FeaTures
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LTC2928
Multichannel Power Supply
Sequencer and Supervisor
DescripTion
The
LTC
®
2928
is a four channel cascadable power
supply sequencer and high accuracy supervisor. Sequenc-
ing thresholds, order and timing are configured with just a
few external components, negating the need for PC board
layout or software changes during system development.
Multiple LTC2928s may be easily connected to sequence
an unlimited number of power supplies.
Sequence outputs control supply enable pins or
N-channel pass gates. Precision input comparators with
individual outputs monitor power supply voltages to 1.5%
accuracy. Supervisory functions include undervoltage
and overvoltage monitoring and reporting as well as
µP
reset generation.
RST
may be forced high to complement
margin testing.
Application faults, whether internally or externally gener-
ated, can shut down all controlled supplies. The type and
source of faults are reported for diagnosis. Individual
channel controls are available to independently exercise
enable outputs and supervisory functions.
A high voltage input allows the LTC2928 to be powered
from voltages as high as 16.5V. A buffered reference
output permits single negative power supply sequencing
and monitoring operations.
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Easily Configure Power Management
without Software
Controls Up to Four Supplies per Device
Cascades for Additional Supplies
Staged Supply Sequencing with
Adjustable Time Positions
Fault Event Reporting with Diagnostics
Selectable System Shutdown on Fault
1.5% Undervoltage Monitor Accuracy
Overvoltage and/or Fault Indication
Configurable Undervoltage and
Overvoltage Thresholds
Charge Pumped Enable Pins Drive N-Channel MOS-
FETs
Operates from 2.9V to 16.5V
5mm
×
7mm 38-lead QFN and
36-lead SSOP Packages
Network/Telecom Infrastructure
Sequencing for Multiple I/O and Core Voltages
Power Management
applicaTions
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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.
Protected by U.S. Patents, including 4843302, 6949965.
Typical applicaTion
12V
LTM4600
V
IN
V
OUT
RUN
10k
V
IN
LTC3414
V
OUT
3.3V
1.2V
LTC1628
V
IN
V
OUT
RUN
AUSTIN LYNX
V
IN
V
OUT
AXA010AY93
0.1µF
ON
95.3k
24.3k
9.53k
1.5k
3.4k
RUN
2.5V
Sequencing Up and Down
3.3V
2.5V
1.8V
1.2V
Si7894ADP
1.8V
12.1k
23.2k
36.5k
51.1k
1V/DIV
ON
100
HV
CC
EN2
EN1 EN4
EN3
1µF
ON
RT1
RT2
RT3
RT4
DONE
V
CC
GND MS1 VSEL
V1
V2
V3
LTC2928
V4
RST
OV
FLT
RTMR PTMR STMR
0.047µF
3300pF
10k
10k
10k
10k
DONE
SYSTEM
RESET
FAULT
START
SEQUENCE SEQUENCE UP
START
UP COMPLETE
SEQUENCE
DOWN
SEQUENCE
DOWN
COMPLETE
2928 TA07
ALL RESISTORS 1%
2928 TA06
2928fa
For more information
www.linear.com/LTC2928
1
LTC2928
absoluTe MaxiMuM raTings
(Note 1)
Supply Voltages
HV
CC
...................................................... –0.3V to 18V
V
CC
........................................................ –0.3V to 6.5V
Input Voltages
V1, V2, V3, V4 .........................................–0.3V to 12V
MS1, MS2, RDIS ................................... –0.3V to 6.5V
SQT1, SQT2, VSEL ............................... –0.3V to 6.5V
RT1, RT2, RT3, RT4 .............................. –0.3V to 6.5V
ON, OVA .........................................–0.3 to V
CC
+ 0.3V
STMR, PTMR, RTMR.....................–0.3 to V
CC
+ 0.3V
Output Voltages
EN1, EN2, EN3, EN4 (Note 3) ..................–0.3V to 12V
CMP1, CMP2, CMP3, CMP4.................. –0.3V to 6.5V
FLT, RST, OV,
CAS ................................ –0.3V to 6.5V
DONE,
