S0
5 GND
S2 1
S1 2
S0 3
GND 4
TOP VIEW
8 V
CC
7
MR
6
RST
5
PFO
DC PACKAGE
8-LEAD (2mm 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 102°C/W
EXPOSED PAD (PIN 9), PCB GND CONNECTION OPTIONAL
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 195°C/W
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
LTC2935CTS8-1#TRMPBF
LTC2935ITS8-1#TRMPBF
LTC2935CTS8-2#TRMPBF
LTC2935ITS8-2#TRMPBF
LTC2935CTS8-3#TRMPBF
LTC2935ITS8-3#TRMPBF
LTC2935CTS8-4#TRMPBF
LTC2935ITS8-4#TRMPBF
LTC2935CDC-1#TRMPBF
LTC2935IDC-1#TRMPBF
LTC2935CDC-2#TRMPBF
LTC2935IDC-2#TRMPBF
LTC2935CDC-3#TRMPBF
LTC2935IDC-3#TRMPBF
LTC2935CDC-4#TRMPBF
LTC2935IDC-4#TRMPBF
TAPE AND REEL
LTC2935CTS8-1#TRPBF
LTC2935ITS8-1#TRPBF
LTC2935CTS8-2#TRPBF
LTC2935ITS8-2#TRPBF
LTC2935CTS8-3#TRPBF
LTC2935ITS8-3#TRPBF
LTC2935CTS8-4#TRPBF
LTC2935ITS8-4#TRPBF
LTC2935CDC-1#TRPBF
LTC2935IDC-1#TRPBF
LTC2935CDC-2#TRPBF
LTC2935IDC-2#TRPBF
LTC2935CDC-3#TRPBF
LTC2935IDC-3#TRPBF
LTC2935CDC-4#TRPBF
LTC2935IDC-4#TRPBF
PART MARKING*
LTDPW
LTDPW
LTDQB
LTDQB
LTFHV
LTFHV
LTFHX
LTFHX
LDPX
LDPX
LDQC
LDQC
LFHW
LFHW
LFHY
LFHY
PACKAGE DESCRIPTION
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead (2mm
×
2mm) Plastic DFN
8-Lead (2mm
×
2mm) Plastic DFN
8-Lead (2mm
×
2mm) Plastic DFN
8-Lead (2mm
×
2mm) Plastic DFN
8-Lead (2mm
×
2mm) Plastic DFN
8-Lead (2mm
×
2mm) Plastic DFN
8-Lead (2mm
×
2mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
8-Lead (2mm
×
2mm) Plastic DFN
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
2935fa
2
LTC2935
ELECTRICAL CHARACTERISTICS
SYMBOL
V
CC
I
CC
V
RTF1
V
RTF2
V
RTF3
V
RTF4
V
RTF5
V
RTF6
V
RTF7
V
RTF8
ΔV
RTF
V
RT(HYST)
t
UVR
V
RTF1
V
RTF2
V
RTF3
V
RTF4
V
RTF5
V
RTF6
V
RTF7
V
RTF8
ΔV
RTF
V
RT(HYST)
t
UVR
ΔV
PFT
PARAMETER
V
CC
Input Supply Voltage
V
CC
Input Supply Current
Reset Threshold 1 (V
CC
Falling)
Reset Threshold 2 (V
CC
Falling)
Reset Threshold 3 (V
CC
Falling)
Reset Threshold 4 (V
CC
Falling)
Reset Threshold 5 (V
CC
Falling)
Reset Threshold 6 (V
CC
Falling)
Reset Threshold 7 (V
CC
Falling)
Reset Threshold 8 (V
CC
Falling)
Reset Threshold Differential V
RTF(N+1)
– V
RTF(N)
Reset Threshold Hysteresis (V
CC
Rising)
Undervoltage Detect to
RST
Falling
Reset Threshold 1 (V
CC
Falling)
Reset Threshold 2 (V
CC
Falling)
Reset Threshold 3 (V
CC
Falling)
Reset Threshold 4 (V
CC
Falling)
Reset Threshold 5 (V
CC
Falling)
Reset Threshold 6 (V
CC
Falling)
Reset Threshold 7 (V
CC
Falling)
Reset Threshold 8 (V
CC
Falling)
Reset Threshold Differential V
RTF(N+1)
– V
RTF(N)
Reset Threshold Hysteresis (V
CC
Rising)
Undervoltage Detect to
RST
Falling
Power-Fail Threshold Differential V
PFT(N)
– V
RTF(N)
S2 = Low : S1 = Low : S0 = Low
S2 = Low : S1 = Low : S0 = High
S2 = Low : S1 = High : S0 = High
S2 = Low : S1 = High : S0 = Low
S2 = High : S1 = High : S0 = Low
