LTC2905CDDBTRMPBF [Linear]
Precision Dual Supply Monitors with Pin-Selectable Thresholds; 精密双电源监视器与引脚可选门限
| 型号： | LTC2905CDDBTRMPBF |
| 厂家： | 
Linear |
| 描述： | Precision Dual Supply Monitors with Pin-Selectable Thresholds |
| 文件： | 总16页 (文件大小：151K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC2904/LTC2905
Precision Dual Supply
Monitors with Pin-Selectable
Thresholds
FEATURES
DESCRIPTION
The LTC®2904/LTC2905 are dual supply monitors in-
tended for systems with two supply voltages. The dual
supply monitors have a common reset output with delay
(200ms for the LTC2904 and adjustable using an exter-
nal capacitor for the LTC2905). This product provides a
precise, space-conscious and micropower solution for
supply monitoring.
n
Monitors Two Inputs Simultaneously
n
Nine Threshold Combinations
n
Three Supply Tolerances (5%, 7.5%, 10%)
n
Guaranteed Threshold Accuracy: 1.5% of
Monitored Voltage Over Temperature
n
Internal V Auto Select
CC
n
Power Supply Glitch Immunity
n
200ms Reset Time Delay (LTC2904 Only)
The LTC2904/LTC2905 feature a tight 1.5% threshold
accuracyoverthewholeoperatingtemperaturerange,and
glitch immunity to ensure reliable reset operation without
false triggering. The open drain RST output is guaranteed
to be in the correct state for inputs down to 1V.
n
Adjustable Reset Time Delay (LTC2905 Only)
n
Open Drain RST Output
n
Guaranteed RST for V1 ≥ 1V or V2 ≥ 1V
n
Low Profile (1mm) SOT-23 (ThinSOT™) and
Plastic (3mm × 2mm) DFN Packages
The LTC2904/LTC2905 also feature three programming
inputpins,whichprogramthethresholdandtolerancelevel
without requiring any external components. These three
programming pins provide a total of 27 different voltage
level and tolerance combinations, eliminating the need to
have different parts for development and implementation
of different systems with different voltage levels requiring
monitoring function.
APPLICATIONS
n
Desktop and Notebook Computers
n
Handheld Devices
n
Network Servers
n
Core, I/O Monitor
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
5V, 3.3V Dual Supply Monitor with 5% Tolerance
Table 1. Voltage Threshold Programming
V1
5.0
3.3
3.3
3.3
3.3
2.5
2.5
2.5
2.5
V2
3.3
2.5
1.8
1.5
1.2
1.8
1.5
1.2
1.0
S1
V1
S2
V1
5V
DC/DC
SYSTEM
LOGIC
3.3V
CONVERTER
Open
V1
GND
Open
V1
V1
V2
TMR
GND
RST
LTC2905
0.1μF
0.1μF
22nF
Open
Open
GND
GND
GND
V1
S1
Open
GND
Open
V1
S2
TOL
29045 TA01
GND
29045fd
1
LTC2904/LTC2905
ABSOLUTE MAXIMUM RATINGS (Note 1, 2)
Terminal Voltages
Operating Temperature Range
V1, V2...................................................... –0.3V to 7V
LTC2904C/LTC2905C .............................. 0°C to 70°C
LTC2904I/LTC2905I.............................–40°C to 85°C
LTC2905H.......................................... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
TSOT Lead Temperature (Soldering, 10 sec).........300°C
S1, S2, TOL................................–0.3V to (V +0.3V)
CC
RST.......................................................... –0.3V to 7V
RST (LTC2904)........................................ –0.3V to 7V
TMR (LTC2905)....................................... –0.3V to 7V
PIN CONFIGURATION
TOP VIEW
TOP VIEW
GND
RST
1
2
3
4
8
7
6
5
TOL
S1
V2 1
RST/TMR* 2
RST 3
8 V1
7 S2
6 S1
5 TOL
9
RST/TMR*
V2
S2
V1
GND 4
TS8 PACKAGE
DDB8 PACKAGE
8-LEAD PLASTIC TSOT-23
8-LEAD (3mm s 2mm) PLASTIC DFN
EXPOSED PAD IS GND (PIN 9),
MUST BE SOLDERED TO PCB
* RST FOR LTC2904
* RST FOR LTC2904
TMR FOR LTC2905
T
= 150°C, θ = 195°C/W
JA
JMAX
TMR FOR LTC2905
T
JMAX
= 150°C, θ = 76°C/W
JA
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
LTC2904CDDB#TRMPBF
LTC2904IDDB#TRMPBF
LTC2905CDDB#TRMPBF
LTC2905HDDB#TRMPBF
LTC2905IDDB#TRMPBF
LTC2904CTS8#TRMPBF
LTC2904ITS8#TRMPBF
LTC2905CTS8#TRMPBF
LTC2905HTS8#TRMPBF
LTC2905ITS8#TRMPBF
TAPE AND REEL
PART MARKING*
LBCZ
PACKAGE DESCRIPTION
TEMPERATURE RANGE
0°C to 70°C
LTC2904CDDB#TRPBF
LTC2904IDDB#TRPBF
LTC2905CDDB#TRPBF
LTC2905HDDB#TRPBF
LTC2905IDDB#TRPBF
LTC2904CTS8#TRPBF
LTC2904ITS8#TRPBF
LTC2905CTS8#TRPBF
LTC2905HTS8#TRPBF
LTC2905ITS8#TRPBF
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead Plastic TSOT-23
LBDB
–40°C to 85°C
0°C to 70°C
LAJF
LBCY
–40°C to 125°C
–40°C to 85°C
0°C to 70°C
LBCY
LTBCJ
LTBCK
LTAJD
8-Lead Plastic TSOT-23
–40°C to 85°C
0°C to 70°C
8-Lead Plastic TSOT-23
LTAJE
8-Lead Plastic TSOT-23
–40°C to 125°C
–40°C to 85°C
LTAJE
8-Lead Plastic TSOT-23
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/
29045fd
2
LTC2904/LTC2905
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V1 = 2.5V, V2 = 1V, S1 = TOL = V1, S2 = 0V, unless otherwise noted.
