LTC1985-1.8 [Linear]
Micropower Precision Triple Supply Monitor with Push-Pull Reset Output in a 5-Lead SOT-23 Package; 微精密三通道电源监视器采用推拉式的5引脚SOT- 23封装复位输出
| 型号： | LTC1985-1.8 |
| 厂家： | 
Linear |
| 描述： | Micropower Precision Triple Supply Monitor with Push-Pull Reset Output in a 5-Lead SOT-23 Package |
| 文件： | 总8页 (文件大小：138K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Final Electrical Specifications
LTC1985-1.8
Micropower Precision
Triple Supply Monitor
with Push-Pull Reset Output
in a 5-Lead SOT-23 Package
March 2000
U
FEATURES
DESCRIPTIO
The LTC®1985-1.8 is a triple supply monitor intended for
systems with multiple supply voltages. The reset output
remains low until all three supplies have been in compli-
ance for 200ms. Tight 1.5% accuracy specifications and
glitch immunity ensure reliable reset operation without
false triggering.
■
Monitors Three Inputs Simultaneously:
3V, 1.8V and Adjustable
■
±1.5% Threshold Accuracy Over Temperature
■
Very Low Supply Current: 10µA Typ
■
200ms Reset Time Delay
■
Power Supply Glitch Immunity
■
Guaranteed RESET for VCC3 ≥ 1V or VCC18 ≥ 1V
The RST output is guaranteed to be in the correct state for
VCC18 or VCC3 down to 1V. The LTC1985 may also be
configured to monitor any one or two VCC inputs instead
of three, depending on system requirements.
■
3V Active-Low Push-Pull Reset Output
■
5-Lead SOT-23 Package
U
APPLICATIO S
Verylow(10µAtypical)supplycurrentmakestheLTC1985
ideal for power conscious systems.
■
Desktop Computers
■
The LTC1985 is available in a 5-lead SOT-23 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Notebook Computers
■
Intelligent Instruments
■
Portable Battery-Powered Equipment
■
Network Servers
U
TYPICAL APPLICATIO
3V
1.8V
2.5V
DC/DC
CONVERTER
SYSTEM
LOGIC
1
RST
5
4
3
V
V
V
CC3
LTC1985-1.8
CC18
R1
130k
1%
0.1µF
CCA
R2
100k
1%
GND
0.1µF
1985-1.8 TA01
2
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-
tation that the interconnection ofits circuits as described herein willnotinfringe on existing patentrights.
1
LTC1985-1.8
W W
U W
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ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Notes 1, 2)
VCC3, VCC18, VCCA ...................................... –0.3V to 7V
RST .......................................... –0.3V to (VCC3 + 0.3V)
Operating Temperature Range
(Note 3) ............................................. – 40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................ 300°C
ORDER
TOP VIEW
PART NUMBER
RST 1
GND 2
5 V
4 V
CC3
LTC1985ES5-1.8
V
CCA
3
CC18
S5 PACKAGE
5-LEAD PLASTIC SOT-23
S5 PART MARKING
LTNM
TJMAX = 125°C, θJA = 250°C/W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specificaitons are at TA = 25°C. VCC3 = 3V, VCC18 = 1.8V, VCCA = VCC3 unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
2.760
1.656
0.985
1
TYP
MAX
2.850
1.710
1.015
7
UNITS
V
V
V
V
Reset Threshold V
Reset Threshold V
Reset Threshold V
V
V
V
Input Threshold
●
●
●
●
2.805
1.683
1.000
V
V
V
V
RT3
RT18
RTA
CC3
CC3
Input Threshold
CC18
CCA
CC18
Input Threshold
CCA
V
V
, V Operating Voltage
CC3 CC18
RST in Correct Logic State
CCOP
VCC3
I
Supply Current
V
V
> V
CC3
●
●
1
10
2
20
µA
µA
CC3
CC18
CC18
< V , V
= 3V (Note 4)
CC3 CC3
I
I
t
t
V
V
Supply Current
V
V
< V , V = 1.8V (Note 4)
CC3 CC18
●
●
●
1
2
µA
nA
ms
µs
VCC18
VCCA
RST
CC18
CC18
Input Current
= 1V
CCA
–15
140
0
15
CCA
Reset Pulse Width
Undervoltage Detect to RST
RST Low
, V
200
110
280
V
V
or V
Less Than Reset
CCA
UV
CC
CC18 CC3
Threshold V by More Than 1%
RT
V
V
Output Voltage Low, RST
I
I
I
I
= 2.5mA, V
= 100µA, V
= 100µA, V
= 100µA, V
= 3V, V
= 1V, V
= 0V, V
= 1V, V
= 0V
= 0V
= 1V
= 1V
●
●
●
●
0.15
0.05
0.05
0.05
0.4
0.3
0.3
0.3
V
V
V
V
OL
SINK
SINK
SINK
SINK
CC3
CC3
CC3
CC3
CC18
CC18
CC18
CC18
Output Voltage High, RST
I
= 200µA
●
0.8V
V
OH
SOURCE
CC3
extended temperature limits of –40°C to 85°C but are not tested at these
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
temperatures.
