LTC2900-2IMS#PBF [Linear]
LTC2900 - Programmable Quad Supply Monitor with Adjustable Reset Timer; Package: MSOP; Pins: 10; Temperature Range: -40°C to 85°C;
| 型号： | LTC2900-2IMS#PBF |
| 厂家： | 
Linear |
| 描述： | LTC2900 - Programmable Quad Supply Monitor with Adjustable Reset Timer; Package: MSOP; Pins: 10; Temperature Range: -40°C to 85°C 光电二极管 |
| 文件： | 总16页 (文件大小：201K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC2900
Programmable Quad Supply
Monitor with Adjustable Reset Timer
U
FEATURES
DESCRIPTIO
■
Simultaneously Monitors Four Supplies
The LTC®2900 is a programmable supply monitor for
■
16 User Selectable Combinations of 5V, 3.3V, 3V,
2.5V, 1.8V, 1.5V and/or ±Adjustable Voltage
Thresholds
systemswithuptofoursupplyvoltages. Oneof16preset
or adjustable voltage monitor combinations can be se-
lected using an external resistor divider connected to the
program pin. The preset voltage thresholds are accurate
to ±1.5% over temperature.
■
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage Over Temperature
Low Supply Current: 43µA Typ
Adjustable Reset Time
Small MSOP and 3mm × 3mm DFN Packages
Manual Reset Pin
■
■
■
■
■
■
■
■
The reset delay time is adjustable using an external
capacitor and the manual reset input may be used with a
momentaryswitchtoissueresetpulseswithprogrammed
duration. Tight voltage threshold accuracy and glitch
immunity ensure reliable reset operation without false
triggering. The RST output is guaranteed to be in the
correctstateforVCC downto1V.TheLTC2900-1features
an open-drain RST output, while the LTC2900-2 has a
push-pull RST output.
Open-Drain RST Output (LTC2900-1)
Push-Pull RST Output (LTC2900-2)
Power Supply Glitch Immunity
Guaranteed RST for VCC ≥ 1V
U
APPLICATIO S
The 43µA supply current makes the LTC2900 ideal for
power conscious systems and it may be configured to
monitor less than four inputs. The parts are available in
the 10-lead MSOP and the 10-lead 3mm × 3mm DFN
packages.
■
Desktop and Notebook Computers
■
Multivoltage Systems
■
Telecom Equipment
■
Portable Battery-Powered Equipment
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
Network Servers
U
TYPICAL APPLICATIO
Quad Supply Monitor (5V, 3.3V, 2.5V, 1.8V)
5V
3.3V
2.5V
1.8V
DC/DC
CONVERTER
SYSTEM
LOGIC
V3
V1
LTC2900-2
V2
V4
C1
0.1µF
C2
0.1µF
V
REF
RST
PBR
CRT
R1
59k
1%
V
PG
GND
PUSH-BUTTON
RESET
R2
40.2k
1%
C
RT
47nF
2900 TA01
t
= 216ms
RST
2900f
1
LTC2900
W W
U W
(Notes 1, 2, 3)
ABSOLUTE AXI U RATI GS
V1, V2, V3, V4, VPG, PBR............................. –0.3V to 7V
RST (LTC2900-1)........................................ –0.3V to 7V
RST (LTC2900-2).......................... –0.3V to (V2 + 0.3V)
CRT ............................................. –0.3V to (VCC + 0.3V)
VREF ............................................. –0.3V to (VCC + 0.3V)
Reference Load Current (IVREF) ............................ ±1mA
V4 Input Current (–ADJ Mode) ............................ –1mA
Operating Temperature Range
LTC2900-1C/LTC2900-2C ....................... 0°C to 70°C
LTC2900-1I/LTC2900-2I .................... –40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
