LINER LTC2903-1 Precision quad supply monitor in 6-lead sot-23 Datasheet

LTC2903-1
Precision Quad Supply
Monitor in 6-Lead SOT-23
U
FEATURES
■
■
■
■
■
■
■
■
■
DESCRIPTIO
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)
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage over Temperature
10% Undervoltage Monitoring
Low Supply Current: 20µA Typical
200ms Reset Time Delay
Active Low Open-Drain RST Output
Power Supply Glitch Immunity
Low Profile (1mm) SOT-23 (ThinSOTTM) Package
U
APPLICATIO S
■
■
■
Internal supply voltage (VCC) is generated from the greater
voltage on the V1, V2 inputs. The RST output is guaranteed
to sink at least 5µA (VOL = 0.15V) for V1, V2 or V3 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. The LTC2903-1 is
available in a 6-lead low profile (1mm) SOT-23 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
Multivoltage Systems
Optical Networking Systems
Cell Phone Base Stations
Network Servers
U
■
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.
TYPICAL APPLICATIO
Low Voltage Reset Pull-Down Performance
vs External Pull-Up Current and Input Supply Voltage
0.10
5V
VIN = V1 = V2 = V3
0.09
SYSTEM
LOGIC
C1
0.1µF
C2
0.1µF
LTC2903-B1
RST
V1
GND
V4
V2
V3
0.08
RESET PIN VOLTAGE (V)
3.3V
DC/DC
2.5V
CONVERTER
1.8V
0.07
20µA
0.06
10µA
0.05
0.04
5µA
0.03
0.02
2903 TA01
0.01
0
2µA
1µA
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
VIN, INPUT SUPPLY VOLTAGE (V)
1
2903 TA01b
29031f
1
LTC2903-1
U
W
U
U
W W
W
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Notes 1, 2, 3)
V1, V2 ...................................................... – 0.3V to 6.5V
V3 ................................................. 2.7V or (VCC + 0.3V)
V4 (LTC2903-A1, LTC2903-B1) ................– 0.3V to 6.5V
V4 (LTC2903-C1) .................................... – 6.5V to 0.3V
RST ........................................................ – 0.3V to 6.5V
Operating Temperature Range
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
TOP VIEW
6 RST
V1 1
GND 2
5 V4
V2 3
4 V3
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
TJMAX = 125°C, θJA = 230°C/W
ORDER PART NUMBER
S6 PART MARKING
LTC2903CS6-A1
LTC2903CS6-B1
LTC2903CS6-C1
LTC2903IS6-A1
LTC2903IS6-B1
LTC2903IS6-C1
LTAFV
LTAJN
LTAJQ
LTAFW
LTAJP
LTAJR
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
UNITS
VRT33
3.3V, 10% Reset Threshold
V1 Input Threshold
●
2.871
2.921
2.970
V
VRT25
2.5V, 10% Reset Threshold
VRT18
1.8V, 10% Reset Threshold
V2 Input Threshold
●
2.175
2.213
2.250
V
V3 Input Threshold
●
1.566
1.593
1.620
V
VRTA
Adjustable Reset Threshold
V4 Input Threshold
●
0.492
0.500
0.508
V
(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
UNITS
VRT50
5V, 10% Reset Threshold
V1 Input Threshold
VRT33
3.3V, 10% Reset Threshold
V2 Input Threshold
●
4.350
4.425
4.500
V
●
2.871
2.921
2.970
V
VRT25
2.5V, 10% Reset Threshold
V3 Input Threshold
