FeaTures
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LTC2924
Quad Power Supply
Sequencer
DescripTion
The LTC
®
2924 is a power supply sequencer designed for
use with external N-channel MOSFETs or power supplies
with shutdown pins. Four power supplies can be fully
sequenced by a single LTC2924 and up to five supplies
can be sequenced to a sixth master supply. The LTC2924
requires a minimum of external components, using only
two feedback resistors per sequenced power supply and
a single resistor to set hysteresis.
An internally regulated charge pump provides gate drive
voltages for external logic and sub-logic-level MOSFETs.
Adding a single capacitor enables an adjustable time delay
between power supplies during both Power On and Power
Off sequencing. A second capacitor can be added to enable
a power good timer for detecting the failure of any power
supply to turn on within the selected time. Errors in power
supply sequencing and the control input are detected and
reported at the
FAULT
output. The LTC2924 features pre-
cision input comparators which can provide 1% accuracy
in monitoring power supply voltages.
Multiple LTC2924s may be easily cascaded to sequence a
virtually unlimited number of power supplies.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
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Fully Sequence and Monitor Four Supplies
– Six with Minimal External Circuitry
Cascadable for Additional Supplies
Power Off in Reverse Order or Simultaneously
Charge Pump Drives External MOSFETs
Drives Power Supply Shutdown Pins with No
External Pull-Up Resistors
10µA Output Current Allows Soft-Starting of Supplies
Done Indicator for Both Power On and Power Off
Adjustable Time Delay Between Power Supplies
Power Good Timer
Power Supply Voltage Monitoring and Power
Sequence Error Detection and Reporting
Available in a 16-Lead Narrow SSOP Package
applicaTions
n
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Sequenced Power Supplies for ASICs with Multiple
I/O and Core Voltages
Latch-Up Prevention in Systems with Multiple Power
Supplies
Typical applicaTion
3.3V
SHDN
1V
Q2
V
ON
= 2.64V
V
OFF
= 1.98V
V
ON
= 0.93V
V
OFF
= 0.915V
V
ON
= 3.97V
V
OFF
= 2.97V
V
ON
= 2.79V
V
OFF
= 2.73V
V
CC
OUT1
5V EARLY
10k
SYSTEM
CONTROLLER
10k
OUT2
OUT3
OUT4
ON LTC2924
DONE
FAULT
TMR
150nF
150nF
PGT
HYS/CFG
GND
49.9k
Q1-Q4: IRL3714S
ALL RESISTORS 1%
5V/DIV
2V/DIV
5V/DIV
2924 TA01a
Power-Up Sequence
2V/DIV
5V
3.3V
3V
1V
5V/DIV
2V/DIV
5V/DIV
10ms/DIV
2924 TA01b
5V
3V
5V
SHDN
Q1
DONE
TMR
ON
0.1µF
6.04k
IN1
IN2
IN3
IN4
1.69k
100k
1.62k
66.5k
Power-Down Sequence
2V/DIV
18.2k
3.09k
20k
5V
3.3V
3V
1V
DONE
TMR
ON
10ms/DIV
2924 TA01c
2924fb
1
LTC2924
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
IN1
IN2
IN3
IN4
OUT1
OUT2
OUT3
OUT4
1
2
3
4
5
6
7
8
16 ON
15 HYS/CFG
14 TMR
13 GND
12 PGT
11 V
CC
10
DONE
9
FAULT
Supply Voltage (V
CC
) ................................ –0.3V to 6.5V
Input Voltages
ON, IN1-IN4 .................................–0.3V to V
CC
+ 0.3V
PGT, TMR, HYS/CFG ....................–0.3V to V
CC
+ 0.3V
Open-Drain Output Voltages
FAULT, DONE
...............................–0.3V to V
CC
+ 0.3V
Output Voltages
(OUT1 - OUT4) (Note 5) .............. –0.3V to V
CC
+ 4.5V
Operating Temperature Range
LTC2924C ................................................ 0°C to 70°C
LTC2924I .............................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W
orDer inForMaTion
LEAD FREE FINISH
LTC2924CGN#PBF
LTC2924IGN#PBF
LEAD BASED FINISH
LTC2924CGN
LTC2924IGN
TAPE AND REEL
LTC2924CGN#TRPBF
LTC2924IGN#TRPBF
TAPE AND REEL
LTC2924CGN#TR
LTC2924IGN#TR
PART MARKING
2924
2924I
PART MARKING
2924
2924I
PACKAGE DESCRIPTION
16-Lead Plastic SSOP
16-Lead Plastic SSOP
PACKAGE DESCRIPTION
16-Lead Plastic SSOP
16-Lead Plastic SSOP
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
2924fb
2
LTC2924
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3V to 6V, unless otherwise noted.