U W
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
NUMBER
TOP VIEW
LTC2900-1CMS
LTC2900-2CMS
LTC2900-1IMS
LTC2900-2IMS
LTC2900-1CDD
TOP VIEW
V3
V1
1
2
3
4
5
10 V2
V3
V1
CRT
RST
PBR
1
2
3
4
5
10 V2
LTC2900-2CDD
LTC2900-1IDD
LTC2900-2IDD
9
8
7
6
V4
9
8
7
6
V4
V
V
REF
PG
CRT
RST
PBR
V
REF
V
PG
GND
GND
MS PACKAGE
10-LEAD PLASTIC MSOP
MS PART MARKING
DD PART MARKING
DD PACKAGE
TJMAX = 125°C, θJA = 250°C/W
10-LEAD (3mm × 3mm) PLASTIC DFN
LTYJ
LTYL
LTYK
LTYM
LABU
LABW
LABV
LABX
TJMAX = 125°C, θJA = 43°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
4.600
3.036
2.760
2.300
1.656
1.380
0.492
–18
TYP
4.675
3.086
2.805
2.338
1.683
1.403
0.500
0
MAX
4.750
3.135
2.850
2.375
1.710
1.425
0.508
18
UNITS
V
V
V
V
V
V
V
V
V
5V, 5% Reset Threshold
3.3V, 5% Reset Threshold
3V, 5% Reset Threshold
2.5V, 5% Reset Threshold
1.8V, 5% Reset Threshold
1.5V, 5% Reset Threshold
ADJ Reset Threshold
V1 Input Threshold
●
●
●
●
●
●
●
●
●
V
V
RT50
RT33
RT30
RT25
RT18
RT15
RTA
V1, V2 Input Threshold
V2 Input Threshold
V
V2, V3 Input Threshold
V3, V4 Input Threshold
V3, V4 Input Threshold
V3, V4 Input Threshold
V4 Input Threshold
V
V
V
V
–ADJ Reset Threshold
Minimum Internal Operating Voltage
mV
V
RTAN
CC
RST in Correct Logic State,
1
V
V
V
V
V
Rising Prior to Program
CC
CC
CC
CC
PG
V
V
V
Minimum Required for Programming
Reference Voltage
Rising
●
●
●
●
●
2.42
V
V
CCMINP
REF
≥ 2.3V, I
= ±1mA, C
≤ 1000pF
REF
1.192
0
1.210
43
1.228
VREF
Programming Voltage Range
≥ V
V
REF
V
PG
CCMINP
I
I
V
Input Current
= V
REF
±20
nA
VPG
V1
PG
V1 Input Current
V1 = 5V, I
= 12µA, (Note 4)
75
µA
VREF
2900f
2
LTC2900
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, unless otherwise noted. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
0.8
MAX
UNITS
I
I
V2 Input Current
V3 Input Current
V2 = 3.3V
●
2
µA
V2
V3
V3 = 2.5V
V3 = 0.55V (ADJ Mode)
●
●
0.52
1.2
15
µA
nA
–15
I
V4 Input Current
V4 = 1.8V
V4 = 0.55V (ADJ Mode)
V4 = –0.05V (–ADJ Mode)
●
●
●
0.34
0.8
15
15
µA
nA
nA
V4
–15
–15
I
I
t
t
CRT Pull-Up Current
CRT Pull-Down Current
Reset Time-Out Period
V
V
C
= 0V
●
●
●
–1.4
10
–2
20
7
–2.6
30
µA
µA
ms
µs
CRT(UP)
CRT(DN)
RST
CRT
CRT
= 1.3V
= 1500pF
5
9
RT
V Undervoltage Detect to RST
X
V Less Than Reset Threshold V
by More Than 1%
150
UV
X
RTX
V
Output Voltage Low RST
I
= 2.5mA; V1 = 3V, V2 = 3V;
SINK
●
0.15
0.4
V
OL
OH
V3, V4 = 0V; V = 0V
PG
I
I
= 100µA; V2 = 1V; V1, V3, V4 = 0V
= 100µA; V1 = 1V; V2, V3, V4 = 0V
●
●
0.05
0.05
0.3
0.3
V
V
SINK
SINK
V
Output Voltage High RST (LTC2900-1)
(Note 5)
I
= 1µA
●
V2 – 1
V
SOURCE
Output Voltage High RST (LTC2900-2)
(Note 6)
I
= 200µA
●
0.8 • V2
V
SOURCE
Manual Reset Pin
V
V
PBR Input Threshold High
PBR Input Threshold Low
PBR Input Pulse Width
V
V
V
V
V
= 3.3V to 5.5V
= 3.3V to 5.5V
= 3.3V
●
●
●
●
1.6
1
V
V
IH
CC
0.4
IL
CC
t
t
I
150
ns
µs
µA
PBW
PBD
PBR
CC
Manual Reset Propagation Delay
PBR Pull-Up Current
= 3.3V, V
Falling
PBR
0.1
CC
= 0V
–10
PBR
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
the quiescent current, programming (transient) current and reference load
current.