●
2.175
2.213
2.250
V
VRT18
1.8V, 10% Reset Threshold
V4 Input Threshold
●
1.566
1.593
1.620
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
UNITS
VRT50
5V, 10% Reset Threshold
V1 Input Threshold
●
4.350
4.425
4.500
V
VRT33
3.3V, 10% Reset Threshold
V2 Input Threshold
●
2.871
2.921
2.970
V
VRT18
1.8V, 10% Reset Threshold
V3 Input Threshold
●
1.566
1.593
1.620
V
VRT52N
–5.2V, 10% Reset Threshold
V4 Input Threshold
●
–4.524 –4.602 –4.680
V
29031f
2
LTC2903-1
ELECTRICAL CHARACTERISTICS
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
TYP
MAX
IV1
V1 Input Current (Note 4)
V1 = 3.3V (LTC2903-A1)
V1 = 5V (LTC2903-B1, LTC2903-C1)
●
●
MIN
20
25
80
80
µA
µA
IV2
V2 Input Current (Note 4)
V2 = 2.5V (LTC2903-A1)
V2 = 3.3V (LTC2903-B1, LTC2903-C1)
●
●
8
10
30
30
µA
µA
IV3
V3 Input Current
V3 = 1.8V (LTC2903-A1, LTC2903-C1)
V3 = 2.5V (LTC2903-B1)
●
●
6
8
30
30
µA
µA
IV4
V4 Input Current
V4 = 0.55V (LTC2903-A1)
V4 = 1.8V (LTC2903-B1)
V4 = –5.2V (LTC2903-C1)
●
●
●
2
–3
±15
4
–6
nA
µA
µA
200
260
ms
tRST
Reset Time-Out Period
tUV
VX Undervoltage Detect to RST
VOH
Output Voltage High RST (LTC2903-1) (Note 5)
IRST(DN) = –1µA
●
VOL
Output Voltage Low RST (Note 6)
VCC = 0.2V, IRST = 0.1µA
VCC = 0.5V, IRST = 5µA
VCC = 1V, IRST = 200µA
VCC = 3V, IRST = 2500µA
●
●
●
●
●
140
VX Less Than Threshold VRTX by
More Than 1%
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: All currents into pins are positive, all voltages are referenced to
GND unless otherwise noted.
Note 3: The internal supply voltage (VCC) is generated from the greater
voltage on the V1, V2 inputs.
Note 4: Under typical operating conditions, quiescent current is drawn
from the V1 input. When V2 exceeds V1, V2 supplies the quiescent
current.
UNITS
µs
150
V2 – 1
V
5
10
25
100
60
150
300
300
mV
mV
mV
mV
Note 5: The RST output pin on the LTC2903-1 has an internal pull-up to
V2 of typically 10µA. However, for faster rise times or for VOH voltages
greater than V2, use an external pull-up resistor.
Note 6: At input voltages below 1V on V1 and V2, voltage on V3 assists
pulling down the RST output.
29031f
3
LTC2903-1
U W
TYPICAL PERFOR A CE CHARACTERISTICS
5V Threshold Voltage
vs Temperature
3.3V Threshold Voltage
vs Temperature
2.975
4.475
4.450
4.425
4.400
4.375
4.350
–50
–25
75
0
25
50
TEMPERATURE (°C)
2.250
THRESHOLD VOLTAGE, VRT25 (V)
THRESHOLD VOLTAGE, VRT33 (V)
4.500
THRESHOLD VOLTAGE, VRT50 (V)
2.5V Threshold Voltage
vs Temperature
2.950
2.925
2.900
2.875
–50
100
75
0
25
50
TEMPERATURE (°C)
–25
28031 G01
1.595
1.585
1.575
75
0
25
50
TEMPERATURE (°C)
0.505
0.500
0.495
75
0
25
50
TEMPERATURE (°C)
–25
30
25
20
–4.605
–4.630
–4.655
–4.680
–50
10
30
25
V1 = 5V
V2 = 3.3V
V3 = 1.8V
V4 = –5.2V
IV1
IVX (µA)
IV1
15
15
10
IV2
5
IV2
IV3
5
IV3
0
IV3
IV4
IV4
0
25
50
TEMPERATURE (°C)
75
100
29031 G07
0
–50
100
20
10
–25
75
Supply Currents
vs Temperature (LTC2903C)
