LTC1536
Precision Triple Supply Monitor
for PCI Applications
FEATURES
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Simultaneously Monitors 5V, 3.3V and
Adjustable Inputs
Guaranteed Threshold Accuracy:
±0.75%
Low Supply Current: 100µA
Internal Reset Time Delay: 200ms
Manual Pushbutton Reset Input
Active Low and Active High Reset Outputs
Active Low “Soft” Reset Output
Power Supply Glitch Immunity
Guaranteed Reset for Either V
CC3
≥
1V or V
CC5
≥
1V
Meets PCI t
FAIL
Timing Specifications Rev 2.1
8-Pin SO and MSOP Packages
The LTC
®
1536 is designed for PCI local bus applications
with multiple supply voltages that require low power,
small size, high speed and high accuracy supply
monitoring.
For 3.3V and 5V supplies that are > 500mV below spec or
for the condition when the 5V supply falls below the 3.3V
supply, the LTC1536 has a very fast response time capable
of meeting the PCI t
FAIL
timing specification. Tight 0.75%
threshold accuracy and glitch immunity ensure reliable
reset operation without false triggering.
The RST output is guaranteed to be in the correct state for
V
CC5
or V
CC3
down to 1V. The 100µA typical supply current
makes the LTC1536 ideal for power-conscious systems.
A manual pushbutton reset input provides the ability to
generate a very narrow “soft” reset pulse (100µs typ) or a
200ms reset pulse equivalent to a power-on reset. Both
SRST and RST outputs are open-drain and can be OR-tied
with other reset sources.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
s
PCI-Based Systems
Desktop Computers
Notebook Computers
Intelligent Instruments
Portable Battery-Powered Equipment
Network Servers
TYPICAL APPLICATIO
Motherboard PCI RST Generation
3.3V
±
0.3V
0.1µF
1
5V
±
5%
0.1µF
2
3
4
PWR GOOD
R
PU
SELECTED TO MEET RISE TIME
SLEW RATE REQUIREMENTS (1k MIN)
1536 TA01
LTC1536
V
CC3
V
CC5
V
CCA
GND
PBR
SRST
RST
RST
8
7
6
5
PUSHBUTTON
RESET
R
PU
VOLTAGE (1V/DIV)
RST
PCI
LOCAL
BUS
U
Power Fail Waveform
5V Dropping Below 3.3V by 300mV
V
CC5
= 5V TO 3V STEP
V
CC3
= V
CCA
= 3.3V
4.7k PULL-UP FROM
RST TO V
CC3
V
CC5
5
4
3
2
RST
1
0
TIME (20ns/DIV)
1536 TA02
U
U
1
LTC1536
ABSOLUTE
(Notes 1, 2)
AXI U
RATI GS
Operating Temperature Range
LTC1536C .............................................. 0°C to 70°C
LTC1536I ............................................ – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
Terminal Voltage
V
CC3
, V
CC5
, V
CCA
.................................... – 0.3V to 7V
RST, SRST ............................................ – 0.3V to 7V
RST ......................................... – 0.3V to V
CC3
+ 0.3V
PBR .......................................................... – 7V to 7V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
CC3
V
CC5
V
CCA
GND
1
2
3
4
8
7
6
5
PBR
SRST
RST
RST
ORDER
PART NUMBER
LTC1536CMS8
MS8 PART MARKING
LTBV
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
V
CC3
= 3.3V, V
CC5
= 5V, V
CCA
= V
CC3
, T
A
= 25°C unless otherwise noted.
SYMBOL
V
RT3
V
RT5
V
RTA
V
CC
I
VCC3
I
VCC5
I
VCCA
t
RST
PARAMETER
Reset Threshold V
CC3
Reset Threshold V
CC5
Reset Threshold V
CCA
V
CC3
or V
CC5
Operating Voltage
V
CC3
Supply Current
V
CC5
Input Current
V
CCA
Input Current
Reset Pulse Width
CONDITIONS
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
0°C
≤
T
A
≤
70°C
– 40°C
≤
T
A
≤
85°C
RST in Correct Logic State
PBR = V
CC3
V
CC5
= 5V
V
CCA
= 1V, 0°C
≤
T
A
≤
70°C
V
CCA
= 1V, – 40°C
≤
T
A
≤
85°C
RST Low with 10kΩ Pull-Up to V
CC3
0°C to 70°C
– 40°C to 85°C
SRST Low with 10kΩ Pull-Up to V
CC3
V
CC5
, V
CC3
or V
CCA
Less Than Reset
Threshold V
RT
by 1%
q
q
q
q
q
q
q
q
q
q
q
q
q
q
t
SRST
t
UV
Soft Reset Pulse Width
V
CC
Undervoltage Detect to RST
2
U
U
W
W W
U
W
TOP VIEW
V
CC3
1
V
CC5
2
V
CCA
3
GND 4
8 PBR
7 SRST
6 RST
5 RST
ORDER
PART NUMBER
LTC1536CS8
LTC1536IS8
S8 PART MARKING
1536
1536I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 150°C/ W
MIN
2.962
2.925
4.687
4.625
0.992
0.980
1
TYP
2.985
2.985
4.725
4.725
1.000
1.000
100
10
MAX
3.000
3.008
4.750
4.762
1.007
1.007
7
200
20
5
15
280
300
200
UNITS
V
V
V
V
V
V
V
µA
µA
nA
nA
ms
ms
µs
µs
–5
– 15
140
140
50
0
0
200
200
100
13
LTC1536
ELECTRICAL CHARACTERISTICS
V
CC3
= 3.3V, V
CC5
= 5V, V
CCA
= V
CC3
, T
A
= 25°C unless otherwise noted.