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 LTC2900-1 has an internal pull-up to V2
of typically 6µA. However, an external pull-up resistor may be used when
faster rise times are required or for V voltages greater than V2.
OH
Note 3: The greater of V1, V2 is the internal supply voltage (V ).
CC
Note 6: The push-pull RST output pin on the LTC2900-2 is actively pulled up
to V2.
Note 4: Under static no-fault conditions, V1 will necessarily supply quiescent
current. If at any time V2 is larger than V1, V2 must be capable of supplying
TEST CIRCUITS
LTC2900-1
RST
LTC2900-1
LTC2900-2
RST
V1
V2
V3
V4
V1
V2
V3
V4
I
V1
V2
V3
V4
SINK
2.5mA,
I
I
SOURCE
1µA
SOURCE
200µA
100µA
RST
2900 F01
2900 F02
2900 F03
Figure 1. RST VOH Test
Figure 2. RST VOL Test
Figure 3. Active Pull-Up
RST VOH Test
2900f
3
LTC2900
W U
W
TI I G DIAGRA
Monitor Timing
V
RTX
V
X
t
t
t
RST
RST
PBD
t
UV
1.5V
RST
PBR
2900 TD
t
PBW
U W
TYPICAL PERFOR A CE CHARACTERISTICS
5V Threshold Voltage
vs Temperature
3.3V Threshold Voltage
vs Temperature
3V Threshold Voltage
vs Temperature
3.135
3.125
3.115
3.105
3.095
3.085
3.075
3.065
3.055
3.045
3.035
2.850
2.840
2.830
2.820
2.810
2.800
2.790
2.780
2.770
2.760
4.750
4.725
4.700
4.675
4.650
4.625
4.600
20
–60 –40 –20
TEMPERATURE (°C)
–60
80
–60
80
0
40 60 80 100
20
TEMPERATURE (°C)
60
20
TEMPERATURE (°C)
60
–40 –20
0
40
100
–40 –20
0
40
100
2900 G01
2900 G02
2900 G03
2.5V Threshold Voltage
vs Temperature
1.8V Threshold Voltage
vs Temperature
1.5V Threshold Voltage
vs Temperature
1.425
1.420
1.415
1.410
1.405
1.400
1.395
1.390
1.385
1.380
2.3750
2.3675
2.3600
2.3525
2.3450
2.3375
2.3300
2.3225
2.3150
2.3075
2.3000
1.710
1.705
1.700
1.695
1.690
1.685
1.680
1.675
1.670
1.665
1.660
1.655
–60
20
TEMPERATURE (°C)
60 80
–40 –20
0
40
100
40 60
–60 –40 –20
TEMPERATURE (°C)
–60
20
TEMPERATURE (°C)
60 80
0
20
80 100
–40 –20
0
40
100
2900 G06
2900 G04
2900 G05
2900f
4
LTC2900
U W
TYPICAL PERFOR A CE CHARACTERISTICS
ADJ Threshold Voltage
vs Temperature
–ADJ Threshold Voltage
vs Temperature
VREF vs Temperature
0.018
0.012
0.006
0
1.228
1.222
1.216
1.210
1.204
1.198
1.192
0.508
0.506
0.504
0.502
0.500
0.498
0.496
0.494
0.492
–0.006
–0.012
–0.018
–60
20
TEMPERATURE (°C)
60 80
–60
20
TEMPERATURE (°C)
60 80
–60
20
TEMPERATURE (°C)
60 80
–40 –20
0
40
100
–40 –20
0
40
100
–40 –20
0
40
100
2900 G07
2900 G08
2900 G21
IV1 vs Temperature
IV2 vs Temperature
IV3 vs Temperature
100
90
80
70
60
50
40
30
20
10
0
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
V1 = 5V
V1 = 5V
V1 = 5V
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
–60
20
TEMPERATURE (°C)
60 80
–40 –20
0
40
100
–60
20
TEMPERATURE (°C)
60 80
–60
20
TEMPERATURE (°C)
60 80
–40 –20
0
40
100
–40 –20
0
40
100
2900 G09
2900 G10
2900 G11
Typical Transient Duration
vs Comparator Overdrive (V1, V2)