V1 = 5V
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
IV2
5
0
25
50
TEMPERATURE (°C)
–25
28031 G06
20
IVX (µA)
IVX (µA)
–4.580
Supply Currents
vs Temperature (LTC2903B)
V1 = 3.3V
V2 = 2.5V
V3 = 1.8V
0
–50
100
–4.555
28031 G05
Supply Currents
vs Temperature (LTC2903A)
100
–5.2V Threshold Voltage
vs Temperature
28031 G04
15
75
–4.530
0.490
–50
100
IV1
0
25
50
TEMPERATURE (°C)
–25
28031 G03
THRESHOLD VOLTAGE, VRT52N (V)
THRESHOLD VOLTAGE, VRTA (V)
THRESHOLD VOLTAGE, VRT18 (V)
1.605
25
2.190
2.175
–50
100
0.510
1.615
30
2.205
ADJ Threshold Voltage
vs Temperature
1.625
–25
2.220
28031 G02
1.8V Threshold Voltage
vs Temperature
1.565
–50
2.235
–25
0
25
50
TEMPERATURE (°C)
75
100
29031 G08
–5
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
29031 G09
29031f
4
LTC2903-1
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Reset Time-Out Period
vs Temperature
Transient Duration
vs Comparator Overdrive
260
350
300
250
RESET OCCURS
ABOVE CURVE
200
150
100
50
0
1
10
100
0.1
RESET COMPARATOR OVERDRIVE (% OF VRTX)
5.0
V1 = V2 = V3
LTC2903B, C
4.5
240
RST OUTPUT VOLTAGE (V)
RESET TIME-OUT PERIOD, tRST (ms)
400
TYPICAL TRANSIENT DURATION (µs)
RST Output Voltage with 10k
Pull-Up to V1
220
200
180
160
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
140
–50
–25
75
0
25
50
TEMPERATURE (°C)
29031 G10
0
100
0
0.5
1
1.5
2
2.5 3
V1 (V)
3.5
4
29301 G11
0.30
0.10
5
29031 G12
Low Voltage Reset Pull-Down
Performance vs External Pull-Up
Current and Input Supply Voltage
RST Output Voltage with
10k Pull-Up to V1
4.5
RST Current Sink Capability
vs VCC
15
VIN = V1 = V2 = V3
0.09
0.15
V1 ONLY
0.10
0.07
10µA
0.05
0.04
5µA
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
V1 (V)
1µA
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
VIN, INPUT SUPPLY VOLTAGE (V)
29301 G13
RST Voltage Output Low
vs RST Sink Current
1.5
1.2
85°C
0
0.5
1
1.5
2
2.5 3
VCC (V)
3.5
4
4.5
5
29031 G15
RST Voltage Output Low
vs RST Sink Current
1.5
LTC2903A
V1 = 3.3V
V2 = 2.1V
0
1
29031 G14
25°C
1.2
LTC2903B, C
V1 = 5V
V2 = 2.7V
25°C
–45°C
85°C
0.9
VOL (V)
0
VOL = 0.2V
6
3
2µA
0.01
V1 = V2 = V3
9
0.03
0.02
0.05
VOL = 0.4V
20µA
0.06
IRST (mA)
RESET PIN VOLTAGE (V)
0.20
0
12
0.08
VOL (V)
RST OUTPUT VOLTAGE (V)
0.25
0.6
0.6
0.3
0.3
0
–45°C
0.9
0
0
5
10
15
25 30
IRST (mA)
20
35
40
45
29031 G16
0
10
20
40
30
IRST (mA)
50
60
29031 G16
29031f
5
LTC2903-1
U W
TYPICAL PERFOR A CE CHARACTERISTICS
RST Pull-Up Current vs External
Pull-Down Voltage on RST
RST Pull-Up Current vs V2
–90
–40
V1, V3, V4 ABOVE THRESHOLD
–80
–35
–70
–30
LTC2903B, C
IRST (µA)
IRST (µA)
–60
–50
–40
–20
–15
–30
LTC2903A
–10
–20
VRT25
VRT33
–5
–10
0
–25
0
0
0.5
1
1.5
2
2.5 3
V2 (V)
3.5
4
4.5
5
0.5
0
28031 G18
1
2
1.5
VRST (V)
2.5
3
3.5
29031 G19
U
U
U
PI FU CTIO S
V1 (Pin 1): Voltage Input 1 (5V, 3.3V). Internal VCC is
generated from the greater voltage on the V1, V2 inputs.
