LTC2903CS6-A1#PBF [Linear]
LTC2903-1 - Precision Quad Supply Monitor in 6-Lead SOT-23; Package: SOT; Pins: 6; Temperature Range: 0°C to 70°C;
| 型号： | LTC2903CS6-A1#PBF |
| 厂家： | 
Linear |
| 描述： | LTC2903-1 - Precision Quad Supply Monitor in 6-Lead SOT-23; Package: SOT; Pins: 6; Temperature Range: 0°C to 70°C 光电二极管 |
| 文件： | 总16页 (文件大小：153K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC2903-1
Precision Quad Supply
Monitor in 6-Lead SOT-23
U
FEATURES
DESCRIPTIO
The LTC®2903-1 monitors up to four supply voltages. The
common reset output remains low until all four inputs
have been in compliance for 200ms. Voltage thresholds
maintain ±1.5% accuracy over temperature (with respect
to the monitored voltage). The LTC2903-1 features an
open-drain RST output with a weak internal pullup.
■
Ultralow Voltage Reset: VCC = 0.5V Guaranteed
Monitor Four Inputs Simultaneously
■
3.3V, 2.5V, 1.8V, ADJ (LTC2903-A1)
5V, 3.3V, 2.5V, 1.8V (LTC2903-B1)
5V, 3.3V, 1.8V, –5.2V (LTC2903-C1)
3.3V, ADJ, ADJ, ADJ (LTC2903-D1)
5V, ADJ, ADJ, ADJ (LTC2903-E1)
Internalsupplyvoltage(VCC)isgeneratedfromthegreater
voltageontheV1,V2inputs.VCC =V1forLTC2903-D1and
LTC2903-E1. TheRSToutputisguaranteedtosinkatleast
5µA (VOL = 0.15V) for VCC down to 0.5V and will typically
conduct current down to 0V. Quiescent current is 20µA
typical, making the LTC2903-1 ideal for power conscious
systems.TheLTC2903-1isavailableina6-leadlowprofile
(1mm) SOT-23 package.
■
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage over Temperature
■
10% (A1, B1, C1) and 5% (D1, E1) Undervoltage
Monitoring
■
Low Supply Current: 20µA Typical
■
200ms Reset Time Delay
■
Active Low Open-Drain RST Output
■
Power Supply Glitch Immunity
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
Low Profile (1mm) SOT-23 (ThinSOTTM) Package
■
U
APPLICATIO S
■
Multivoltage Systems
■
Optical Networking Systems
■
Cell Phone Base Stations
Network Servers
■
U
TYPICAL APPLICATIO
Low Voltage Reset Pull-Down Performance
vs External Pull-Up Current and Input Supply Voltage
0.10
V
= V1 = V2 = V3
IN
5V
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
LTC2903-B1
3.3V
DC/DC
CONVERTER
SYSTEM
LOGIC
2.5V
1.8V
20µA
10µA
LTC2903-B1
V1
RST
C1
5µA
2µA
0.1µF
GND
V2
V4
C2
0.1µF
V3
2903 TA01
1µA
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
, INPUT SUPPLY VOLTAGE (V)
0
1
V
IN
2903 TA01b
29031f a
1
LTC2903-1
W W
U W
U
W U
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2, 3)
PACKAGE/ORDER INFORMATION
TOP VIEW
V1, V2...................................................... –0.3V to 6.5V
V3 ................................................. 2.7V or (VCC + 0.3V)
V4 (LTC2903-A1, -B1, -D1, -E1) ...............–0.3V to 6.5V
V4 (LTC2903-C1) .................................... –6.5V to 0.3V
RST ........................................................ –0.3V to 6.5V
Operating Temperature Range
V1 1
GND 2
V2 3
6 RST
5 V4
4 V3
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
TJMAX = 125°C, θJA = 230°C/W
LTC2903C-X1 .......................................... 0°C to 70°C
LTC2903I-X1 ...................................... –40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART NUMBER
S6 PART MARKING
LTC2903CS6-A1
LTC2903CS6-B1
LTC2903CS6-C1
LTC2903CS6-D1
LTC2903CS6-E1
LTC2903IS6-A1
LTC2903IS6-B1
LTC2903IS6-C1
LTC2903IS6-D1
LTC2903IS6-E1
LTAFV
LTAJN
LTAJQ
LTBMX
LTBMZ
LTAFW
LTAJP
LTAJR
LTBMY
LTBNB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