Note 4: Both V
and V
can act as the supply depending on which pin
CC18
Note 2: All voltage values are with respect to GND.
CC3
has the greatest potential.
Note 3: The LTC1985E is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and assured to meet the
2
LTC1985-1.8
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VCCA Input Current
vs Input Voltage
IVCC3 vs Temperature
IVCC18 vs Temperature
15
14
13
12
11
10
9
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
2.0
1.5
V
V
V
= 3V
= 3V
T
= 25°C
CC3
CCA
CC18
A
= 1.8V
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
8
7
6
5
–60
20
TEMPERATURE (°C)
60 80
–40 –20
0
40
100
–60
20
TEMPERATURE (°C)
60 80
0.80 0.85 0.90 0.95
1
1.05 1.10 1.15 1.20
–40 –20
0
40
100
INPUT VOLTAGE (V)
1985-18 G01
1985-18 G02
1985-18 G03
VCC18 Threshold Voltage
vs Temperature
VCCA Threshold Voltage
vs Temperature
VCC3 Threshold Voltage
vs Temperature
2.845
2.835
2.825
2.815
2.805
2.795
2.785
2.775
2.765
1.710
1.700
1.690
1.680
1.670
1.660
1.650
1.015
1.010
1.005
1.000
0.995
0.990
0.985
–60
20
TEMPERATURE (°C)
60 80
–40 –20
0
40
100
40 60
TEMPERATURE (°C)
–60 –40 –20
0
20
80 100
40 60
TEMPERATURE (°C)
–60 –40 –20
0
20
80 100
1985-18 G05
1985-18 G06
1985-18 G04
Typical Transient Duration
vs Comparator Overdrive
Reset Pulse Width
vs Temperature
450
400
350
300
250
200
150
100
50
280
260
T
A
= 25°C
RESET OCCURS
ABOVE CURVE
240
220
200
180
160
0
0.1
140
1
10
100
–20
0
20 40
80 100
–60 –40
60
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V
)
CC
TEMPERATURE (°C)
1985-18 G07
1985-18 G08
3
LTC1985-1.8
U
U
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PI FU CTIO S
VCC18 (Pin 4): 1.8V Sense Input and Power Supply Pin.
This pin is used on the LTC1985 to provide power to the
partwhenthevoltageonVCC18 isgreaterthanthevoltage
on VCC3. Bypass to ground with a ≥0.1µF ceramic
capacitor.
RST (Pin 1): Reset Logic Output. Active low, 3V push-
pull output. Asserted when one or all of the supplies are
below trip thresholds and held for 200ms after all sup-
plies become valid.
GND (Pin 2): Ground.
V
CC3 (Pin 5): 3V Sense Input and Power Supply Pin. This
V
CCA (Pin 3): 1V Sense, High Impedance Input. If unused
pin provides power to the part when the voltage on VCC3
is greater than the voltage on VCC18. Bypass to ground
with a ≥0.1µF ceramic capacitor.
it can be tied to either VCC3 or VCC18
.
W
BLOCK DIAGRA
LTC1985-1.8
–
+
V
5
CC3
POWER
DETECT
V
INTERNAL
CC
V
CC3
V
4
CC18
–
+
200ms PULSE GENERATOR
1
RST
200ms
DELAY
–
+
V
3
2
CCA
GND
BANDGAP
REFERENCE
1985-18 BD
4
LTC1985-1.8
W U
W
TI I G DIAGRA
VCC Monitor Timing
V
RTX
V
CCX
t
RST
RST
1985-18 TD
W U U
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APPLICATIO S I FOR ATIO
Supply Monitoring
thresholds, aninternaltimerisstartedandRSTisreleased
after 200ms.
The LTC1985 is a low power, high accuracy triple supply
monitoring cirucit with a single 200ms microprocessor
reset output.
RST is reasserted whenever any one of the VCC inputs
drops below its predetermined threshold and remains
asserted until 200ms after all of the VCC inputs are above
their thresholds.
All three VCC inputs must be above predetermined thresh-
olds for reset not to be invoked. The LTC1985 will assert
reset during power-up, power-down and brownout condi-
tions on any one or all of the VCC inputs.