(Notes 2, 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
l
V
V
V
V
V
V
V
V
5V, 5% Reset Threshold
5V, 7.5% Reset Threshold
5V, 10% Reset Threshold
3.3V, 5% Reset Threshold
3.3V, 7.5% Reset Threshold
3.3V, 10% Reset Threshold
2.5V, 5% Reset Threshold
2.5V, 7.5% Reset Threshold
2.5V, 10% Reset Threshold
1.8V, 5% Reset Threshold
1.8V, 7.5% Reset Threshold
1.8V, 10% Reset Threshold
1.5V, 5% Reset Threshold
1.5V, 7.5% Reset Threshold
1.5V, 10% Reset Threshold
1.2V, 5% Reset Threshold
1.2V, 7.5% Reset Threshold
1.2V, 10% Reset Threshold
1V, 5% Reset Threshold
1V, 7.5% Reset Threshold
1V, 10% Reset Threshold
V1 Input Threshold
4.600
4.475
4.350
3.036
2.954
2.871
2.300
2.238
2.175
1.656
1.611
1.566
1.380
1.343
1.305
1.104
1.074
1.044
0.920
0.895
0.870
4.675
4.550
4.425
3.086
3.003
2.921
2.338
2.275
2.213
1.683
1.638
1.593
1.403
1.365
1.328
1.122
1.092
1.062
0.935
0.910
0.885
4.750
4.625
4.500
3.135
3.053
2.970
2.375
2.313
2.250
1.710
1.665
1.620
1.425
1.388
1.350
1.140
1.110
1.080
0.950
0.925
0.900
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
μA
μA
RT50
RT33
RT25
RT18
RT15
RT12
RT10
CCMIN
l
l
l
V1, V2 Input Threshold
V1, V2 Input Threshold
V2 Input Threshold
V2 Input Threshold
V2 Input Threshold
V2 Input Threshold
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
Minimum Internal Operating Voltage (Note 2) RST in Correct Logic State
V1 Input Current
V2 Input Current
1
130
1.0
I
I
Includes Input Current to Three-State Pins
65
0.4
V1
V2
l
I
I
TMR Pull-Up Current
TMR Pull-Down Current
LTC2905
LTC2905
LTC2905H
V
= 0V
= 1.4V
–1.5
1.5
1.4
–2.1
2.1
2.0
–2.7
2.7
2.7
μA
μA
μA
TMR(UP)
TMR
l
l
V
TMR
TMR(DOWN)
l
t
t
Reset Timeout Period
Reset Timeout Period
LTC2904
140
200
260
ms
RST
l
l
LTC2905
LTC2905H
C
= 22nF
140
140
200
260
295
ms
ms
RST
TMR
t
Vx Undervoltage Detect to
RST or RST
Vx Less than Reset Threshold V
by More than 1%
150
μs
UV
RTX
l
l
V
OL
V
OH
Output Voltage Low RST, RST
I = 2.5mA
0.15
0.05
0.4
0.3
V
V
V
I = 100μA; V1 = 1V (RST Only)
l
Output Voltage High RST, RST
(Notes 2, 5)
I = –1μA
V
–1
CC
Three-State Inputs S1, S2, TOL
l
l
l
V
V
V
Low Level Input Voltage
High Level Input Voltage
Pin Voltage When Left in Open State
0.4
1.1
V
V
V
V
V
V
V
V
IL
IH
Z
1.4
0.7
I = –10μA
I = 0μA
0.9
0.9
l
l
I = 10μA
2905H
I = –10μA
I = 0μA
I = 10μA
0.65
l
l
1.15
25
I
Programming Input Current (Note 6)
μA
VPG
29045fd
3
LTC2904/LTC2905
ELECTRICAL CHARACTERISTICS
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 5: The output pins RST and RST have an internal pull-up to V of
typically –6μA. However, an external pull-up resistor may be used when
CC
faster rise time is required or for V voltages greater than V
.