S2 = High : S1 = Low : S0 = Low
S2 = High : S1 = Low : S0 = High
S2 = High : S1 = High : S0 = High
(Note 3)
Relative to Any Selected Reset Threshold
V
CC
Below Threshold by 1% (Note 3)
S2 = Low : S1 = Low : S0 = Low
S2 = Low : S1 = Low : S0 = High
S2 = Low : S1 = High : S0 = High
S2 = Low : S1 = High : S0 = Low
S2 = High : S1 = High : S0 = Low
S2 = High : S1 = Low : S0 = Low
S2 = High : S1 = Low : S0 = High
S2 = High : S1 = High : S0 = High
(Note 3)
Relative to Any Selected Reset Threshold
V
CC
Below Threshold by 1% (Note 3)
Any Selected Reset Threshold (V
CC
Falling)
Relative to Any Selected Power-Fail Threshold
(V
CC
Rising)
V
CC
Below Threshold by 1% (Note 3)
Any Selected Reset Threshold (V
CC
Falling)
Relative to Any Selected Power-Fail Threshold
(V
CC
Rising)
V
CC
Below Threshold by 1% (Note 3)
S2, S1, S0
MR
MR
Manual Reset Falling
MR
S2, S1, S0 = V
CC
or GND
l
0.3 • V
CC
l
0.4
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.6V, unless otherwise noted. (Note 2)
CONDITIONS
l
l
l
l
l
l
l
l
l
l
l
l
MIN
225
3.251
3.103
2.955
2.808
2.660
2.512
2.364
2.217
142
4.5
TYP
500
3.300
3.150
3.000
2.850
2.700
2.550
2.400
2.250
150
5
1
MAX
5.5
1000
3.349
3.197
3.045
2.892
2.740
2.588
2.436
2.283
158
6
UNITS
V
nA
V
V
V
V
V
V
V
V
mV
%
ms
Reset Thresholds (LTC2935-1/LTC2935-2)
Reset Thresholds (LTC2935-3/LTC2935-4)
2.404
2.286
2.167
2.049
1.931
1.813
1.695
1.576
112
4.5
2.440
2.320
2.200
2.080
1.960
1.840
1.720
1.600
120
5
1
100
2
150
2.5
1
70
2
120
2.5
1
0.7 • V
CC
1.4
5
900
±1
20
1200
±10
170
3
200
3.5
2.476
2.354
2.233
2.111
1.989
1.867
1.745
1.624
128
6
V
V
V
V
V
V
V
V
mV
%
ms
mV
%
ms
mV
%
ms
V
V
μs
μs
kΩ
nA
2935fa
Power-Fail Thresholds (LTC2935-1/LTC2935-2)
V
PFT(HYST)
Power-Fail Threshold Hysteresis
t
UVP
ΔV
PFT
Undervoltage Detect to
PFO
Falling
Power-Fail Threshold Differential V
PFT(N)
– V
RTF(N)
Power-Fail Thresholds (LTC2935-3/LTC2935-4)
V
PFT(HYST)
Power-Fail Threshold Hysteresis
t
UVP
V
IN(TH)
t
PW
t
PD
R
PU
I
LK
Undervoltage Detect to
PFO
Falling
Control Input Threshold
Input Pulse Width
Propagation Delay to
RST
Falling
Internal Pull-Up Resistance
Input Leakage Current
Control Inputs:
MR,
S2, S1, S0
20
2
600
3
LTC2935
ELECTRICAL CHARACTERISTICS
SYMBOL
V
OL
PARAMETER
Voltage Output Low
Reset and Power-Fail Outputs:
RST, PFO
V
CC
= 1V, 200μA Pull-Up Current
V
CC
= 3V, 3mA Pull-Up Current
S2, S1, S0 = Low
–200μA Pull-Down Current
V
RST
, V
PFO
= 3.6V
l
l
l
0.7 • V
CC
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.6V, unless otherwise noted. (Note 2)
CONDITIONS
MIN
TYP
25
50
MAX
100
150
UNITS
mV
mV
V
±1
140
200
±10
260
nA
ms
V
OH
I
OH
t
RST
Voltage Output High (LTC2935-2)
Current Output High, Leakage (LTC2935-1)
Reset Timeout Period
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2.