SYMBOL
I
PBR
V
IL
V
IH
t
PW
t
DB
t
PB
V
OL
PARAMETER
PBR Pull-Up Current
PBR, RST Input Low Voltage
PBR, RST Input High Voltage
PBR Min Pulse Width
PBR Debounce
PBR Assertion Time for Transition
from Soft to Hard Reset Mode
RST Output Voltage Low
Deassertion of PBR Input to SRST
Output (PBR Pulse Width = 1µs)
PBR Held Less Than V
IL
, 0°C to 70°C
PBR Held Less Than V
IL
, – 40°C to 85°C
I
SINK
= 5mA
I
SINK
= 100µA
0°C
≤
T
A
≤
70°C
I
SINK
= 100µA
– 40°C
≤
T
A
≤
85°C
SRST Output Voltage Low
RST Output Voltage Low
V
OH
RST Output Voltage High (Note 3)
SRST Output Voltage High (Note 3)
RST Output Voltage High
t
PHL
t
PLH
t
FAIL
t
PF
Propagation Delay RST to RST
High Input to Low Output
Propagation Delay RST to RST
Low Input to High Output
V
CC5
or V
CC3
0.5V Undervoltage
to RST (Note 4)
V
CC5
< (V
CC3
– 300mV) RST (Note 4)
I
SINK
= 2.5mA
I
SINK
= 2.5mA
I
SOURCE
= 1µA
I
SOURCE
= 1µA
I
SOURCE
= 600µA
C
RST
= 20pF
C
RST
= 20pF
V
CC5
Drops Below 4.25V or V
CC3
Drops
Below 2.5V (Note 5)
V
CC5
Drops Below V
CC3
By 300mV
(Note 6)
q
q
CONDITIONS
PBR = 0V, 0°C
≤
T
A
≤
70°C
PBR = 0V, – 40°C
≤
T
A
≤
85°C
q
q
q
q
q
q
q
q
q
MIN
3
3
2
40
TYP
7
7
MAX
10
15
0.8
UNITS
µA
µA
V
V
ns
20
1.4
1.4
2.0
2.0
0.15
0.05
0.05
0.05
0.05
0.05
0.05
0.15
0.15
V
CC3
– 1
V
CC3
– 1
V
CC3
– 1
25
45
150
50
35
2.8
3.0
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
ms
s
s
V
V
V
V
V
V
V
V
V
V
V
V
ns
ns
V
CC3
= 1V, V
CC5
= 0V
V
CC3
= 0V, V
CC5
= 1V
V
CC3
= 1V, V
CC5
= 1V
V
CC3
= 1.1V, V
CC5
= 0V
V
CC3
= 0V, V
CC5
= 1.1V
V
CC3
= 1.1V, V
CC5
= 1.1V
q
q
q
q
q
q
q
q
q
q
q
450
90
ns
ns
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
All voltage values are with respect to GND.
Note 3:
The output pins SRST and RST have weak internal pull-ups to
V
CC3
of 6µA. However, external pull-up resistors may be used when faster
rise times are required.
Note 4:
Conforms to PCI Local Bus Specification Rev 2.1,
Sect. 4.3.2 for t
FAIL
.
Note 5:
V
CC3
or V
CC5
falling at – 0.1V/µs, time measured from
V
RTX
– 500mV to RST at 1.5V.
Note 6:
V
CC5
falling from 5V to 3V in
≤10ns,
time measured from
V
CC5
= (V
CC3
– 300mV) to RST at 1.5V.