Bypass this pin to ground with a 0.1µF (or greater)
capacitor.
V3 (Pin 4): Voltage Input 3 (2.5V, 1.8V). This input assists
the RST pull-down circuitry below 1V.
GND (Pin 2): Ground.
RST (Pin 6): Reset Logic Output. Pulls low when any voltage 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. Use an external pull-up for faster rise
times or output voltages greater than V2.
V2 (Pin 3): Voltage Input 2 (3.3V, 2.5V). Internal VCC is
generated from the greater voltage on the V1, V2 inputs.
Bypass this pin to ground with a 0.1µF (or greater)
capacitor.
V4 (Pin 5): Voltage Input 4 (ADJ, 1.8V, –5.2V). See Table
1 for recommended ADJ resistor values.
WU
W
TI I G DIAGRA
VX
VRTX
tUV
RST
tRST
1.5V
2903 TD
29031f
6
LTC2903-1
W
BLOCK DIAGRA S
V1 1
3.3V
(LTC2903-A1)
–
V1
+
POWER
DETECT
V2
VCC
V2
10µA
V2 3
2.5V
–
RESET DELAY GENERATOR
+
V3 4
1.8V
200ms
DELAY
–
V1
V2
V3
+
V4 5
ADJ
6 RST
LOW VOLTAGE
PULL-DOWN
–
+
GND 2
BANDGAP
REFERENCE
2903 BD1
29031f
7
LTC2903-1
W
BLOCK DIAGRA S
V1 1
5V
(LTC2903-B1)
–
V1
+
POWER
DETECT
V2
VCC
V2
10µA
V2 3
3.3V
–
RESET DELAY GENERATOR
+
V3 4
2.5V
200ms
DELAY
–
V1
V2
V3
+
V4 5
1.8V
6 RST
LOW VOLTAGE
PULL-DOWN
–
+
GND 2
BANDGAP
REFERENCE
2903 BD2
29031f
8
LTC2903-1
W
BLOCK DIAGRA S
V1 1
5V
(LTC2903-C1)
–
V1
+
POWER
DETECT
V2
VCC
V2
10µA
V2 3
3.3V
–
RESET DELAY GENERATOR
+
V3 4
1.8V
200ms
DELAY
–
V1
V2
V3
+
V4 5
–5.2V
6 RST
LOW VOLTAGE
PULL-DOWN
+
–
GND 2
BANDGAP
REFERENCE
2903 BD3
29031f
9
LTC2903-1
U
W
U U
APPLICATIO S I FOR ATIO
Power-Up
Supply Monitoring
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, V2 or V3. The pull-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.
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 during power-up, power-down and brownout conditions on
any of the voltage inputs.
For applications requiring an adjustable trip threshold, use
the V4 input on the LTC2903-A1. Connect the tap point on
an external resistive divider (R1, R2) placed between the
positive voltage being sensed and ground, to the high
impedance input on V4. The LTC2903-A1 compares the
voltage on the V4 pin to the internal 0.5V reference.
Figure␣ 3 shows a generic setup for the positive adjustable
application.
0.7
When V1, V2 and V3 are ramped simultaneously, 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 current sinking ability for single
supply and triple supply-tracking applications. Figure 2
shows a detailed view of the reset pin voltage with a 10k
pull-up resistor to V1.
RST OUTPUT VOLTAGE (V)
0.6
The LTC2903-1 supervisors derive their internal supply
voltage (VCC) automatically from the greater voltage on the
V1 and V2 inputs. With all supply inputs above threshold,
the quiescent current drawn from VCC is 20µA (typ).