CC
OH
Note 6: The input current to the three-state input pins are the pull-up
and the pull-down current when the pins are either set to V1 or GND
respectively. In the open state, the maximum leakage current to V1 or GND
permissible is 10μA.
Note 2: The greater of V1, V2 is the internal supply voltage (V ).
CC
Note 3: All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 4: For reset thresholds test conditions refer to the voltage threshold
programming table in the Applications Information section.
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are at TA = 25°C unless otherwise noted.
5V Threshold Voltage
vs Temperature
3.3V Threshold Voltage
vs Temperature
2.5V Threshold Voltage
vs Temperature
4.75
4.70
4.65
4.60
4.55
4.50
4.45
4.40
4.35
3.120
3.070
3.020
2.970
2.920
2.870
2.375
2.325
2.275
2.225
2.175
5%
5%
5%
7.5%
7.5%
10%
7.5%
10%
10%
25
50
–50
–25
0
75
100
25
50
25
50
–50
–25
0
75
100
–50
–25
0
75
100
TEMPERATURE (oC)
TEMPERATURE (oC)
TEMPERATURE (oC)
29045 G01
29045 G02
29045 G03
1.8V Threshold Voltage
vs Temperature
1.5V Threshold Voltage
vs Temperature
1.2V Threshold Voltage
vs Temperature
1.705
1.685
1.665
1.645
1.625
1.605
1.585
1.565
1.135
1.125
1.115
1.105
1.095
1.085
1.075
1.065
1.055
1.045
1.425
1.405
1.385
1.365
1.345
1.325
1.305
5%
5%
5%
7.5%
7.5%
10%
7.5%
10%
10%
25
50
25
50
25
50
–50
–25
0
75
100
–50
–25
0
75
100
–50
–25
0
75
100
TEMPERATURE (oC)
TEMPERATURE (oC)
TEMPERATURE (oC)
29045 G04
29045 G05
29045 G06
29045fd
4
LTC2904/LTC2905
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are at TA = 25°C unless otherwise noted.
1V Threshold Voltage
vs Temperature
IV1 vs Temperature
IV2 vs Temperature
21.5
21.0
20.5
20.0
19.5
19.0
0.950
0.940
0.930
0.920
0.910
0.900
0.890
0.880
0.870
1.8
V1 = 5V
V1 = 5V
V2 = 3.3V
V2 = 3.3V
5%
S1 S2
=
S1 S2
= = TOL = 1.4V
= TOL = 1.4V
1.7
1.6
1.5
1.4
1.3
1.2
7.5%
10%
25
50
25
50
25
50
–50
–25
0
75
100
–50
–25
0
75
100
–50
–25
0
75
100
TEMPERATURE (oC)
TEMPERATURE (oC)
TEMPERATURE (oC)
29045 G07
29045 G08
29045 G09
Typical Transient Duration
vs Comparator Overdrive (V1, V2)
Reset Time Out Period (tRST
)
IV2 vs Temperature
vs Capacitance (CTMR
)
700
600
500
400
300
200
100
0
10000
1000
100
10
20.0
19.5
19.0
18.5
18.0
17.5
17.0
V1 = 2.5V
V2 = 3.3V
S1 = S2 = TOL = 1.4V
RESET OCCURS
ABOVE CURVE
1
0.1
0.1
1
10
100
25
50
–50
–25
0
75
100
10p
100p
1n
10n
(FARAD)
100n
1M
COMPARATOR OVERDRIVE VOLTAGE (% OF V
)
C
TEMPERATURE (oC)
RTX
TMR
29045 G12
29045 G11
29045 G10
Reset Timeout Period (tRST
)
vs Temperature
RST Output Voltage vs V1
RST Output Voltage vs V1
5
4
5
4
235
230
225
220
215
210
205
200
195
CRT = 22nF
(FILM)
V2 = S1 = S2 = TOL = V1
10k PULL-UP RESISTOR
V2 = S1 = S2 = TOL = V1
10k PULL-UP RESISTOR
3
3
2
2
1
1
0
0
–1
–1
25
50
–50
–25
0
75
100
0
1
2
3
4
5
0
1
2
3
4
5
V1 (V)
V1 (V)
TEMPERATURE (oC)
29045 G13
29045 G15
29045 G14
29045fd
5
LTC2904/LTC2905
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are at TA = 25°C unless otherwise noted.