SYMBOL
Supply
V
CC
I
CC
ON Threshold
V
ON(TH)
V
OFF(TH)
V
ON(TH)
V
OFF(TH)
V
FAULT
I
ON(HYS)
I
ON(ERROR)
I
LEAK
V
ON(HYS)
V
OUT(EN)
I
OUT(EN)
R
OUT(OFF)
R
HYS
V
HYS
ON, Low to High Threshold
ON, High to Low Threshold
IN1-IN4 Low to High Threshold
IN1-IN4 High to Low Threshold
ON, IN1-IN4 High Speed Low Fault Threshold
ON, IN1-IN4 Hysteresis Current Range
ON, IN1-IN4 Hysteresis Current Error
V
ON
≥ V
ON(TH)
(Note 2)
1 – (I
ON(HYS)
/(0.5/R
HYS
)), V
ON(TH)
= 1V
0.5µA ≤ I
ON
< 25µA
25µA ≤ I
ON
≤ 50µA
V
ON(TH)
= 0.5V
I
HYS
• R
IN
(Note 6)
I
OUTn
= 0
OUTn On, V
OUT
= (V
CC
+ 4V)
OUTn Off, I
OUT
= 2mA
(Notes 2, 3)
R
HYS
Tied to GND
R
HYS
Tied to V
CC
Timer On, V
TMR
≤ 0.9V
V
CC
= 5V
Power Good Timer On, V
PGT
≤ 0.9V
V
CC
= 5V
l
l
l
l
l
l
elecTrical characTerisTics
PARAMETER
Input Supply Range
Input Supply Current
CONDITIONS
l
l
MIN
3
TYP
MAX
6
UNITS
V
mA
V
V
V
V
V
µA
%
%
nA
mV
1.5
0.6000
0.6014
0.6020
0.6026
0.33
0.5
0.6060
0.6074
0.6081
0.6087
0.4
3
0.6121
0.6135
0.6142
0.6148
0.48
50
±22
±10
IN1-IN4 Threshold
l
l
ON, IN1-IN4 Characteristics
l
l
l
l
l
l
ON, IN1-IN4 Leakage (Below Threshold)
ON, IN1-IN4 Minimum Hysteresis Voltage
OUT1-OUT4 Gate Drive Voltage
OUT1-OUT4 On Current
OUT1-OUT4 Off Resistance to GND
HYS Current Programming Resistor Range
HYS Programming Voltage
2
4
V
CC
+ 4.5
8.6
10
±100
OUT1-OUT4 Characteristics
V
CC
+ 6
11.2
240
10k
0.5
V
CC
– 0.5
4
0.93
4
0.93
5
1
5
1
6
1.07
6
1.07
1M
V
µA
Ω
Ω
V
V
µA
V
µA
V
HYS Characteristics
TMR Characteristics
I
TMR
V
TH(HI)
I
PGT
V
PGT
Timer Pin Output Current
Timer High Voltage Threshold
Power Good Timer Pin Output Current
Power Good Timer Fault Detected Voltage
Threshold
PGT Characteristics
2924fb
3
LTC2924
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3V to 6V, unless otherwise noted.
SYMBOL
R
D(LO)
I
D(HI)
R
FAULT (LO)
I
FAULT(HI)
V
FAULT(HI)
V
FAULT(LO)
R
F(EXT)
t
FAULT
t
FAULT(MIN)
PARAMETER
DONE
Pin Pull-Down Resistance to GND
DONE
Pin Off Leakage Current
FAULT
Pin Pull-Down Resistance to GND
FAULT
Pin Off Leakage Current
Voltage Above Which an Externally Generated
FAULT Condition Will Not be Detected
Voltage Below Which an Externally Generated
FAULT Condition Will be Detected
External Pull-Up Resistance
Externally Commanded FAULT Below V
FAULT(LO)
to OUT1-OUT4 Pull-Down On Delay
Externally Commanded FAULT Minimum Time
Below V
FAULT(LO
)
(Note 4)
l
l
elecTrical characTerisTics
DONE
Characteristics
CONDITIONS
DONE
= Low, I = 2mA
DONE
= High
FAULT
Being Pulled Low Internally,
I = 2mA
FAULT
High
l
l
MIN
TYP
MAX
100
15
400
2
UNITS
Ω
µA
Ω
µA
V
FAULT
Characteristics
l
l
l
l
1.6
0.6
10
1
1
V
kΩ
µs
µs
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 2:
Hysteresis current must be 500nA minimum. Hysteresis current
may exceed 50µA, but accuracy is not guaranteed.
Note 3:
HYS/CFG pin must be pulled to GND or V
CC
with an external
resistor. See Applications Information for details.
Note 4:
Determined by design, not production tested. External circuits
pulling down on the
FAULT
pin must maintain the signal below V
FAULT(LO)
for ≥1µs.
Note 5:
Internal circuits may drive the OUTn pins higher than the Absolute
Maximum Ratings.
Note 6:
R
IN
is the parallel combination of the two resistors forming the
resistive divider connected to the ON and IN1-IN4 pins.
2924fb
4
LTC2924
Typical perForMance characTerisTics
2.3
2.1
1.9
V
OUT
(V)
I
CC
(mA)
1.7
1.5
1.3
1.1
0.9
3
3.5
4
ON LOW
ON HIGH
I
CC
vs V
CC
I
OUT1-4
= –10µA
R
HYS
= 51k
14
12
10
V
OUT(EN)
vs I
OUT
12
V
CC
= 6V
11
V
OUT(EN)
vs V
CC
I
OUT1-4
< 1µA
6
4
2
V
OUT
(V)
ONE OUTPUT DRIVING CURRENT
0
2
4
6
I
OUT
(µA)
8
10
12
2924 G02
8
V
CC
= 3V
10
9
8
4.5
V
CC
(V)
5
5.5
6
2924 G01
0
7
2
3
4
V
CC
(V)
5
6
2924 G03
R
DONE
vs V
CC
55
50
R
FAULT
AT 2mA ( )
R
DONE
AT 2mA ( )
200
180
160
140
120
100
80
R
FAULT
vs V
CC
45
40
35
30
3
4
V
CC
(V)
5
6
2924 G04
3
4
V
CC
(V)
5
6
2924 G05
45
40
35
I
SAT
(mA)
30
25
20
15
OUTn (Off) I
SAT
vs Temperature
V
OUT
= 5V
V
CC
= 6V
I
SAT
(mA)
35
OUTn (Off) I
SAT
vs V
CC
V
OUT
= 5V
30
25
20
V
CC
= 3V
15
10
2.5
10
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
80
100
3
3.5
4
4.5
V
CC
(V)
5
5.5
6
6.5
2924 G06
2924 G07
2924fb
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