10000
TA = 25°C
VRST = 0.3VCC
TA = 25°C
0.5
0.4
COMPETITION
PART
0.3
0.2
V1 ONLY
V1 = V2 = V3
0.1
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
V1 (V)
39031 F02
Figure 2. RST Output Voltage with a 10k Pull-Up to V1
(Enlarged Area of Detail)
IRST (µA)
1000
V1 = V2 = V3
100
VTRIP
V1 ONLY
R1
1%
LTC2903-A1
–
V4
R2
1%
10
+
0.5V
1
0
0.2
0.4
0.6
VCC (V)
0.8
1.0
+
–
1.2
29031 F01
Figure 1. RST Pull-Down Current vs VCC
29031 F03
Figure 3. Setting the Positive Adjustable Trip Point
29031f
10
LTC2903-1
U
W
U U
APPLICATIO S I FOR ATIO
supervisor does not exist—the actual reset threshold may
vary over a specified band (±1.5% for the LTC2903-1 supervisors). Figure 4 shows the typical relative threshold
accuracy for all four inputs, over temperature.
 R1
VTRIP = 0.5V 1 + 
 R2 
Table 1 contains suggested 1% resistor values for the ADJ
input to obtain nominal –11.5% thresholds.
Table 1. Suggested 1% Resistor Values for the ADJ Input
VSUPPLY (V)
VTRIP (V)
R1 (kΩ)
R2(kΩ)
12
10.75
2050
100
10
8.95
1690
100
8
7.15
1330
100
7.5
6.7
1240
100
6
5.38
976
100
5
4.435
787
100
3.3
2.935
487
100
3
2.66
432
100
2.5
2.2
340
100
1.8
1.605
221
100
1.5
1.325
165
100
1.2
1.065
113
100
1
0.884
76.8
100
0.9
0.795
59
100
Connect unused supervisor inputs to the highest supply
voltage available (typically V1). On the LTC2903-C1, the
negative V4 input must always be applied.
Implications of Threshold Accuracy
Specifying system voltage margin for worst-case operation requires consideration of three factors: power supply
tolerance, IC supply voltage tolerance and supervisor reset 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
With this variation of reset threshold in mind, the nominal
reset threshold of the supervisor resides below the minimum supply voltage; just enough so that the reset threshold 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).
Adding half of the reset threshold accuracy spread (1.5%)
to the ideal 10% thresholds puts the LTC2903-1 thresholds 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.
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
down to 4.35V. System ICs working with a ±2.5% accurate
supervisor must operate down to 4.25V, increasing the
required system voltage margin and the probability of
system malfunction.
1.5
TYPICAL THRESHOLD ACCURACY (%)
Calculate the trip voltage from:
1.0
0.5
0
–0.5
–1.0
–1.5
–50
–25
50
0
25
TEMPERATURE (°C)
75
100
29031 F04
Figure 4. LTC2903 Typical Threshold Accuracy vs Temperature
29031f
11
LTC2903-1
U
W
U U
APPLICATIO S I FOR ATIO
In any supervisory application, supply noise riding on the
monitored DC voltage can cause spurious resets, particularly when the monitored voltage approaches the reset
threshold. A less than desirable but commonly used
technique used to mitigate this problem adds hysteresis to
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.
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
all inputs return above threshold. The nominal reset delay
time is 200ms. The counter clears whenever any input
TYPICAL TRANSIENT DURATION (µs)
400
Although all four comparators have built-in glitch filtering,
use bypass capacitors on the V1 and V2 inputs because
the greater of V1 or V2 supplies the VCC for the part (a
0.1µF ceramic capacitor satisfies most applications). Apply filter capacitors on the V3 and V4 inputs in extremely
noisy situations.
Reset Output Rise and Fall Time Estimation
The reset output line contains a weak pull-up current
source to the V2 supply. 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 opendrain 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:
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, an internal network automatically protects the weak
pull-up circuitry from reverse currents.
TA = 25°C
350
300
250
200
drops back below threshold. This reset delay time effectively provides further filtering of the voltage inputs. A
noisy input with frequency components of sufficient magnitude above f = 1/tRST = 5Hz holds the reset line low,
preventing oscillatory behavior on the reset line.
RESET OCCURS
ABOVE CURVE
The reset output has very strong pull-down capability.
Estimate the output fall time using:
150
100
tFALL ≈ 2.2 • RPD • CLOAD
50
0
1
10
100
0.1
RESET COMPARATOR OVERDRIVE (% OF VRTX)
29031 F05
Figure 5. Typical Transient Duration vs Overdrive
Required to Trip Comparator
where RPD is the on-resistance of the pull-down transistor
and CLOAD is the external load capacitance on the pin. At
room temperature, the average RPD is approximately 40Ω.