Typical Transient Duration
vs Comparator Overdrive (V3, V4)
IV4 vs Temperature
450
400
350
300
250
200
150
100
50
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
220
200
180
160
140
120
100
80
T
= 25°C
T
= 25°C
V1 = 5V
A
A
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
RESET OCCURS
ABOVE CURVE
RESET OCCURS
ABOVE CURVE
60
40
20
0
0
0.1
1
10
100
–60
20
TEMPERATURE (°C)
60 80
–40 –20
0
40
100
0.1
1
10
100
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V
)
RTX
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V
)
RTX
2900 G13
2900 G20
2900 G12
2900f
5
LTC2900
TYPICAL PERFOR A CE CHARACTERISTICS
U W
RST Output Voltage
vs V1, VPG = 0V
Reset Time-Out Period
vs Temperature
Reset Time-Out Period
vs Capacitance
8.9
8.4
7.9
7.4
6.9
6.4
5.9
5.4
4.9
10
1
5
4
3
2
1
0
T
= 25°C
C
= 1500pF
A
RT
V1 = V2 = V3 = V4
10k PULL-UP FROM RST TO V1
(SILVER MICA)
T
= 25°C
A
100m
10m
1m
100µ
100n
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
V1 (V)
–60
80
10p
100p
1n
10n
1µ
–40 –20
0
20 40 60
100
TEMPERATURE (°C)
C
(FARAD)
RT
2900 G14
2900 G15
2900 G16
RST High Level Output Voltage
vs Output Source Current
(LTC2900-2)
RST Voltage Output Low
vs Output Sink Current
RST, ISINK vs Supply Voltage
13
12
11
10
9
8
7
6
5
4
3
2
1
3.0
2.5
2.0
1.5
1.0
0.5
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
T
= 25°C
V1 = 5V
V2 = 3V
V3 = 2.5V
V4 = 1V
V2 = 3V
V1 = 5V
A
25°C
–40°C
85°C
V
= 0.4V
OL
–40°C
25°C
V
= 0.2V
OL
85°C
0
0
0.5
1
1.5
(mA)
2
2.5
0
1
3
4
5
6
2
0
10 20 30
50
70 80 90
40
60
V1 OR V2 (V)
I
SOURCE
I
(mA)
SINK
2900 G19
2900 G17
2900 G18
RST Pull-Up Current vs V2
(LTC2900-1)
RST Pull-Up Current vs V2
(LTC2900-2)
6
5
4
3
2
1
0
20
18
16
14
12
10
8
T
A
= 25°C
T
= 25°C
A
V
RT33
V
RT33
6
V
RT30
V
RT30
V
RT25
4
V
RT25
2
0
2
2.5
3.5
4
4.5
5
3
2
2.5
3.5
4
4.5
5
3
V2 (V)
V2 (V)
2900 G22
2900 G23
2900f
6
LTC2900
U
U
U
PI FU CTIO S
V3 (Pin 1): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V
operation. When using a switch, the switch is debounced
through the reset circuitry using the delay provided by the
CRT timing capacitor.
or ADJ. See Table 1 for details.
V1 (Pin 2): Voltage Input 1. Select from 5V or 3.3V. See
Table 1 for details. The greater of (V1, V2) is also VCC for
the device. Bypass this pin to ground with a 0.1µF (or
greater) capacitor.
GND (Pin 6): Ground.
VPG (Pin 7): Voltage Threshold Combination Select Input.
Connect to an external 1% resistive divider between VREF
and GND to select 1 of 16 combinations of preset and/or
±adjustable voltage thresholds (see Table 1). Do not add
capacitance on the VPG pin.
CRT (Pin 3): Reset Delay Time Programming Pin. Attach
anexternalcapacitor(CRT)toGNDtosetaresetdelaytime
of 4.6ms/nF. Leaving the pin open generates a minimum
delay of approximately 50µs. A 47nF capacitor will gener-
ate a 216ms reset delay time.