(LTC2903-A1) The ● denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
2.970
2.250
1.620
0.508
UNITS
V
V
V
V
3.3V, 10% Reset Threshold
2.5V, 10% Reset Threshold
1.8V, 10% Reset Threshold
Adjustable Reset Threshold
V1 Input Threshold
V2 Input Threshold
V3 Input Threshold
V4 Input Threshold
●
●
●
●
2.871
2.175
1.566
0.492
2.921
2.213
1.593
0.500
V
V
V
V
RT33
RT25
RT18
RTA
(LTC2903-B1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. VCC = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
4.500
2.970
2.250
1.620
UNITS
V
RT50
V
RT33
V
RT25
V
RT18
5V, 10% Reset Threshold
3.3V, 10% Reset Threshold
2.5V, 10% Reset Threshold
1.8V, 10% Reset Threshold
V1 Input Threshold
V2 Input Threshold
V3 Input Threshold
V4 Input Threshold
●
●
●
●
4.350
2.871
2.175
1.566
4.425
2.921
2.213
1.593
V
V
V
V
(LTC2903-C1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. VCC = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
4.500
2.970
1.620
UNITS
V
V
V
V
5V, 10% Reset Threshold
3.3V, 10% Reset Threshold
1.8V, 10% Reset Threshold
–5.2V, 10% Reset Threshold
V1 Input Threshold
V2 Input Threshold
V3 Input Threshold
V4 Input Threshold
●
●
●
●
4.350
2.871
1.566
4.425
2.921
1.593
V
RT50
RT33
RT18
RT52N
V
V
V
–4.524 –4.602 –4.680
29031f a
2
LTC2903-1
ELECTRICAL CHARACTERISTICS
(LTC2903-D1) The ● denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
3.135
0.508
0.508
0.508
UNITS
V
V
V
V
3.3V, 5% Reset Threshold
V2 Adjustable Threshold
V3 Adjustable Threshold
V4 Adjustable Threshold
V1 Input Threshold
V2 Input Threshold
V3 Input Threshold
V4 Input Threshold
●
●
●
●
3.036
0.492
0.492
0.492
3.086
0.500
0.500
0.500
V
V
V
V
RT33
RTAV2
RTAV3
RTAV4
(LTC2903-E1) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. VCC = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
4.750
0.508
0.508
0.508
UNITS
V
V
V
V
5V, 5% Reset Threshold
V2 Adjustable Threshold
V3 Adjustable Threshold
V4 Adjustable Threshold
V1 Input Threshold
V2 Input Threshold
V3 Input Threshold
V4 Input Threshold
●
●
●
●
4.600
0.492
0.492
0.492
4.675
0.500
0.500
0.500
V
V
V
V
RT50
RTAV2
RTAV3
RTAV4
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VCC = 3.3V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
I
I
I
V1 Input Current (Note 4)
V1 = 3.3V (LTC2903-A1, LTC2903-D1)
V1 = 5V (LTC2903-B1, LTC2903-C1,
LTC2903-E1)
●
●
20
25
80
80
µA
µA
V1
V2
V3
V4
V2 Input Current (Note 4)
V3 Input Current
V2 = 2.5V (LTC2903-A1)
V2 = 3.3V (LTC2903-B1, LTC2903-C1)
V2 = 0.55V (LTC2903-D1, LTC2903-E1)
●
●
●
8
10
30
30
±30
µA
µA
nA
V3 = 1.8V (LTC2903-A1, LTC2903-C1)
V3 = 2.5V (LTC2903-B1)
V3 = 0.55V (LTC2903-D1, LTC2903-E1)
●
●
●
8
10
30
30
±30
µA
µA
nA
V4 Input Current
V4 = 0.55V (LTC2903-A1)
V4 = 1.8V (LTC2903-B1)
V4 = –5.2V (LTC2903-C1)
V4 = 0.55V (LTC2903-D1, LTC2903-E1)
●
●
●
●
±30
4
–6
nA
µA
µA
nA
2
–3
±30
t
t
Reset Time-Out Period
●
140
200
150
260
ms
RST
UV
V Undervoltage Detect to RST
X
V Less Than Threshold V
More Than 1%
by
µs
X
RTX
V
V
Output Voltage High RST (LTC2903-1) (Note 5)
Output Voltage Low RST (Note 6)
I
= –1µA (LTC2903-A1,
RST(DN)
●
●
V2 – 1
V1 – 1
V
V
OH
OL
LTC2903-B1, LTC2903-C1)
(LTC2903-D1, LTC2903-E1)
V
V
V
V
= 0.2V, I
= 0.5V, I
= 0.1µA
= 5µA
= 200µA
●
●
●
●
5
10
25
100
60
mV
mV
mV
mV
CC
CC
CC
CC
RST
150
300
300
RST
= 1V, I
= 3V, I
RST
RST
= 2500µA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
from the V1 input. When V2 exceeds V1, V2 supplies the quiescent
current. V1 only for options D1 and E1.