RST Pull-Down Current (IRST
)
RST Pull-Down Current (IRST
)
RST Output Voltage vs V1
vs Supply Voltage (VCC
)
vs Supply Voltage (VCC
)
5
4
S1
= V2 = V1
TOL = S2 = GND
NO PULL-UP R
V2 = S1 = S2 = TOL = V1
10pF CAPACITOR AT RST
V2 = S1 = S2 = TOL = V1
NO PULL-UP R
5
4
3
2
1
0
5
4
3
2
1
0
3
RST AT 150mV
RST AT 50mV
RST AT 150mV
2
1
RST AT 50mV
0
–1
0
1
2
3
4
5
0
1
2
3
4
5
0
1
2
3
4
5
V1 (V)
SUPPLY VOLTAGE, V (V)
SUPPLY VOLTAGE, V (V)
CC
CC
29045 G16
29045 G17
29045 G18
RST Output Voltage Low (VOL
)
RST Output Voltage Low (VOL
)
RST Pull-Up Current (IRST
)
vs RST Pull-Down Current (IRST
)
vs RST Pull-Down Current (IRST
)
vs Supply Voltage (VCC
)
–18
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
TOL = GND
V1 = 5V
V1 = 5V
25oC
–16
–14
–12
–10
–8
V2 = 3V
S1 = S2 = TOL = V1
NO PULL-UP R
V2 = 3.3V
85oC
25oC
85oC
S1 = S2 = TOL = V1
NO PULL-UP R
–40oC
–40oC
–6
–4
–2
V
V
V
RT50
RT25
2.5
RT33
0
2.0
3.0
3.5
5.0
4.0
4.5
0
10
30
40
50
(mA)
60
0
10
30
40
50
(mA)
60
20
20
SUPPLY VOLTAGE, V (V)
RST PULL-DOWN CURRENT, I
RST PULL-DOWN CURRENT, I
CC
RST
RST
29045 G21
29045 G19
29045 G20
RST Pull-Up Current (IRST
)
RST Output Voltage High (VOH
)
RST Output Voltage High (VOH)
vs RST Output Source Current (IRST)
vs Supply Voltage (VCC
)
vs RST Output Source Current (IRST
)
3.0
2.5
2.0
1.5
1.0
0.5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
–16
–14
–12
–10
–8
V1 = 3.3V
V1 = 3.3V
TOL = V1
V2 = 1.8V
V2 = 1.5V
S1 = TOL =V1
S2 = OPEN
NO PULL-UP R
S1 = TOL = V1
S2 = OPEN
NO PULL-UP R
–40oC
85oC
–6
85oC
–4
–40oC
25oC
25oC
–2
V
V
V
RT25
RT33
RT50
0
2.0
2.5
3.0
3.5
5.0
–12
–8
–6
–4
–2
(MA)
0
–8 –7 –6 –5 –4 –3 –2
OUTPUT SOURCE CURRENT, I
0
4.0
4.5
–10
–1
(MA)
OUTPUT SOURCE CURRENT, I
SUPPLY VOLTAGE, V (V)
CC
RST
RST
29045 G22
29045 G23
29045 G24
29045fd
6
LTC2904/LTC2905
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are at TA = 25°C unless otherwise noted.
IS1, IS2, ITOL vs Temperature
IS1, IS2, ITOL vs Temperature
–20
–19
–18
–17
–16
–15
–14
–13
–12
–11
–10
20
19
18
17
16
15
14
13
12
11
10
S1 = S2 = TOL = GND
S1 = S2 = TOL = 3.3V
25
50
–50
–25
0
75
100
25
50
–50
–25
0
75
100
TEMPERATURE (oC)
TEMPERATURE (oC)
29045 G26
29045 G25
PIN FUNCTIONS (TS8/DDB8)
V2 (Pin 1/Pin 4): Voltage Input 2. Input for V2 monitor.
Select from 3.3V, 2.5V, 1.8V, 1.5V, 1.2V or 1.0V. Refer to
Table 1 for details. The greater of V1, V2 is also the internal
are above threshold. This pin has a weak pull-up to V
CC
and may be pulled above V using an external pull-up.
CC
GND (Pin 4/Pin 1, Pin 9): Ground.
supplyvoltage,V .Bypassthispintogroundwitha0.1μF
CC
TOL (Pin 5/Pin 8): Three-state Input for Supply Tolerance
Selection (5%, 7.5% or 10%). See the Applications Infor-
mation section for tolerance selection chart (Table 2).
(or greater) capacitor.
RST (Pin 2/Pin 3): (LTC2904 Only) Reset Logic Output.