VREF (Pin 8): Buffered Reference Voltage. A 1.210V
nominal reference used for the programming voltage
(VPG) and for the offset of negative adjustable applica-
tions. The buffered reference can source and sink up to
1mA. The reference can drive a bypass capacitor of up to
1000pF without oscillation.
RST (Pin 4): Reset Logic Output. Active low with weak
pull-up to V2 (LTC2900-1) or active pull-up to V2
(LTC2900-2). Pulls low when any voltage input is below
theresetthresholdandheldlowfortheprogrammeddelay
time after all voltage inputs are above threshold. May be
pulled above V2 using an external pull-up (LTC2900-1
only).
V4 (Pin 9):Voltage Input 4. Select from 1.8V, 1.5V, ADJ or
–ADJ. See Table 1 for details.
V2 (Pin 10): Voltage Input 2. Select from 3.3V, 3V or 2.5V.
See Table 1 for details. The greater of (V1, V2) is also VCC
for the device. Bypass this pin to ground with a 0.1µF (or
greater) capacitor. RST is weakly pulled up to V2
(LTC2900-1). RST is actively pulled up to V2 in the
LTC2900-2.
PBR (Pin 5): Manual Reset Pin. Attach a push-button
switchbetweenthispinandground. Alogiclowonthispin
will pull RST low. When the PBR pin returns high, RST will
return high after the programmed reset delay assuming all
four voltage inputs are above threshold. A weak internal
pull-up allows the pin to be left floating for normal monitor
2900f
7
LTC2900
W
BLOCK DIAGRA
V1
–
+
POWER
DETECT
V
CC
V2
–
+
V1
2
V2
10
RESISTIVE
DIVIDER
MATRIX
V3
1
LTC2900-1
V2
–
+
V4
9
6µA
GND
6
RST
4
–
+
ADJUSTABLE
RESET PULSE
GENERATOR
V
CC
V
PG
2µA
A/D
7
LTC2900-2
V2
BUFFER
22µA
10µA
V
REF
1.210V
BANDGAP
REFERENCE
RST
4
8
V
CC
PBR
CRT
3
5
C
RT
2900 DB-1
2900f
8
LTC2900
W U U
APPLICATIO S I FOR ATIO
Power-Up
U
Table 1. Voltage Threshold Programming
V
PG
The greater of V1, V2 is the internal supply voltage (VCC).
On power-up, VCC will power the drive circuits for the RST
pin. This ensures that the RST output will be low as soon
asV1orV2reaches1V.TheRSToutputwillremainlowuntil
the part is programmed. After programming, if any one of
the VX inputs is below its programmed threshold, RST will
bealogiclow.OncealltheVXinputsriseabovetheirthresh-
olds, an internal timer is started and RST is released after
theprogrammeddelaytime.IfVCC<(V3–1)andVCC<2.4V,
the V3 input impedance will be low (1kΩ typ).
MODE V1 (V) V2 (V) V3 (V) V4 (V) R1 (kΩ) R2 (kΩ)
V
REF
0
1
5.0
5.0
3.3
3.3
3.3
5.0
5.0
5.0
5.0
5.0
3.3
3.3
3.3
5.0
5.0
5.0
3.3
3.3
2.5
2.5
2.5
3.3
3.3
3.3
3.0
3.0
2.5
2.5
2.5
3.3
3.3
3.0
ADJ
ADJ
ADJ
ADJ
1.5
2.5
2.5
2.5
2.5
ADJ
1.8
1.8
1.8
1.8
1.8
1.8
ADJ
–ADJ
ADJ
–ADJ
ADJ
ADJ
1.8
Open
93.1
86.6
78.7
71.5
66.5
59.0
53.6
47.5
40.2
34.8
28.0
22.1
16.2
9.53
Short
Short
9.53
16.2
22.1
28.0
34.8
40.2
47.5
53.6
59.0
66.5
71.5
78.7
86.6
93.1
Open
0.000
0.094
0.156
0.219
0.281
0.344
0.406
0.469
0.531
0.594
0.656
0.719
0.781
0.844
0.906
1.000
2
3
4
5
6
7
1.5
8
ADJ
ADJ
1.5
9
Monitor Programming
10
11
12
13
14
15
The LTC2900 input voltage combination is selected by
placing the recommended resistive divider from VREF to
GND and connecting the tap point to VPG, as shown in
Figure 4. Table 1 offers recommended 1% resistor values
ADJ
–ADJ
–ADJ
ADJ
ADJ
R1
1%
LTC2900
8
7
6
V
REF
V
PG
GND
R2
1%
Supply Monitoring
2900 F04
The LTC2900 is a low power, high accuracy program-
mable quad supply monitoring circuit with a common
reset output and a manual reset input. Reset timing is
adjustable using an external capacitor. Single pin pro-
gramming selects 1 of 16 input voltage monitor combina-
tions.Allfourvoltageinputsmustbeabovepredetermined
thresholds for the reset not to be invoked. The LTC2900
will assert the reset output during power-up, power-down
and brownout conditions on any one of the voltage inputs.