Note 2: All currents into pins are positive, all voltages are referenced to
GND unless otherwise noted.
Note 5: The RST output pin on the LTC2903-1 has an internal pull-up to
V2 (for options A1, B1 and C1) of typically 10µA. However, for faster rise
times or for V voltages greater than V2, use an external pull-up resistor.
The internal pull-up is connected to V1 for options D1 and E1.
OH
Note 3: The internal supply voltage (V ) is generated from the greater
CC
voltage on the V1 and V2 inputs. V = V1 for options D1 and E1.
CC
Note 6: For options A1, B1 and C1, the RST pulldown current is derived
from V1, V2 and V3. For options D1 and E1, pulldown strength is derived
Note 4: Under typical operating conditions, quiescent current is drawn
from V1.
29031f a
3
LTC2903-1
TYPICAL PERFOR A CE CHARACTERISTICS
U W
5V Threshold Voltage
vs Temperature
3.3V Threshold Voltage
vs Temperature
2.5V Threshold Voltage
vs Temperature
2.975
2.950
2.925
2.900
2.875
4.500
4.475
4.450
4.425
4.400
4.375
4.350
2.250
2.235
2.220
2.205
2.190
2.175
–50
0
25
50
75
100
–50
0
25
50
75
100
–50
0
25
50
75
100
–25
–25
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
29031 G01
29031 G02
29031 G03
1.8V Threshold Voltage
vs Temperature
ADJ Threshold Voltage
vs Temperature
–5.2V Threshold Voltage
vs Temperature
1.625
1.615
1.605
1.595
1.585
1.575
1.565
0.510
0.505
0.500
0.495
0.490
–4.530
–4.555
–4.580
–4.605
–4.630
–4.655
–4.680
–50
0
25
50
75
100
–50
0
25
50
75
100
–50
0
25
50
75
100
–25
–25
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
29031 G04
29031 G05
29031 G06
Supply Currents
vs Temperature (LTC2903-A1)
Supply Currents
vs Temperature (LTC2903-B1)
Supply Currents
vs Temperature (LTC2903-C1)
30
25
20
15
10
5
30
25
20
15
10
5
30
25
20
15
10
5
V1 = 3.3V
V2 = 2.5V
V3 = 1.8V
V1 = 5V
V1 = 5V
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
V2 = 3.3V
V3 = 1.8V
V4 = –5.2V
I
V1
I
V1
I
V1
I
V2
I
I
V2
V2
I
V3
I
V3
0
I
I
V4
V3
I
V4
0
0
–5
–50
0
25
50
75
100
–25
–50
0
25
50
75
100
–25
50
TEMPERATURE (°C)
100
–50 –25
0
25
75
TEMPERATURE (°C)
TEMPERATURE (°C)
29031 G07
29031 G08
29031 G09
29031f a
4
LTC2903-1
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Transient Duration
Reset Time-Out Period
vs Temperature
Supply Currents vs Temperature
vs Comparator Overdrive
260
240
220
200
180
160
140
400
350
300
250
200
150
100
50
25
20
15
10
5
LTC2903-E1
LTC2903-D1
RESET OCCURS
ABOVE CURVE
0
0
–50
0
25
50
75
100
0.1
1
10
100
)
–25
–50
0
25
50
75
100
–25
TEMPERATURE (°C)
RESET COMPARATOR OVERDRIVE (% OF V
TEMPERATURE (°C)
RTX
29031 G10
29301 G11
29031 G20
Low Voltage Reset Pull-Down
Performance vs External Pull-Up
Current and Input Supply Voltage
RST Output Voltage with 10k
Pull-Up to V1
RST Output Voltage with
10k Pull-Up to V1
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0.30
