LTC2924
Quad Power Supply
Sequencer
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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
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
F
A
U
L
T 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
APPLICATIO S
■
■
Sequenced Power Supplies for ASICs with Multiple
I/O and Core Voltages
Latch-Up Prevention in Systems with Multiple Power
Supplies
3.3V
SHDN
1V
Q2
5V
5V
SHDN
3V
Q1
V
CC
OUT1
IN1
IN2
IN3
IN4
5V EARLY
10k
SYSTEM
CONTROLLER
10k
150nF
150nF
U
TYPICAL APPLICATIO
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
6.04k
100k
1.62k
66.5k
2V/DIV
5V/DIV
2V/DIV
5V/DIV
10ms/DIV
2924 TA01b
0.1µF
OUT2
OUT3
OUT4
ON LTC2924
DONE
FAULT
TMR
PGT
2V/DIV
1.69k
18.2k
3.09k
20k
5V/DIV
HYS/CFG
GND
49.9k
Q1-Q4: IRL3714S
ALL RESISTORS 1%
2V/DIV
5V/DIV
2924 TA01a
U
Power-Up Sequence
5V
3.3V
3V
1V
DONE
TMR
ON
FEATURES
DESCRIPTIO
U
Power-Down Sequence
5V
3.3V
3V
1V
DONE
TMR
ON
10ms/DIV
2924 TA01c
2924fa
1
LTC2924
(Note 1)
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
F
A
U
L
T,
D
O
N
E .............................. –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
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
ORDER PART
NUMBER
LTC2924CGN
LTC2924IGN
GN PART
MARKING
2924
2924I
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
ELECTRICAL CHARACTERISTICS
The
●
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
PARAMETER
CONDITIONS
Supply
V
CC
Input Supply Range
I
CC
Input Supply Current
ON Threshold
V
ON(TH)
ON, Low to High Threshold
V
OFF(TH)
ON, High to Low Threshold
IN1-IN4 Threshold
V
ON(TH)
IN1-IN4 Low to High Threshold
V
OFF(TH)
IN1-IN4 High to Low Threshold
ON, IN1-IN4 Characteristics
V
FAULT
ON, IN1-IN4 High Speed Low Fault Threshold
I
ON(HYS)
ON, IN1-IN4 Hysteresis Current Range
V
ON
≥ V
ON(TH)
(Note 2)
I
ON(ERROR)
ON, IN1-IN4 Hysteresis Current Error
1 – (I
ON(HYS)
/(0.5/R
HYS
)), V
ON(TH)
= 1V
0.5µA ≤ I
ON
< 25µA
25µA ≤ I
ON
≤ 50µA
I
LEAK
ON, IN1-IN4 Leakage (Below Threshold)
V
ON(TH)
= 0.5V
V
ON(HYS)
ON, IN1-IN4 Minimum Hysteresis Voltage
I
HYS
• R
IN
(Note 6)
OUT1-OUT4 Characteristics
V
OUT(EN)
OUT1-OUT4 Gate Drive Voltage
I
OUT(EN)
OUT1-OUT4 On Current
R
OUT(OFF)
OUT1-OUT4 Off Resistance to GND
HYS Characteristics
R
HYS
HYS Current Programming Resistor Range
V
HYS
HYS Programming Voltage
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
MIN
●
●
●
●
●
●
●
●
●
●
●
●
TYP
MAX
6
3
0.6121
0.6135
0.6142
0.6148
0.48
50
±22
±10
±100
UNITS
V
mA
V
V
V
V
V
µA
%
%
nA
mV
V
µA
Ω
Ω
V
V
2924fa
3
1.5
0.6000
0.6014
0.6020
0.6026
0.33
0.5
0.6060
0.6074
0.6081
0.6087
0.4
2
4
V
CC
+ 4.5
8.6
●
●
10
V
CC
+ 6
11.2
240
1M
10k
0.5
VCC – 0.5
2
U
W
U
U
W W
W
ABSOLUTE
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
LTC2924
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
TMR Characteristics
I
TMR
Timer Pin Output Current
V
TH(HI)
Timer High Voltage Threshold
PGT Characteristics
I
PGT
Power Good Timer Pin Output Current
V
PGT
Power Good Timer Fault Detected
Voltage Threshold
D
O
N
E Characteristics
D
O
N
E Pin Pull-Down Resistance to GND
R
D(LO)
D
O
N
E Pin Off Leakage Current
I
D(HI)
F
A
U
L
T Characteristics
R
FAULT (LO)
FAULT Pin Pull-Down Resistance to GND
I
FAULT(HI)
V
FAULT(HI)
V
FAULT(LO)
R
F(EXT)
t
FAULT
t
FAULT(MIN)
F
A
U
L
T Pin Off Leakage Current
The
●
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.
CONDITIONS
Timer On, V
TMR
≤ 0.9V
V
CC
= 5V
Power Good Timer On, V
PGT
≤ 0.9V
V
CC
= 5V
●
MIN
4
0.93
4
0.93
TYP
5
1
5
1
MAX
6
1.07
6
1.07
UNITS
µA
V
µA
V
●
DO
N
E = Low, I = 2mA
D
O
N
E = High
FA
U
L
T Being Pulled Low Internally,
I = 2mA
F
A
U
L
T High
●
●
●
●
●
●
●
●
100
15
400
2
1.6
0.6
10
1
1
Ω
µA
Ω
µA
V
V
kΩ
µs
µs
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
(Note 4)
Below V
FAULT(LO
)
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
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
F
A
U
L
T 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.