With a 150pF load capacitance the reset line can pull down
in about 13ns.
29031f
12
LTC2903-1
U
TYPICAL APPLICATIO S
Quad Supply Monitor with Adjustable Input
1
3.3V
C1
0.1µF
V1
RST
6
LTC2903-A1
2
GND
V4
R1
76.8k
5
1V
R2
100k
C2
0.1µF
3
2.5V
SYSTEM RESET
V2
V3
4
1.8V
2903 TA02
Fixed Quad Supply Monitor with LED Indication on RST
5V
1k
LED
1
5V
C1
0.1µF
V1
RST
6
SYSTEM RESET
LTC2903-B1
2
GND
V4
V2
V3
5
1.8V
C2
0.1µF
3.3V
3
4
2.5V
2903 TA05
29031f
13
LTC2903-1
U
TYPICAL APPLICATIO S
Quad Supply Monitor with Unused Input Pulled Above Threshold
1
5V
C1
0.1µF
V1
RST
6
SYSTEM RESET
LTC2903-C1
2
GND
V4
V2
V3
5
–5.2V
C2
0.1µF
3.3V
3
4
2903 TA03
29031f
14
LTC2903-1
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
0.62
MAX
2.90 BSC
(NOTE 4)
0.95
REF
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 – 1.75
(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
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
(NOTE 3)
1.90 BSC
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
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC2903-1
U
TYPICAL APPLICATIO
Quad Supply Monitor with Manual Reset Button
3.3V
1
3.3V
V1
RST
2
GND
V4
MANUAL
RESET BUTTON
R1
RESD* (NORMALLY OPEN)
2050k 10k
5
R2
100k
C2
0.1µF
3
2.5V
SYSTEM RESET
12V
(VTRIP = 10.75V)
LTC2903-A1
C1
0.1µF
R3
10k
6
V2
V3
4
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
4.65 Threshold
LTC694-3.3
3.3V Supply Monitor, Watchdog Timer and Battery Backup
2.9V Threshold
LTC699
5V Supply Monitor and Watchdog Timer
4.65 Threshold
LTC1232
5V Supply Monitor, Watchdog Timer and Pushbutton Reset
4.37V/4.62V Threshold
LTC1326
Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ
4.725V, 3.118V, 1V Thresholds (±0.75%)
LTC1326-2.5
Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (±0.75%)
LTC1536
Precision triple Supply Monitor for PCI Applications
Meets PCI tFAIL Timing Specifications
LTC1726-2.5
Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ
Adjustable RESET and Watchdog Time Outs
LTC1726-5
Micropower Triple Supply Monitor for 5V, 3.3V and ADJ
Adjustable RESET and Watchdog Time Outs
LTC1727-2.5/LTC1727-5
Micropower Triple Supply Monitors with Open-Drain Reset
Individual Monitor Outputs in MSOP
LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitors with Open-Drain Reset
5-Lead SOT-23 Package
LTC1728-2.5/LTC1728-5
Micropower Triple Supply Monitors with Open-Drain Reset
5-Lead SOT-23 Package
LTC1985-1.8
Micropower Triple Supply Monitor with Push-Pull Reset Output
5-Lead SOT-23 Package
LTC2900
Quad Voltage Monitor in MSOP
16 User Selectable Combinations,
±1.5% Threshold Accuracy
LTC2901
Quad Voltage Monitor with Watchdog
16 User Selectable Combinations, Adjustable Timers
LTC2902
Quad Voltage Monitor with RST Disable
16 User Selectable Combinations, Adjustable Tolerance
LTC2920-1/LTC2920-2
Single/Dual Power Supply Margining Controller
<0.4% Margin Voltage Precision
LTC2921/LTC2922
Power Supply Trackers with Input Monitors
3 (LTC2921) and 5 (LTC2922) Remote Sense Switches
LTC2923
Power Supply Tracking Controller
Tracks Up and Down, Supply Sequencing
29031f
16
Linear Technology Corporation
LT/TP 1203 1K • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2003