0.25
0.20
0.15
0.10
0.05
0
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
V1 = V2 = V3
LTC2903-B1, -C1
V
= V1 = V2 = V3
IN
20µA
10µA
V1 ONLY
5µA
2µA
V1 = V2 = V3
1µA
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
, INPUT SUPPLY VOLTAGE (V)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0
1
V1 (V)
V1 (V)
V
IN
29031 G12
29301 G13
29031 G14
RST Current Sink Capability
vs VCC
RST Voltage Output Low
vs RST Sink Current
RST Voltage Output Low
vs RST Sink Current
1.5
1.2
1.5
1.2
15
12
9
LTC2903-A1, -E1
V1 = 3.3V
LTC2903-B1, -C1, -D1
V1 = 5V
25°C
85°C
25°C
–45°C
85°C
–45°C
V
= 0.4V
OL
0.9
0.9
V
= 0.2V
OL
0.6
0.3
0
0.6
0.3
0
6
3
0
0
5
10 15 20 25 30 35 40 45
(mA)
0
10
20
30
(mA)
40
50
60
2
0
0.5
1
1.5
2.5
(V)
3
3.5
4
4.5
5
I
I
RST
RST
V
CC
29031 G16
29031 G16
29031 G15
29031f a
5
LTC2903-1
U W
TYPICAL PERFOR A CE CHARACTERISTICS
RST Pull-Up Current vs V2
RST Pull-Up Current vs V1
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
–80
–70
–60
–50
–40
–30
–20
–10
0
LTC2903-A1, -B1, -C1
V1, V3, V4 ABOVE THRESHOLD
LTC2903-D1, -E1
V2, V3, V4 ABOVE THRESHOLD
LTC2903-D1
V
V
LTC2903-E1
RT25
RT33
3.5
0
0.5
1
1.5
2
2.5
3
4
4.5
5
0
0.5
1
1.5
2
2.5
4
3 3.5 4.5
5 5.5
V2 (V)
V1 (V)
29031 G18
29031 G21
RST Pull-Up Current vs External
Pull-Down Voltage on RST
RST Pull-Up Current vs External
Pull-Down Voltage on RST
–80
–70
–60
–50
–40
–30
–20
–10
0
–40
–35
–30
LTC2903-E1
LTC2903-B1, -C1
LTC2903-A1
–25
–20
–15
–10
–5
LTC2903-D1
0
1
2
3
4
5
6
0
0.5
1
2
2.5
3
3.5
0
1.5
V
V
RST
(V)
(V)
RST
29031 G22
29031 G19
29031f a
6
LTC2903-1
U
U
U
PI FU CTIO S
V1 (Pin 1): Voltage Input 1. Internal VCC is generated from
the greater voltage on the V1 and V2 inputs. VCC = V1 for
options D1 and E1. Bypass this pin to ground with a 0.1µF
(or greater) capacitor.
V3 is an adjustable input for options D1 and E1. See Table
1b for recommended ADJ resistor values.
V4(Pin5):VoltageInput4. Table1liststherecommended
ADJ resistor values for options A1, B1 and C1. See Table
1b for options D1 and E1.
GND (Pin 2): Ground.
V2 (Pin 3): Voltage Input 2. Internal VCC is generated from
the greater voltage on the V1 and V2 inputs. VCC = V1 for
options D1 and E1. For option A1, B1, C1 bypass this pin
to ground with a 0.1µF (or greater) capacitor. V2 is an
adjustable input for options D1 and E1. See Table 1b for
recommended ADJ resistor values.
RST (Pin 6): Reset Logic Output. Pulls low when any volt-
age input is below reset threshold and held low for 200ms
after all voltage inputs exceed threshold. The pin contains
a weak pull-up to V2 (V1 for options D1 and E1). Use an
external pull-up for faster rise times or output voltages
greater than V2 (V1 for options D1 and E1).
V3(Pin4):VoltageInput3.ThisinputassiststheRSTpull-
down circuitry below 1V (for options A1, B1 and C1 only).