When all voltage inputs are above the reset threshold for
atleasttheprogrammeddelaytime, thispinpullslow. This
S1 (Pin 6/Pin 7): Voltage Threshold Select Three-State
Input. Connect to V1, GND or leave unconnected in open
state (See Table 1).
pin has a weak pull-up to V and may be pulled above
CC
V
CC
using an external pull-up.
S2 (Pin 7/Pin 6): The Second Voltage Threshold Select
Three-State Input. Connect to V1, GND or leave uncon-
nected in open state (See Table 1).
TMR (Pin 2/Pin 3): (LTC2905 Only) Reset Delay Time
Programming Pin. Attach an external capacitor (C ) to
GND to set a reset delay time of 9ms/nF. Leaving the pin
opengeneratesaminimumdelayofapproximately200μs.A
22nF capacitor will generate a 200ms reset delay time.
TMR
V1 (Pin 8/Pin 5): Voltage Input 1. Input for V1 monitor.
Select from 5V, 3.3V, or 2.5V. See Table 1 for details.
The greater of V1, V2 is also the internal supply voltage,
RST (Pin 3/Pin 2): Inverted Reset Logic Output. Pulls low
when any voltage input is below the reset threshold and is
heldlowforprogrammeddelaytimeafterallvoltageinputs
V . Bypass this pin to ground with a 0.1μF (or greater)
CC
capacitor.
29045fd
7
LTC2904/LTC2905
BLOCK DIAGRAM
V
LTC2904
CC
6μA
–
+
RST
V1
V
CC
200ms
RESET PULSE
GENERATOR
POWER
DETECT
RESISTOR
NETWORK
V
CC
6μA
–
+
V2
RST
BAND GAP
REFERENCE
THREE-STATE DECODER
GND
2904 BD
S1
S2
TOL
LTC2905
–
+
TMR
RST
GND
V
CC
V1
V2
V
CC
6μA
POWER
DETECT
RESISTOR
NETWORK
RESET PULSE
GENERATOR
–
+
BAND GAP
REFERENCE
THREE-STATE DECODER
2905 BD
S1
S2
TOL
29045fd
8
LTC2904/LTC2905
TIMING DIAGRAM
VX Monitor Timing
V
RTX
V
X
t
t
UV
RST
RST
1V
1V
RST
29045 TD
APPLICATIONS INFORMATION
Supply Monitoring
Power-Up
The greater of V1, V2 is the internal supply voltage (V ).
The LTC2904/LTC2905 are low power, high accuracy dual
supplymonitorswithacommonresetoutputandselectable
thresholds. Reset delay is set to a nominal of 200ms for
the LTC2904 and is adjustable using an external capacitor
for the LTC2905.
CC
V
powers the drive circuits for the RST pin. Therefore as
CC
soon as V1 or V2 reaches 1V during power-up, the RST
output asserts low.
V
also powers the drive circuits for the RST pin in the
CC
The two 3-state input pins (S1 and S2) select one of nine
possible threshold voltage combinations. Another three-
state input pin sets the supply tolerance (5%, 7.5% or
10%). Both input voltages (V1 and V2) must be above
predetermined thresholds for the reset not to be invoked.
The LTC2904/LTC2905 assert the reset outputs during
power-up,power-downandbrownoutconditionsoneither
of the voltage inputs.
LTC2904. Therefore, RST weakly pulls high when V1 or
V2 reaches at least 1V.
Threshold programming is complete when V1 reaches
at least 2.17V. After programming, if either V1 or V2 falls
below its programmed threshold, RST asserts low (RST
weakly pulls high) as long as V is at least 1V.
CC
Once V1 and V2 rise above their thresholds, an internal
timer is started. After the programmed delay time, RST
weakly pulls high (RST asserts low).
29045fd
9
LTC2904/LTC2905
APPLICATIONS INFORMATION
Power-Down
Tolerance Programming
On power-down, once either V1 or V2 inputs drops below
The three-state input pin, TOL programs the common
supply tolerance for both V1 and V2 input voltages (5%,
7.5% or 10%). The larger the tolerance the lower the trip
threshold. Table 2 shows the tolerances selection corre-
sponding to a particular connection at the TOL pin.
its threshold, RST asserts logic low and RST weakly pulls
high. V of at least 1V guarantees a logic low of 0.4V at
CC
RST.
Programming Pins
Table 2. Tolerance Programming
The three 3-state input pins: S1, S2 and TOL should be
connected to GND, V1 or left unconnected during normal
operation. Notethatwhenleftunconnected, themaximum
leakage current allowable from the pin to either GND or
V1 is 10μA.