TYPICAL PERFOR A CE 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
6
4
2
V
OUT
(V)
4.5
V
CC
(V)
5
U W
5.5
14
12
10
8
V
OUT(EN)
vs I
OUT
V
CC
= 6V
12
11
V
OUT(EN)
vs V
CC
I
OUT1-4
< 1µA
V
CC
= 3V
10
9
8
ONE OUTPUT DRIVING CURRENT
0
2
4
6
I
OUT
(µA)
8
10
12
2924 G02
6
2924 G01
0
7
2
3
4
V
CC
(V)
5
6
2924 G03
2924fa
3
LTC2924
TYPICAL PERFOR A CE CHARACTERISTICS
55
50
R
FAULT
AT 2mA (Ω)
5
V
CC
(V)
2924 G04
R
DONE
vs V
CC
R
DONE
AT 2mA (Ω)
45
40
35
30
3
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)
10
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
4
U W
4
200
180
160
140
120
100
80
R
FAULT
vs V
CC
6
3
4
V
CC
(V)
5
6
2924 G05
35
OUTn (Off) I
SAT
vs V
CC
V
OUT
= 5V
30
25
20
V
CC
= 3V
15
10
2.5
80
100
3
3.5
4
4.5
V
CC
(V)
5
5.5
6
6.5
2924 G06
2924 G07
2924fa
LTC2924
PI FU CTIO S
IN1-IN4 (Pins 1, 2, 3, 4):
Sequenced Power Supply Moni-
tor Input. Connect this pin to an external resistive divider
between each sequenced power supply and GND. During
Power On sequencing, 0.61V (typ) at this pin indicates
that the sequenced power supply (enabled with each of
the OUT1-OUT4 pins) has reached the desired Power On
sequence voltage. A hysteresis current (programmed by
the HYS pin) is sourced out of each of the IN1-IN4 pins
after the 0.61V threshold is detected. During the Power Off
sequence, 0.61V at this pin indicates that the sequenced
power supply has reached the desired Power Off voltage.
The hysteresis current is removed after the 0.61V thresh-
old is detected.
OUT1-OUT4 (Pins 5, 6, 7, 8):
Sequenced Power Supply
Enable. Connect this pin to the shutdown pin or an external
series N-channel MOSFET gate for each power supply being
sequenced. (A low at this pin means the sequenced power
supply is commanded to turn off.) When disabled, each
output is connected to GND with a resistance of <240Ω.
When enabled, each output is connected to an internally
generated charge pump supply (nominally V
CC
+ 5V) via
an internal 10µA (typ) current source.
F
A
U
L
T (Pin 9):
Fault Pin. Pull this pin high with an external
10k resistor. The LTC2924 will pull this pin low if a fault
condition is detected (see Applications Information for
details). Pulling this pin low externally causes a simulta-
neous unsequenced Power Off.
DO
N
E (Pin 10):
Done Pin. Pull this pin high with an ex-
ternal 10k resistor. This open-drain output pulls low at
the completion of the Power-On sequence. At the end of
the Power Off sequence, the LTC2924 floats this pin. For
cascading multiple LTC2924s, see Application Information
for connecting the
D
O
N
E pin.
V
CC
(Pin 11):
LTC2924 Power Supply Input. All internal
circuits are powered from this pin. V
CC
should be con-
nected to a low noise power supply voltage and should
be bypassed with at least a 0.1µF capacitor to the GND
pin in close proximity to the LTC2924.
U
U
U
PGT (Pin 12):
Power Good Timer. The PGT pin sets the
time allowed for a power supply to turn on after being
enabled with the OUT1-OUT4 pins. Connecting a capacitor
between this pin and ground programs a 200mS/µF dura-
tion. The PGT pin is reset before each of the OUT1-OUT4
pins are asserted. If the voltage at the PGT pin reaches
1V, a fault condition is asserted. The PGT pin must be
connected directly to ground to disable the power good
timer function.
GND (Pin 13):
Ground. All internal circuits are returned to
the GND pin. Connect this pin to the ground of the power
supplies that are being sequenced.
TMR (Pin 14):
Timer. A capacitor connected between
this pin and ground sets the time delay between a supply
ready (IN1-IN4) signal and the enabling of the next power
supply in the sequence (OUT1-OUT4), with a 200mS/µF
duration. The TMR pin may be left floating if no delay is
required between supplies being sequenced on or off. If
an internal fault condition occurs, TMR will indicate so by
going to V
CC
until the fault condition is cleared. Do not
connect any other circuits to the TMR pin.
HYS/CFG (Pin 15):
Hysteresis Current Setting and Cascade
Configuration. Connecting a resistor between this pin and
GND programs a 0.5/R
EXT
(typ) hysteresis current which
is sourced out of each IN and ON pin. When multiple
LTC2924s are cascaded, the HYS/CFG pin is also used to
configure the position of the
first
LTC2924. See Applica-
tions Information for details.
ON (Pin 16):
On Pin. Commands the LTC2924 to sequence
the power supplies up (Power On sequence) or down
(Power Off sequence). Typically connected to a system
controller. Hysteresis current is applied to this pin when
above 0.61V (typ). This pin has a precision 0.61V threshold
and can be used to sense a nonsequenced power supply’s
voltage to start the Power On sequence. See Applications
Information for details. For cascading multiple LTC2924s,
see Applications Information for connecting the ON pin.
2924fa
5
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