All currents into pins are positive, all voltages are referenced to
GND unless otherwise noted.
Note 3.
Guaranteed by design. Characterized, but not production tested.
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
1000
S0 = S1 = S2 = GND
NORMALIZED THRESHOLD (V/ V)
85°C
1.015
1.010
1.005
1.000
0.995
0.990
0.985
–50
T
A
= 25°C, unless otherwise noted.
Comparator Undervoltage
Glitch Immunity
3.0
2.5
2.0
1.5
1.0
0.5
0
0.1
V
CC
= 3.6V
Normalized Reset and Power-Fail
Thresholds vs Temperature
GLITCH DURATION, t
UV
(ms)
800
I
CC
(nA)
600
25°C
–40°C
COMPARATORS PULL DOWN
ABOVE CURVE
400
200
0
0
1
2
3
V
CC
(V)
4
5
6
2935 G01
–25
0
25
50
TEMPERATURE (°C)
75
100
2935 G02
1
10
COMPARATOR OVERDRIVE (%)
100
2935 G03
Reset Timeout Period
vs Temperature
260
240
220
t
RST
(ms)
V
OL
(mV)
60
200
180
V
CC
= 3.6V
100
Voltage Output Low vs Pull-Up
Current (RST,
PFO)
3.6
V
CC
= 3V
85°C
3.5
25°C
V
OH
(mV)
–40°C
40
Voltage Output High vs Pull-Down
Current (RST,
PFO)
LTC2935-2
V
CC
= 3.6V
80
–40°C
3.4
25°C
3.3
160
140
–50
20
85°C
–25
0
25
50
TEMPERATURE (°C)
75
100
2935 G04
0
3.2
0
1
2
3
4
PULL-UP CURRENT (mA)
5
2935 G05
0
–0.4
–0.6
–0.8
–0.2
PULL-DOWN CURRENT (mA)
–1
2935 G06
2935fa
4
LTC2935
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs S0, S1, S2
Input Voltage
250
V
CC
= 3.6V
5
T
A
= 25°C, unless otherwise noted.
Supply Current vs
MR
Input Voltage
V
CC
= 3.6V
200
4
I
CC
(μA)
100
I
CC
(μA)
1
1.5
2
2.5
3
4
2935 G07
150
3
2
50
1
0
0
0.5
3.5
S0, S1, S2 INPUT VOLTAGE (V)
0
0
0.5
1
1.5
2
2.5
3
3.5
4
2935 G08
MR
INPUT VOLTAGE (V)
PIN FUNCTIONS
Exposed Pad (DFN Only):
Exposed Pad may be left floating
or connected to device ground.
GND:
Device ground.
MR:
Manual Reset Input. Attach a pushbutton switch
between this input and ground. A logic low on this input
pulls
RST
low. When the
MR
input returns to logic high,
RST
returns high after 200ms. Tie to V
CC
if unused.
PFO:
Power-Fail Output.
PFO
pulls low when V
CC
falls
below the power-fail threshold. The power-fail thresh-
old is above the configured falling reset threshold by a
pre-determined margin.
PFO
is released when V
CC
rises
above the power-fail threshold by 2.5%.
PFO
is available
with open-drain (LTC2935-1/LTC2935-3) or active pull-up
(LTC2935-2/LTC2935-4) outputs. Leave open if unused.
RST:
Reset Output.
RST
pulls low when V
CC
falls below the
reset threshold.
RST
is released 200ms after V
CC
exceeds
the reset threshold plus 5% hysteresis.
RST
is available
with open-drain (LTC2935-1/LTC2935-3) or active pull-up
(LTC2935-2/LTC2935-4) outputs. Leave open if unused.
S2, S1, S0:
Threshold Selection Inputs. Tie to GND or
V
CC
for required reset threshold. See the Falling Threshold
Selection Table on page 1 for settings.
V
CC
:
Power Supply and Monitored Voltage Input. Bypass
V
CC
with a 0.1μF capacitor to GND.
2935fa
5
微控制器 MCU