Tolerance
5%
TOL
V1
7.5%
Open
GND
10%
Threshold Accuracy
In margining applications, all the 3-state input pins can be
driven using a tri-state buffer. Note however the low and
Reset threshold accuracy is of the utmost importance in a
supply sensitive system. Ideally such a system should not
reset while supply voltages are within a specified margin
belowtheratednominallevel.BothoftheLTC2904/LTC2905
inputs have the same relative threshold accuracy. The
specification for LTC2904/LTC2905 is 1.5% of the pro-
grammed nominal input voltage (over the full operating
temperature range).
high output of the tri-state buffer has to satisfy the V and
IL
V of the 3-state pin listed in the Electrical Characteristics
IH
Table. Moreover, when the tri-state buffer is in the high
impedance state, the maximum leakage current allowed
from the pin to either GND or V1 is 10μA.
Monitor Programming
Connecting S1 and S2 to GND, V1 or leaving them open
selects the LTC2904/LTC2905 input voltage combina-
tions. Table 1 shows the nine possible combinations of
nominal input voltages and their corresponding S1, S2
connections.
Forexample,whentheLTC2904/LTC2905areprogrammed
to handle a 5V input with 10% tolerance (S1 = S2 = V1 and
TOL = GND, refer to Table 1 and Table 2), it does not issue
a reset command when V1 is above 4.5V. The typical 10%
trip threshold is at 11.5% below the nominal input voltage
level. Therefore, the typical trip threshold for the 5V input
is4.425V. With 1.5%accuracy, thetripthresholdrangeis
4.425V 75mV over temperature (i.e. 10% to 13% below
5V). This implies that the monitored system must operate
reliably down to 4.35V over temperature.
Table 1. Voltage Threshold Programming
V1
5.0
3.3
3.3
3.3
3.3
2.5
2.5
2.5
2.5
V2
3.3
2.5
1.8
1.5
1.2
1.8
1.5
1.2
1.0
S1
V1
S2
V1
Open
V1
GND
Open
V1
Open
Open
GND
GND
GND
V1
The same system using a supervisor with only 2.5%
accuracy needs to work reliably down to 4.25V (4.375V
125mV)or15%below5V,requiringthemonitoredsystem
to work over a much wider operating voltage range.
Open
GND
Open
V1
GND
Note: Open = open circuit or driven by a three state buffer in high
impedance state with leakage current less than 10μA.
29045fd
10
LTC2904/LTC2905
APPLICATIONS INFORMATION
In any supervisory application, supply noise riding on
the monitored DC voltage can cause spurious resets,
particularly when the monitored voltage is near the reset
threshold. A less desirable but common solution to this
problem is to introduce hysteresis around the nominal
threshold. Notice however, this hysteresis introduces an
error term in the threshold accuracy. Therefore, a 2.5%
accurate monitor with 1.0% hysteresis is equivalent to
a 3.5% monitor with no hysteresis.
Selecting the Reset Timing Capacitor
TheresettimeoutperiodforLTC2905isadjustableinorder
toaccommodateavarietyofmicroprocessorapplications.
Connecting a capacitor, C
, between the TMR pin and
TMR
ground sets the reset timeout period, t . The following
RST
formula determines the value of capacitor needed for a
particular reset timeout period:
–9
C
= t
• 110 • 10 [F/s]
TMR
RST
For example, using a standard capacitor value of 22nF
would give a 22000/110 = 200ms delay.
The LTC2904/LTC2905 takes a different approach to solve
this problem of supply noise causing spurious reset. The
first line of defense against this spurious reset is a first
order low pass filter at the output of the comparator. Thus,
the comparator output goes through a form of integration
before triggering the output logic. Therefore, any kind of
transient at the input of the comparator needs to be of
sufficient magnitude and duration before it can trigger a
change in the output logic.
Figure 1 shows the desired delay time as a function of the
value of the timer capacitor that should be used:
Leaving the TMR pin open with no external capacitor gen-
erates a reset timeout of approximately 200μs. For long
reset timeout, the only limitation is the availability of large
value capacitor with low leakage. The TMR capacitor will
never charge if the leakage current exceeds the minimum
TMR charging current of 2.1μA (typical).
The second line of defense is the programmed delay time
tRST (200ms for LTC2904 and using an external capacitor
for LTC2905). This delay will eliminate the effect of any
10000
1000
100
10
supply noise whose frequency is above 1/t
and RST output.
on the RST
RST
WheneitherV1orV2dropsbelowitsprogrammedthresh-
old, theRST pin asserts low (RST weakly pulls high). Then
when the supply recovers above the programmed thresh-
old, the reset-pulse-generator timer starts counting.
1
If the supply remains above the programmed threshold
when the timer finishes counting, the RST pin weakly
pulls high (RST asserts low). However, if the supply falls
below the programmed threshold any time during the
period when the timer is still counting, the timer resets
and it starts fresh when the supply next rises above the
programmed threshold.