Figure 4. Monitor Programming
forthevariousmodes. ThelastcolumninTable1specifies
optimum VPG/VREF ratios (±0.01) to be used when pro-
gramming with a ratiometric DAC.
During power-up, once V1 or V2 reaches 2.4V max, the
monitor enters a programming period of approximately
150µs during which the voltage on the VPG pin is sampled
and the monitor is configured to the desired input combi-
nation.DonotaddcapacitancetotheVPG pin.Immediately
after programming, the comparators are enabled and
supply monitoring will begin.
The inverting inputs on the V3 and/or V4 comparators are
set to 0.5V when the positive adjustable modes are se-
lected (Figure 5). The tap point on an external resistive
divider, connected between the positive voltage being
2900f
9
LTC2900
APPLICATIO S I FOR ATIO
W U U
U
V
TRIP
8
9
LTC2900
V
REF
LTC2900
R4
R3
1%
1%
V4
–
V3 OR V4
+
R3
1%
R4
1%
+
–
V
TRIP
+
0.5V
–
2900 F06
Figure 6. Setting the Negative Adjustable Trip Point
2900 F05
Figure 5. Setting the Positive Adjustable Trip Point
Table 2. Suggested 1% Resistor Values for the ADJ Inputs
V
(V)
V
(V)
TRIP
R3 (kΩ)
2150
1780
1400
1300
1020
845
R4 (kΩ)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
SUPPLY
sensed and ground, is connected to the high impedance
noninverting inputs (V3, V4). The trip voltage is calculated
from:
12
11.25
9.4
10
8
7.5
7.5
6
7
R3
R4
VTRIP = 0.5V 1+
5.6
5
4.725
3.055
2.82
2.325
1.685
1.410
1.120
0.933
0.840
Inthenegativeadjustablemode, thenoninvertinginputon
the V4 comparator is connected to ground (Figure 6). The
tap point on an external resistive divider, connected be-
tween the negative voltage being sensed and the VREF pin,
is connected to the high impedance inverting input (V4).
VREF provides the necessary level shift required to operate
at ground. The trip voltage is calculated from:
3.3
3
511
464
2.5
1.8
1.5
1.2
1
365
237
182
124
86.6
68.1
R3
R4
0.9
VTRIP = –VREF
; VREF = 1.210V Nominal
Table 3. Suggested 1% Resistor Values for the –ADJ Input
In a negative adjustable application, the minimum value
forR4islimitedbythesourcingcapabilityofVREF (±1mA).
With no other load on VREF, R4 (minimum) is:
V
(V)
V
(V)
TRIP
R3 (kΩ)
187
R4 (kΩ)
121
SUPPLY
–2
–1.87
–4.64
–4.87
–9.31
–5
–5.2
–10
–12
464
121
1.21V ÷ 1mA = 1.21kΩ.
487
121
931
121
Tables 2 and 3 offer suggested 1% resistor values for
various adjustable applications.
–11.30
1130
121
2900f
10
LTC2900
W U U
APPLICATIO S I FOR ATIO
Although all four supply monitor comparators have built-
in glitch immunity, bypass capacitors on V1 and V2 are
recommended because the greater of V1 or V2 is also the
VCC for the device. Filter capacitors on the V3 and V4
inputs are allowed.
U
6 •105
V2 – 1
RPU
=
Ω
with V2 = 3.3V, RPU is about 260k. Using 150pF for load
capacitance, the rise time is 86µs. If the output needs to
pull up faster and/or to a higher voltage, a smaller
external pull-up resistor may be used. Using a 10k pull-
up resistor, the rise time is reduced to 3.3µs for a 150pF
load capacitance.