Power-Down
On power-down, once any of the VCC inputs drop below its
threshold, RST is held at a logic low. A logic low of 0.3V is
guaranteed until both VCC3 and VCC18 drop below 1V.
3V or 1.8V Power Detect
The LTC1985 is powered from the 3V input pin (VCC3) or
the 1.8V input pin (VCC18), whichever pin has the highest
potential. This ensures the part pulls the RST pin low as
soon as either input pin is ≥1V.
Override Functions
TheVCCA pin, ifunused, canbetiedtoeitherVCC3 orVCC18
.
This is an obvious solution since the trip points for VCC3
and VCC18 will always be greater than the trip point for
Power-Up
VCCA. Likewise, the VCC18, if unused, can be tied to VCC3
.
Upon power-up, either the VCC18 or VCC3 pin, can power
the part. This ensures that RST will be low when either
VCC18 or VCC3 reaches 1V. As long as any one of the VCC
inputs is below its predetermined threshold, RST will stay
a logic low. Once all of the VCC inputs rise above their
VCC3 must always be used. Tying VCC3 to VCC18 and
operating off of a 1.8V supply will result in the continuous
assertion of RST.
5
LTC1985-1.8
TYPICAL APPLICATIO S
U
Triple Supply Monitor (3V, 1.8V and Adjustable)
LTC1985-1.8
5
4
3
2
1
SYSTEM RESET
3V
V
V
V
RST
CC3
1.8V
CC18
CCA
ADJUSTABLE SUPPLY
OR DC/DC FEEDBACK
DIVIDER
R1*
R2*
GND
1985-18 TA02
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Dual Supply Monitor (3V and 1.8V, Defeat VCCA Input)
LTC1985-1.8
5
4
3
2
1
3V
V
V
V
RST
SYSTEM RESET
CC3
1.8V
CC18
CCA
GND
1985-18 TA03
Dual Supply Monitor (3V Plus Adjustable)
LTC1985-1.8
5
4
3
2
1
V
V
V
RST
3V
SYSTEM RESET
CC3
CC18
CCA
R1*
ADJUSTABLE
SUPPLY
R2*
GND
1985-18 TA04
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
6
LTC1985-1.8
U
TYPICAL APPLICATIO S
Using VCCA Tied to DC/DC Feedback Divider
2.5V
27.4k
1%
LTC1985-1.8
LTC1435
V
5
4
3
2
1
6
SYSTEM RESET
3V
V
RST
CC3
OSENSE
2.26k
1%
1.8V
V
V
CC18
CCA
22.6k
1%
GND
ADJUSTABLE
RESET TRIP
THRESHOLD 2.31V
1985-18 TA05
Resistor on RST Output to Ground Ensures RST Valid to VCC = 0V
Typical Application Showing Resistor on RST Output to Ground
RST Voltage vs VCC3 with a Resistor on RST to Ground
LTC1985-1.8
4
5
4
3
2
1
V
= V
= V
CC18 CCA
3V
V
V
V
RST
CC3
CC3
R3
100k
1.8V
CC18
CCA
R1
ADJUSTABLE
SUPPLY
3
2
1
0
R2
GND
1985-18 TA06
2
3
0
4
1
V
(V)
CC3
1985-18 TA06b
7
LTC1985-1.8
U
TYPICAL APPLICATIO
Triple Supply Monitor with Manual Reset Button
2.5V
= 2.3V
V
1.8V 3V
TRIP
1
RST
5
4
3
V
V
V
CC3
100nF
LTC1985-1.8
CC18
R1
130k
0.1%
R3*
10k
5%
100nF
CCA
GND
2
R2
100k
0.1%
MANUAL
1985-18 TA02
RESET BUTTON
(NORMALLY OPEN)
V
R2
CCA
V
TRIP
=
(R1 + R2)
V
V
TRIP
– 1
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
R1 = R2
(
)
CCA
U
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTIO
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
2.60 – 3.00
(0.102 – 0.118)
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
1.50 – 1.75
(0.059 – 0.069)
0.00 – 0.15
(0.00 – 0.006)
0.90 – 1.45
(0.035 – 0.057)
0.35 – 0.55
(0.014 – 0.022)
0.35 – 0.50
(0.014 – 0.020)
FIVE PLACES (NOTE 2)
0.90 – 1.30
(0.035 – 0.051)
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
0.95
(0.037)
REF
S5 SOT-23 0599
1.90
(0.074)
REF
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
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1985i LT/TP 0300 4K • PRINTED IN THE USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
8
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 2000
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