0.1
10p
100p
1n
10n
(FARAD)
100n
1μ
C
TMR
29045 F01
Figure 1. Reset Timeout Period vs Capacitance
Note that this second line of defense is only effective
for a rising supply and does not affect the sensitivity of
the system to a falling supply. Therefore, the first line of
defense that works for both cases of rising and falling is
necessary. These two approaches prevent spurious reset
caused by supply noise without sacrificing the threshold
accuracy.
29045fd
11
LTC2904/LTC2905
APPLICATIONS INFORMATION
RST and RST Output Characteristics
Output Rise and Fall Time Estimation
The DC characteristics of the RST and RST pull-up and
pull-down strength are shown in the Typical Performance
Characteristics section. Both RST and RST have a weak
The RST and RST outputs have strong pull-down capabil-
ity. The following formula estimates the output fall time
(90% to 10%) for a particular external load capacitance
internal pull-up to V = Max (V1, V2) and a strong pull-
(C
):
CC
LOAD
down to ground.
t
≈ 2.2 • R • C
PD LOAD
FALL
Theweakpull-upandstrongpull-downarrangementallow
thesetwopinstohaveopen-drainbehaviorwhilepossess-
ing several other beneficial characteristics.
where R is the on-resistance of the internal pull-down
PD
transistor estimated to be typically 40Ω at room tempera-
ture (25°C) and C
is the external load capacitance on
LOAD
The weak pull-ups eliminate the need for external pull-up
resistorswhentherisetimeonthesepinsisnotcritical.On
the other hand, the open-drain RST configuration allows
for wired-OR connections and can be useful when more
than one signal needs to pull down on the RST line.
the pin. Assuming a 150pF load capacitance, the fall time
is about 13ns.
The rise time, on the RST and RST pins is limited by weak
internal pull-up current sources to V . The following
CC
formula estimates the output rise time (10% to 90%) at
As noted in the Power-Up and Power-Down sections the
the RST and RST pins:
circuitsthatdriveRSTandRSTarepoweredbyV .During
CC
t
≈ 2.2 R • C
PU LOAD
RISE
fault condition, V of at least 1V guarantees a maximum
CC
where R is the on-resistance of the pull-up transistor.
V
OL
= 0.4V at RST. However, at V = 1V the weak pull-up
PU
CC
Notice that this pull-up transistor is modeled as a
6μA current source in the Block Diagram as a typical
representation.
current on RST is barely turned on. Therefore, an external
pull-up resistor of no more than 100k is recommended on
the RST pin if the state and pull-up strength of the RST
pin is crucial at very low V .
CC
The on-resistance as a function of the V = Max (V1, V2)
CC
voltage (for V > 1V) at room temperature is estimated
Note however, by adding an external pull-up resistor, the
pull-up strength on the RST pin is increased. Therefore,
if it is connected in a wired-OR connection, the pull-down
strength of any single device needs to accommodate this
additional pull-up strength.
CC
as follows:
6•105
MAX(V1,V2)–1V
RPU
=
Ω
At V = 3.3V, R is about 260k. Using 150pF for load
CC
PU
capacitance, the rise time is 86μs. An external pull-up
resistor may be used if the output needs to pull up faster
and/or to a higher voltage, for example: the rise time re-
duces to 3.3μs for a 150pF load capacitance, when using
a 10k pull-up resistor.
29045fd
12
LTC2904/LTC2905
TYPICAL APPLICATIONS
2.5V, 1.2V Supply Monitor, 10% Tolerance
3.3V, 1.2V Dual Supply Monitor with LED Power Good Indicator,
7.5% Tolerance and Adjustable Timer
3.3V
510Ω
V2
V1
S2
V2
V1
RST
RST
TOL
1.2V
2.5V
1.2V
LTC2904
LTC2904
LED
RST
RST
GND
S2
0.1μF
0.1μF
0.1μF
0.1μF
SYSTEM
RESET
SYSTEM
RESET
S1
S1
TOL
GND
29045 TA02
29045 TA03
5V, 3.3V Dual Supply Monitor with Voltage
Margining for Automated On-Board Testing
5V
DC/DC
CONVERTER
SYSTEM
LOGIC
3.3V
V1
V2
TMR
GND
RST
LTC2905
V
IN
0.1μF
S1
SUPPLY