Power-Down
On power-down, once any of the VX inputs drop below
their threshold, RST is held at a logic low. A logic low of
0.4V is guaranteed until both V1 and V2 drop below 1V. If
the bandgap reference becomes invalid (VCC < 2V typ), the
part will reprogram once VCC rises above 2.4V max.
The LTC2900-2 has an active pull-up to V2 on the RST
output. The typical performance curve (RST Pull-Up Cur-
rent vs V2 curve) demonstrates that the pull-up current is
somewhat linear versus the V2 voltage and RPU is esti-
mated to be approximately 625Ω. A 150pF load capaci-
tance makes the rise time about 206ns.
Monitor Output Rise and Fall Time Estimation
The RST output has strong pull-down capability. If the
external load capacitance (CLOAD) is known, output fall
time (10% to 90%) is estimated using:
Selecting the Reset Timing Capacitor
The reset time-out period is adjustable in order to accom-
modate a variety of microprocessor applications. The
reset time-out period, tRST, is adjusted by connecting a
capacitor,CRT,betweentheCRTpinandground.Thevalue
of this capacitor is determined by:
t
FALL ≈ 2.2 • RPD • CLOAD
where RPD is the on-resistance of the internal pull-down
transistor. The typical performance curve (VOL vs ISINK
)
demonstrates that the pull-down current is somewhat
linear versus output voltage. Using the 25°C curve, RPD is
estimated to be approximately 40Ω. Assuming a 150pF
load capacitance, the fall time is about 13.2ns.
CRT = tRST • 217 • 10–9
with CRT in Farads and tRST in seconds. The CRT value per
millisecond of delay can also be expressed as CRT/ms =
217 (pF/ms).
Although the RST output of the LTC2900-1 is considered
to be “open-drain,” it does have weak pull-up capability
(see RST Pull-Up Current vs V2 curve). Output rise time
(10% to 90%) is estimated using:
Leaving the CRT pin unconnected will generate a mini-
mum reset time-out of approximately 50µs. Maximum
reset time-out is limited by the largest available low
leakage capacitor. The accuracy of the time-out period will
be affected by capacitor leakage (the nominal charging
current is 2µA) and capacitor tolerance. A low leakage
ceramic capacitor is recommended.
tRISE ≈ 2.2 • RPU • CLOAD
where RPU is the on-resistance of the pull-up transistor.
The on-resistance as a function of the V2 voltage at room
temperature is estimated using:
2900f
11
LTC2900
W U U
U
APPLICATIO S I FOR ATIO
Ensuring Reset Valid for VCC Down to 0V (LTC2900-2)
Some applications require the reset output (RST) to be
valid with VCC down to 0V. The LTC2900-2 is designed to
handle this requirement with the addition of an external
resistor from RST to ground. The resistor will provide a
path for stray charge and/or leakage currents, preventing
the RST output from floating to undetermined voltages
when connected to high impedance (such as CMOS logic
inputs). The resistor value should be small enough to
provide effective pull-down without excessively loading
the active pull-up circuitry. Too large a value may not pull
down well enough. A 100k resistor from RST to ground is
satisfactory for most applications.