3
LTC1536
TYPICAL PERFORMANCE CHARACTERISTICS
I
VCC3
vs Temperature
140
120
100
I
VCC3
(µA)
INPUT CURRENT (nA)
80
60
40
20
0
– 45
I
VCC5
(µA)
– 25
35
15
–5
55
TEMPERATURE (°C)
V
CC5
Threshold Voltage
vs Temperature
4.750
V
CC5
THRESHOLD VOLTAGE, V
RT5
(V)
V
CCA
THRESHOLD VOLTAGE, V
RTA
(V)
V
CC3
THRESHOLD VOLTAGE, V
RT3
(V)
4.745
4.740
4.735
4.730
4.725
4.720
4.715
4.710
4.705
4.700
– 60 – 40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
Reset Pulse Width
vs Temperature
225
RESET PULSE WIDTH, t
RST
(ms)
220
215
210
205
200
195
190
– 50
SOFT RESET PULSE WIDTH, t
SRST
(µs)
112.5
110.0
107.5
105.0
102.5
100.0
97.5
PBR ASSERTION TIME TO RESET, t
PB
(SEC)
– 25
50
25
0
TEMPERATURE (°C)
4
U W
75
1536 G01
1536 G04
I
VCC5
vs Temperature
20.0
17.5
15.0
12.5
10.0
7.5
5.0
2.5
0
– 45
– 25
35
15
–5
55
TEMPERATURE (°C)
75
1536 G02
V
CCA
Input Current
vs Input Voltage
3
2
1
0
–1
–2
–3
0.8 0.85 0.9 0.95 1.0 1.05 1.1 1.15 1.2
INPUT VOLTAGE (V)
1536 G03
T
A
= 25°C
V
CC3
Threshold Voltage
vs Temperature
3.010
3.005
3.000
2.995
2.990
2.985
2.980
2.975
2.970
2.965
2.960
– 60 – 40 – 20
0
20
40
60
80
100
1.005
1.004
1.003
1.002
1.001
1.000
0.999
0.998
0.997
0.996
V
CCA
Threshold Voltage
vs Temperature
TEMPERATURE (°C)
1536 G05
0.995
– 60 – 40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
1536 G06
“Soft” Reset Pulse Width
vs Temperature
2.25
2.20
2.15
2.10
2.05
2.00
1.95
PBR Assertion Time to Reset
vs Temperature
75
100
1536 G07
95.0
– 50
– 25
50
25
0
TEMPERATURE (°C)
75
100
1536 G08
1.90
– 50
– 25
50
25
0
TEMPERATURE (°C)
75
100
1536 G09
LTC1536
TYPICAL PERFORMANCE CHARACTERISTICS
V
CC3
Typical Transient Duration
vs Reset Comparator Overdrive
50
45
TYPICAL TRANSIENT DURATION (µs)
TYPICAL TRANSIENT DURATION (µs)
TYPICAL TRANSIENT DURATION (µs)
45
40
35
30
25
20
15
10
5
RESET OCCURS
ABOVE CURVE
0
0.001
0.01
0.1
1
V
CC3
RESET COMPARATOR OVERDRIVE, V
RT3
– V
CC3
(V)
1536 G10
RST Output Voltage
vs Supply Voltage
5.0
4.5
RST OUTPUT VOLTAGE (V)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE, V
CC
(V)
1536 G13
RST OUTPUT VOLTAGE (V)
V
CC5
= V
CC3
= V
CCA
4.7k PULL-UP FROM RST TO V
CC5
T
A
= 25°C
Undervoltage Response Time
vs Temperature
VOLTAGE (500mV/DIV)
85° – 40°
25°
t
FAIL
SPEC
MARGIN
V
CC3
FALLING
FROM 3.3V TO
2.3V AT (– 0.1V/µs)
TIME (1µs/DIV)
1536 G15
VOLTAGE (1V/DIV)
U W
V
CC5
Typical Transient Duration
vs Reset Comparator Overdrive
40
RESET OCCURS
ABOVE CURVE
35
30
25
20
15
10
5
40
35
30
25
20
15
10
5
0
0.01
0.1
1
0.001
V
CC5
RESET COMPARATOR OVERDRIVE, V
RT5
– V
CC5
(V)
1536 G11
V
CCA
Typical Transient Duration
vs Reset Comparator Overdrive
RESET OCCURS
ABOVE CURVE
0
0.01
0.1
1
0.001
V
CCA
RESET COMPARATOR OVERDRIVE, V
RTA
– V
CCA
(V)
1536 G12
RST Output Voltage
vs Supply Voltage
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE, V
CC
(V)
1536 G16
V
CC5
= V
CC3
= V
CCA
RST PIN LOADED WITH
10MΩ TO GND
T
A
= 25°C
Power-Fail Response Time
vs Temperature
DEVICE THRESHOLD
PCI SPEC
V
CC3
V
CC5
85°
– 40°
25°
RST
RST
TIME (20ns/DIV)
1536 G14
5
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