W U
W
TI I G DIAGRA
V
RTX
V
X
t
t
UV
RST
1.5V
29031 TD
RST
29031f a
7
LTC2903-1
BLOCK DIAGRA S
W
(LTC2903-A1, LTC2903-B1)
–
+
V1
V2
V3
1
3
4
V1
POWER
V
CC
DETECT
V2
V2
10µA
–
+
RESET DELAY GENERATOR
6
RST
200ms
DELAY
–
+
V1
LOW VOLTAGE
V2
PULL-DOWN
V3
MONITORED VOLTAGES
–
+
A1
B1
V4
5
2
V1
V2
V3
V4
3.3V
2.5V
1.8V
ADJ
5V
3.3V
2.5V
1.8V
BANDGAP
REFERENCE
GND
29031 BD1
0.5V
(LTC2903-C1)
–
+
V1
V2
V3
1
V1
V2
POWER
DETECT
V
CC
V2
10µA
–
+
3
4
RESET DELAY GENERATOR
6
RST
200ms
DELAY
–
+
V1
LOW VOLTAGE
V2
PULL-DOWN
V3
MONITORED VOLTAGES
+
–
V1
V2
V3
V4
5V
V4
5
2
3.3V
1.8V
–5.2V
BANDGAP
REFERENCE
GND
29031 BD3
29031f a
8
LTC2903-1
W
BLOCK DIAGRA S
(LTC2903-D1, LTC2903-E1)
–
+
V1
V2
V3
1
3
4
POWER
DETECT
V1
V
CC
V1
10µA
–
+
RESET DELAY GENERATOR
6
RST
200ms
DELAY
–
+
LOW VOLTAGE
V1
PULL-DOWN
MONITORED VOLTAGES
–
+
D1
E1
V4
5
2
V1
V2
V3
V4
3.3V
ADJ
ADJ
ADJ
5V
ADJ
ADJ
ADJ
BANDGAP
REFERENCE
GND
29031 BD2
0.5V
W U U
U
APPLICATIO S I FOR ATIO
Power-Up
When V1, V2 and V3 are ramped simultaneously (for
options A1, B1 and C1 only), the reset pull-down current
increases up to three times the current that may be pulled
with a single input. Figure 1 demonstrates the reset pin
The LTC2903-1 issues a logic low on the RST output when
an input supply voltage resides below the prescribed
threshold voltage. Ideally, the RST logic output would
remain low with the input supply voltage down to zero
volts. Most supervisors lack pull-down capability below
1V. The LTC2903-1 power supply supervisors incorporate
a new low voltage pull-down circuit that can hold the RST
line low with as little as 200mV of input supply voltage on
V1,V2orV3(V1onlyforoptionsD1andE1).Thepull-down
circuit helps maintain a low impedance path to ground,
reducing the risk of floating the RST node to undetermined
voltages. Such voltages may trigger external logic causing
erroneous reset operation(s). Furthermore, a mid-scale
voltage could cause external circuits to operate in the
middle of their voltage transfer characteristic, consuming
more quiescent current than normal. These conditions
could cause serious system reliability problems.
10000
T
= 25°C
RST
A
V
= 0.3V
CC
1000
100
10
V1 = V2 = V3
V1 ONLY
1
0
0.2
0.4
0.6
(V)
0.8
1.0
1.2
V
CC
29031 F01
Figure 1. RST Pull-Down Current vs VCC
29031f a
9
LTC2903-1
W U U
U
APPLICATIO S I FOR ATIO
Triple Adjustable Options (LTC2903-D1, LTC2903-E1)
current sinking ability for single supply and triple supply-
trackingapplications. Figure2showsadetailedviewofthe
reset pin voltage with a 10k pull-up resistor to V1.
LTC2903-D1 and LTC2903-E1 provide 3 adjustable in-
puts: V2, V3 and V4. The V1 threshold is 3.086V (3.3V,
5%) for option D1 and 4.675 (5V, 5%) for option E1. For
each supply monitored by an adjustable input, connect an
external resistor divider (R1 and R2) between the positive
voltage being sensed and ground. The tap point for each
divider is then connected to each adjustable input. All
adjustable inputs are compared to an internal 0.5V
reference.
The LTC2903-1 supervisors derive their internal supply
voltage(VCC)automaticallyfromthegreatervoltageonthe
V1 and V2 inputs (VCC = V1 for options D1 and E1). With
all supply inputs above threshold, the quiescent current
drawn from VCC is 20µA (typ).