U
TYPICAL APPLICATIO S
Quad Supply Monitor with Push-Button Reset
5V, 3V, 1.8V, 12V (ADJ)
1
2
3
4
5
10
9
1.8V
5V
3V
V3
V1
V2
V4
R3
2.15M
1%
LTC2900
8
CRT
RST
PBR
V
REF
7
SYSTEM
RESET
V
12V
PG
6
V
= 11.25V
TRIP
GND
C
RT
R4
100k
1%
NORMALLY
OPEN
2900 TA02
5V, –5V Monitor and Unused V2, V3 Inputs
Pulled Above Trip Thresholds
R3
464k
1%
1
2
3
4
5
10
9
V3
V1
V2
V4
5V
–5V
LTC2900
8
V
TRIP
= –4.64V
CRT
RST
PBR
V
REF
R1
16.2k
1%
7
R4
121k
1%
SYSTEM
RESET
V
PG
6
GND
C
RT
R2
86.6k
1%
2900 TA03
2900f
12
LTC2900
U
TYPICAL APPLICATIO S
5V, 3.3V, 12V, –5.2V Monitor with Manual Reset and LED Indication on RST
12V
R5
2.15M
1%
V
TRIP
= 11.25V
R3
487k
1%
1
2
3
4
5
10
9
3.3V
V3
V1
V2
V4
R6
100k
1%
5V
–5.2V
LTC2900-1
C
8
R4
RT
V
TRIP
= –4.87V
R
L1
CRT
RST
PBR
V
REF
121k
1k
7
1%
V
PG
LED
10k*
R1
93.1k
1%
6
SYSTEM
RESET
GND
MANUAL RESET
BUTTON
(NORMALLY OPEN)
R2
9.53k
1%
2900 TA05
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
Low Voltage Quad Supply Monitor 3.3V, 2.5V, 1V (ADJ), 0.9V (ADJ)
R5
86.6k
R3
68.1k
1%
1%
1
2
3
4
5
10
9
1V
V3
V1
V2
V4
2.5V
V
= 0.933V
TRIP
3.3V
0.9V
LTC2900
8
V
TRIP
= 0.84V
CRT
RST
PBR
V
REF
R1
86.6k
1%
7
SYSTEM
RESET
V
PG
6
R4
R6
100k
1%
GND
100k
1%
C
RT
R2
16.2k
1%
2900 TA04
2900f
13
LTC2900
U
PACKAGE DESCRIPTIO
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
0.675 ±0.05
3.50 ±0.05
2.15 ±0.05 (2 SIDES)
1.65 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
R = 0.115
TYP
6
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.38 ± 0.10
10
3.00 ±0.10
(4 SIDES)
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 5)
(DD10) DFN 0403
5
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.200 REF
2.38 ±0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. ALL DIMENSIONS ARE IN MILLIMETERS
3. 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
4. EXPOSED PAD SHALL BE SOLDER PLATED
5. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
2900f
14
LTC2900
U
PACKAGE DESCRIPTIO
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.2 – 3.45
(.126 – .136)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.497 ± 0.076
(.0196 ± .003)
REF
0.50
0.305 ± 0.038
(.0120 ± .0015)
TYP
(.0197)
10 9
8
7 6
BSC
RECOMMENDED SOLDER PAD LAYOUT
3.00 ± 0.102
(.118 ± .004)
NOTE 4
4.90 ± 0.15
(1.93 ± .006)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
GAUGE PLANE
1
2
3
4 5
0.53 ± 0.01
(.021 ± .006)
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.13 ± 0.076
(.005 ± .003)
MSOP (MS) 0802
0.50
(.0197)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
2900f
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
LTC2900
U
TYPICAL APPLICATIO
Monitor Eight Supplies Using Supervisory Cascade
12V (ADJ), 5V, 3.3V, 3V, 2.5V, 1.8V, 1V (ADJ), –5V (–ADJ)
MASTER
RESET
R5A
86.6k 1%
1V
R3B
464k 1%
–5V
R3A
2150k 1%
12V
3V
5V
2.5V
R4B
121k
1%
1
2
3
4
5
1
2
3
4
5
10
9
10
9
1.8V
3.3V
V3
V1
V2
V4
V3
V1
V2
V4
LTC2900-2
LTC2900-2
8
8
CRT
RST
PBR
V
CRT
RST
PBR
V
REF
REF
R4A
100k
1%
R6A
100k
1%
R1A
40.2k
1%
R1B
22.1k
1%
7
7
V
V
PG
PG
6
6
GND
GND
C
C
RTB
RTA
R2A
59k
1%
R2B
78.7k
1%
100k
20k
2900 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 Push-Button Reset
4.37V/4.62V Threshold
4.725V, 3.118V, 1V Thresholds (±0.75%)
Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (±0.75%)
LTC1326
Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ
LTC1326-2.5
LTC1536
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
Programmable Quad Supply Monitor
5-Lead SOT-23 Package
5-Lead SOT-23 Package
LTC2901
Adjustable Reset and Watchdog Timers, 16-Lead
Narrow SSOP Package
LTC2902
Programmable Quad Supply Monitor
Adjustable Reset Timer, Supply Tolerance and
Margining Functions, 16-Lead Narrow SSOP Package
2900f
LT/TP 0403 2K • PRINTED IN USA
16 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2002
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