CONTROLLER
0.1μF
22nF
THREE-STATE
S2
TOL
29045 TA04
3.3V, 1.2V Dual Supply Monitor with Asymmetric Hysteresis, 5%
Tolerance (Supplies Rising), 10% Tolerance (After RST Goes Low)
V2
V1
RST
TOL
RST
1.2V
3.3V
LTC2904
10k
0.1μF
S2
0.1μF
S1
SYSTEM
RESET
GND
29045 TA05
29045fd
13
LTC2904/LTC2905
PACKAGE DESCRIPTION
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 0.05
(2 SIDES)
R = 0.115
0.40 0.10
3.00 0.10
(2 SIDES)
TYP
5
R = 0.05
TYP
8
0.70 0.05
2.55 0.05
1.15 0.05
2.00 0.10
PIN 1 BAR
TOP MARK
PIN 1
(2 SIDES)
R = 0.20 OR
(SEE NOTE 6)
0.25 × 45°
PACKAGE
OUTLINE
0.56 0.05
(2 SIDES)
CHAMFER
4
1
(DDB8) DFN 0905 REV B
0.25 0.05
0.50 BSC
0.25 0.05
0.75 0.05
0.200 REF
0.50 BSC
2.20 0.05
(2 SIDES)
2.15 0.05
(2 SIDES)
0 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
29045fd
14
LTC2904/LTC2905
PACKAGE DESCRIPTION
TS8 Package
8-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1637)
2.90 BSC
(NOTE 4)
0.52
MAX
0.65
REF
1.22 REF
1.50 – 1.75
(NOTE 4)
2.80 BSC
1.4 MIN
3.85 MAX 2.62 REF
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.22 – 0.36
8 PLCS (NOTE 3)
0.65 BSC
0.80 – 0.90
0.20 BSC
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.95 BSC
0.09 – 0.20
(NOTE 3)
TS8 TSOT-23 0802
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
29045fd
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC2904/LTC2905
TYPICAL APPLICATION
3.3V, 1.2V Dual Supply Monitor with LED Power Good Indicator,
7.5% Tolerance and Adjustable Timer
3.3V 1.8V
2.5V
V2
V1
V2
V1
1.2V
LTC2905
LTC2905
0.1μF
22nF
TMR
S2
0.1μF
TOL
0.1μF
510Ω
TMR
GND
RST
TOL
S2
0.1μF
22nF
S1
LED
S1
GND
RST
29045 TA06
RELATED PARTS
PART NUMBER
LTC690
DESCRIPTION
COMMENTS
5V Supply Monitor, Watchdog Timer and Battery Backup
3.3V Supply Monitor, Watchdog Timer and Battery Backup
5V Supply Monitor and Watchdog Timer
4.65V Threshold
2.9V Threshold
4.65V Threshold
LTC694-3.3
LTC699
LTC1232
5V Supply Monitor, Watchdog Timer and Pushbutton Reset
4.37V/4.62V Threshold
LTC1326/LTC1326-2.5
Micropower Precision Triple Supply Monitor
for 5V/2.5V, 3.3V and ADJ
4.725V, 3.118V, 1V Threshold ( 0.75%)
LTC1536
Precision Triple Supply Monitor for PCI Applications
Micropower Triple Supply Monitor for 2.5V/5V, 3.3V and ADJ
Micropower Triple Supply Monitor with Open-Drain Reset
Meets PCI t
Timing Specifications
FAIL
LTC1726-2.5/LTC1726-5
LTC1727-2.5/LTC1727-5
Adjustable RESET and Watchdog Timeouts
Individual Monitor Outputs in MSOP
5-Lead SOT-23 Package
LTC1728-1.8/LTC1728-3.3 Micropower Triple Supply Monitor with Open-Drain Reset
LTC1728-2.5/LTC1728-5
LTC1985-1.8
LTC2900
Micropower Triple Supply Monitor with Open-Drain Reset
Micropower Triple Supply Monitor with Push-Pull Reset Output
Programmable Quad Supply Monitor
5-Lead SOT-23 Package
5-Lead SOT-23 Package
Adjustable RESET, 10-Lead MSOP, DFN Packages
LTC2901
Programmable Quad Supply Monitor
Adjustable RESET and Watchdog Timer,
16-Lead SSOP Package
LTC2902
Programmable Quad Supply Monitor
Precision Quad Supply Monitor
Selectable Tolerance, RESET Disable for Margining
Functions, 16-Lead SSOP Package
LTC2903-1
LTC2906
Ultralow Voltage RESET, 6-Lead SOT-23 Package
Dual Supply Monitor with One Pin-Selectable Threshold and
One Adjustable Input
0.5V Adjustable Threshold and Three Supply
Tolerances, 8-Lead SOT-23 and DFN Packages
LTC2907
LTC2908
Dual Supply Monitor with One Pin-Selectable Threshold and
One Adjustable Input
0.5V Adjustable Threshold, Adjustable RESET Timer
and Three Supply Tolerances, 8-Lead SOT-23 and
DFN Packages
Precision Six Supply Monitors
Ultralow Voltage RESET, 8-Lead SOT-23 and DFN
Packages
29045fd
LT 1109 REV D • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
© LINEAR TECHNOLOGY CORPORATION 2003
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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