Supply Monitoring
The LTC2903-1 accurately monitors four inputs in a small
6-lead SOT-23 package. The low voltage reset output
includes an integrated 200ms reset delay timer. The reset
line pulls high 200ms after all voltage inputs exceed their
respective thresholds. The reset output remains low dur-
ing power-up, power-down and brownout conditions on
any of the voltage inputs.
Figure 3 shows how each adjustable input is configured.
Calculate the trip voltage from:
R1
R2
⎛
⎝
⎞
⎟
⎠
VTRIP = 0.5V 1+
⎜
V
TRIP
LTC2903-A1
0.7
R1
T
= 25°C
A
V4
–
0.6
0.5
R2
COMPETITION
PART
+
+
0.5V
0.4
0.3
0.2
0.1
–
29031 F03
V1 ONLY
V1 = V2 = V3
Figure 3. Setting the Positive Adjustable Trip Point
0
0.4
0.5 0.6 0.7 0.8 0.9 1.0
0
0.3
0.1 0.2
V1 (V)
29031 F02
Figure 2. RST Output Voltage with a 10k Pull-Up to V1
(Enlarged Area of Detail)
29031f a
10
LTC2903-1
W U U
APPLICATIO S I FOR ATIO
U
Table 1a contains suggested 1% resistor values for the
ADJinputstoobtainnominal–11.5%thresholds.Connect
unused supervisor inputs to the highest supply voltage
available.
Implications of Threshold Accuracy
Specifying system voltage margin for worst-case opera-
tion requires consideration of three factors: power supply
tolerance, IC supply voltage tolerance and supervisor re-
set threshold accuracy. Highly accurate supervisors ease
the design challenge by decreasing the overall voltage
margin required for reliable system operation. Consider a
5V system with a ±10% power supply tolerance band.
System ICs powered by this supply must operate reliably
within this band (and a little more, as explained below).
The bottom of the supply tolerance band, at 4.5V (5V –
10%), is the exact voltage at which a perfectly accurate
supervisor generates a reset. Such a perfectly accurate
supervisor does not exist—the actual reset threshold may
vary over a specified band (±1.5% for the LTC2903-1 su-
pervisors). Figure 4 shows the typical relative threshold
accuracy for all four inputs, over temperature.
Table1a. Suggested1%ResistorValuesforthe–11.5%ADJInputs
V
(V)
V
TRIP
(V)
R1 (kΩ)
2050
1690
1330
1240
976
R2(kΩ)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
SUPPLY
12
10.75
8.95
10
8
7.15
7.5
6
6.7
5.38
5
4.435
2.935
2.66
787
3.3
3
487
432
2.5
1.8
1.5
1.2
1
2.2
340
1.605
1.325
1.065
0.884
0.795
221
165
With this variation of reset threshold in mind, the nominal
reset threshold of the supervisor resides below the mini-
mum supply voltage, just enough so that the reset thresh-
old band and the power supply tolerance bands do not
overlap. If the two bands overlap, the supervisor could
generate a false or nuisance reset when the power supply
remains within its specified tolerance band (say, at 4.6V).
113
76.8
59
0.9
Table 1b contains suggested 1% resistor values for the
ADJ inputs to obtain nominal –6.5% thresholds.
Table 1b. Suggested 1% Resistor Values for the –6.5% ADJ Inputs
Adding half of the reset threshold accuracy spread (1.5%)
to the ideal 10% thresholds puts the LTC2903-1 thresh-
olds at 11.5% (typ) below the nominal input voltage. For
example, the 5V typical threshold is 4.425V, or 75mV
below the ideal threshold of 4.500V. The guaranteed
threshold lies in the band between 4.500V and 4.350V
over temperature.
V
(V)
V
TRIP
(V)
R1 (kΩ)
2150
1780
1400
1300
1020
845
R2(kΩ)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
SUPPLY
12
11.25
9.4
10
8
7.5
7.5
6
7
5.6
5
4.725
3.055
2.82
1.5
3.3
3
511
1.0
464
2.5
1.8
1.5
1.2
1.0
0.9
0.8
0.7
0.6
2.325
1.685
1.410
1.120
0.933
0.840
0.750
0.655
0.561
365
0.5
237
0
182
–0.5
–1.0
–1.5
124
86.6
68.1
49.9
30.9
12.1
50
TEMPERATURE (°C)
75
–50
–25
0
25
100
29031 F04
Figure 4. LTC2903 Typical Threshold Accuracy vs Temperature
29031f a
11
LTC2903-1
W U U
U
APPLICATIO S I FOR ATIO
The powered system must work reliably down to the
lowest voltage in the threshold band or risk malfunction
before the reset line falls. In the 5V example, using the
1.5% accurate supervisor, the system ICs must work
downto4.35V.SystemICsworkingwitha±2.5%accurate
supervisor must operate down to 4.25V, increasing the
required system voltage margin and the probability of
system malfunction.
all inputs return above threshold. The nominal reset delay
time is 200ms. The counter clears whenever any input
drops back below threshold. This reset delay time effec-
tively provides further filtering of the voltage inputs. A
noisy input with frequency components of sufficient mag-
nitude above f = 1/tRST = 5Hz holds the reset line low,
preventing oscillatory behavior on the reset line.
Althoughallfourcomparatorshavebuilt-inglitchfiltering,
use bypass capacitors on the V1 and V2 inputs because
the greater of V1 or V2 supplies the VCC (options A1, B1
and C1) for the part (a 0.1µF ceramic capacitor satisfies
most applications). Apply filter capacitors on the V3 and
V4inputsinextremelynoisysituations. OptionsD1andE1
require a bypass capacitor only on V1. Apply filter capaci-
tors on V2, V3 and V4 adjustable inputs in extremely noisy
situations.
In any supervisory application, supply noise riding on the
monitored DC voltage can cause spurious resets, particu-
larly when the monitored voltage approaches the reset
threshold. A less than desirable but commonly used
techniqueusedtomitigatethisproblemaddshysteresisto
the input comparator. The amount of added hysteresis,
usually specified as a percentage of the trip threshold,
effectively degrades the advertised accuracy of the part.
To maintain high accuracy, the LTC2903-1 does not use
hysteresis.
Reset Output Rise and Fall Time Estimation
The reset output line contains a weak pull-up current
source to the V2 supply (V1 for options D1 and E1). Use
an external pull-up resistor when the output needs to pull
to another voltage and/or when the reset output needs a
faster rise time. The open-drain output allows for wired-
OR connections when more than one signal needs to pull
down on the reset line. Estimate output rise time for the
open-drain output without an external pull-up using:
To minimize spurious resets while maintaining threshold
accuracy, the LTC2903-1 employs two forms of noise
filtering. The first line of defense incorporates proprietary
tailoring of the comparator transient response. Transient
events receive electronic integration in the comparator
and must exceed a certain magnitude and duration to
cause the comparator to switch. Figure 5 illustrates the
typical transient duration versus comparator overdrive
(as a percentage of the trip threshold VRT) required to trip
the comparators. Once any comparator is switched, the
reset line pulls low. The reset time-out counter starts once
tRISE ≈ 2.2 • RPU • CLOAD
where RPU is the on-resistance of the pull-up transistor
and CLOAD is the external load capacitance on the pin. At
room temperature, the average RPU is approximately
50kΩ. When externally pulling up to voltages higher than
V2 (V1 for options D1 and E1), an internal network
automatically protects the weak pull-up circuitry from
reverse currents.
400
T
= 25°C
A
350
300
250
200
150
100
50
RESET OCCURS
ABOVE CURVE
The reset output has very strong pull-down capability.
Estimate the output fall time using:
tFALL ≈ 2.2 • RPD • CLOAD
where RPD is the on-resistance of the pull-down transistor
and CLOAD is the external load capacitance on the pin. At
roomtemperature,theaverageRPD isapproximately40Ω.
With a 150pF load capacitance the reset line can pull down
in about 13ns.
0
0.1
1
10
100
RESET COMPARATOR OVERDRIVE (% OF V
)
RTX
29031 F05
Figure 5. Typical Transient Duration vs Overdrive
Required to Trip Comparator
29031f a
12
LTC2903-1
U
TYPICAL APPLICATIO S
Quad Supply Monitor with Adjustable Input
1
2
3
6
5
4
3.3V
V1
RST
SYSTEM RESET
1V
C1
LTC2903-A1
R1
0.1µF
76.8k
GND
V2
V4
(V
= 0.884V)
R2
100k
TRIP
C2
0.1µF
2.5V
V3
1.8V
2903 TA02
Fixed Quad Supply Monitor with LED Indication on RST
5V
1k
LED
1
2
3
6
5
4
5V
V1
RST
SYSTEM RESET
1.8V
C1
LTC2903-B1
0.1µF
GND
V2
V4
C2
0.1µF
3.3V
V3
2.5V
2903 TA05
29031f a
13
LTC2903-1
TYPICAL APPLICATIO S
U
Quad Supply Monitor with Unused Input Pulled Above Threshold
1
2
3
6
5
4
5V
V1
RST
SYSTEM RESET
–5.2V
C1
LTC2903-C1
0.1µF
GND
V2
V4
C2
0.1µF
3.3V
V3
2903 TA03
Quad Supply Monitor with 3 Adjustable Inputs Monitoring
5% Supplies
1
2
6
5
3.3V
V1
RST
SYSTEM RESET
C1
LTC2903-D1
0.1µF
2150k
365k
GND
V2
V4
12V
(V
= 11.25V)
= 2.325V)
TRIP
100k
100k
237k
3
4
1.8V
= 1.685V)
V3
2.5V
(V
2903 TA06
(V
TRIP
TRIP
100k
29031f a
14
LTC2903-1
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
2.90 BSC
(NOTE 4)
0.62
MAX
0.95
REF
1.22 REF
1.4 MIN
1.50 – 1.75
2.80 BSC
3.85 MAX 2.62 REF
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.90 BSC
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 0302
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
29031f a
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LTC2903-1
U
TYPICAL APPLICATIO
Quad Supply Monitor with Manual Reset Button
3.3V
R3
10k
3.3V
V1
RST
SYSTEM RESET
12V
MANUAL
(V
= 10.75V)
TRIP
LTC2903-A1
RESET BUTTON
C1
0.1µF
R1
2050k
R
*
(NORMALLY OPEN)
ESD
10k
GND
V2
V4
R2
C2
0.1µF
100k
2.5V
V3
1.8V
2903 TA04
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC690
5V Supply Monitor, Watchdog Timer and Battery Backup
3.3V Supply Monitor, Watchdog Timer and Battery Backup
5V Supply Monitor and Watchdog Timer
4.65 Threshold
LTC694-3.3
LTC699
2.9V Threshold
4.65 Threshold
LTC1232
5V Supply Monitor, Watchdog Timer and Pushbutton Reset
4.37V/4.62V Threshold
4.725V, 3.118V, 1V Thresholds (±0.75%)
LTC1326
Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ
LTC1326-2.5
LTC1536
Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (±0.75%)
Precision Triple Supply Monitor for PCI Applications
Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ
Micropower Triple Supply Monitor for 5V, 3.3V and ADJ
Micropower Triple Supply Monitors with Open-Drain Reset
Meets PCI t
Timing Specifications
FAIL
LTC1726-2.5
LTC1726-5
LTC1727-2.5/LTC1727-5
Adjustable RESET and Watchdog Time Outs
Adjustable RESET and Watchdog Time Outs
Individual Monitor Outputs in MSOP
5-Lead SOT-23 Package
LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitors with Open-Drain Reset
LTC1728-2.5/LTC1728-5
LTC1985-1.8
Micropower Triple Supply Monitors with Open-Drain Reset
Micropower Triple Supply Monitor with Push-Pull Reset Output
Quad Voltage Monitor in MSOP
5-Lead SOT-23 Package
5-Lead SOT-23 Package
LTC2900
16 User Selectable Combinations,
±1.5% Threshold Accuracy
LTC2901
LTC2902
Quad Voltage Monitor with Watchdog
Quad Voltage Monitor with RST Disable
Precision Dual Supply Monitors
16 User Selectable Combinations, Adjustable Timers
16 User Selectable Combinations, Adjustable Tolerance
Pin Selectable Thresholds
LTC2904/LTC2905/
LTC2906/LTC2907
LTC2908
Precision Six Supply Monitor
8-Lead SOT-23 and DFN Packages
LTC2920-1/LTC2920-2
LTC2921/LTC2922
LTC2923
Single/Dual Power Supply Margining Controller
Power Supply Trackers with Input Monitors
Power Supply Tracking Controller
<0.4% Margin Voltage Precision
3 (LTC2921) and 5 (LTC2922) Remote Sense Switches
Tracks Up and Down, Supply Sequencing
29031f a
LT/TP 1004 1K • PRINTED IN THE USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
©LINEAR TECHNOLOGY CORPORATION 2003
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