REF ...................................–0.3V to V
CC
+ 0.3V
RMS Currents
IV
CC
................................................................. ±10mA
IHV
CC
.............................................................. ±20mA
I
REF
.................................................................. ±10mA
Operating Ambient Temperature Range
LTC2928C ................................................ 0°C to 70°C
LTC2928I .............................................–40°C to 85°C
Storage Temperature Range
SSOP Package ................................... –65°C to 150°C
QFN Package ..................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
SSOP Package .................................................. 300°C
pin conFiguraTion
TOP VIEW
CMP2
CMP1
CMP4
CMP3
CMP1
CMP2
EN2
V2
OVA
EN1
V1
REF
RT1
1
2
3
4
5
6
7
8
9
36 CMP4
EN2
V2
35 CMP3
34 V3
33 EN3
32 V4
31 EN4
30 RTMR
29 PTMR
28 STMR
27 VSEL
26 GND
25 HV
CC
24 V
CC
23 RST
22 OV
21 FLT
20 DONE
19 ON
OVA 1
EN1 2
V1 3
N/C 4
REF 5
RT1 6
RT2 7
RT3 8
RT4 9
SQT1 10
SQT2 11
MS1 12
13 14 15 16 17 18 19
MS2
RDIS
CAS
ON
N/C
DONE
FLT
39
TOP VIEW
V3
31 EN3
30 V4
29 EN4
28 RTMR
27 PTMR
26 STMR
25 VSEL
24 GND
23 HV
CC
22 V
CC
21
RST
20
OV
38 37 36 35 34 33 32
RT2 10
RT3 11
RT4 12
SQT1 13
SQT2 14
MS1 15
MS2 16
RDIS 17
CAS 18
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 39) PCB GND CONNECTION OPTIONAL
G PACKAGE
36-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
2
2928fa
For more information
www.linear.com/LTC2928
LTC2928
orDer inForMaTion
LEAD FREE FINISH
LTC2928CG#PBF
LTC2928IG#PBF
LTC2928CUHF#PBF
LTC2928IUHF#PBF
TAPE AND REEL
LTC2928CG#TRPBF
LTC2928IG#TRPBF
LTC2928CUHF#TRPBF
LTC2928IUHF#TRPBF
PART MARKING
LTC2928CG
LTC2928IG
LTC2928CUHF
LTC2928IUHF
PACKAGE DESCRIPTION
36-Lead Plastic SSOP (5.3mm)
36-Lead Plastic SSOP (5.3mm)
38-Lead (5mm
×
7mm) Plastic QFN
38-Lead (5mm
×
7mm) Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.3V unless otherwise noted.
SYMBOL
V
VCC
I
VCC
V
UVL
V
UVL(HYST)
V
HVCC
V
CC(REG)
I
REG
I
HVCC
V
ON
V
ON(HYST)
I
ON(LKG)
V
MON(TH)
V
SEQ(TH)
PARAMETER
V
CC
Input Supply Range
V
CC
Input Supply Current
V
CC
Input Supply Undervoltage Lockout
Undervoltage Lockout Hysteresis
High Voltage Input Supply Range
Regulated V
CC
from HV
CC
Regulated V
CC
Output Current to
External Load (Note 2)
HV
CC
Input Supply Current
ON Threshold Voltage
ON Hysteresis
ON Leakage Current
Reset Threshold Voltage
V1 Negative Threshold Voltage
Sequencing Thresholds
0.67 V
MON(TH)
0.33 V
MON(TH)
0.10 V
MON(TH)
Monitor Pin Leakage Current
Undervoltage Pulse Width Required to
Trip Comparators
Overvoltage Pulse Width Required to
Trip
OV
V
ON
= 1V
I
REG
= 0mA, V
HVCC
= 12V
V
ON
Rising
V
HVCC
= 12V
HV
CC
= GND
V
CC
Rising
CONDITIONS
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elecTrical characTerisTics
Supply Pins: V
CC
, HV
CC
MIN
2.9
TYP
MAX
6
UNITS
V
mA
V
mV
V
V
mA
mA
V
mV
nA
V
mV
V
V
V
nA
µs
µs
1
2.75
50
7.2
3.2
2.8
100
12
3.3
2.5
2.85
150
16.5
3.4
–10
1
0.985
20
1.00
30
2
1.015
40
±50
Sequence Up/Down Pin: ON
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Voltage Monitor Pins: V1, V2, V3, V4
VSEL = V
CC
See Table 4
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0.4925
0.500
0.5075
±18
0.351
0.185
0.068
±15
0.315
0.149
0.032
0.333
0.167
0.05
225
225
I
MON(LKG)
t
MON(UV)
t
MON(OV)
V
MON
= 0.55V
V
MON
below V
MON(TH)
by 1%
V
MON
above Overvoltage Threshold by
1%
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2928fa
For more information
www.linear.com/LTC2928
3
LTC2928
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.3V unless otherwise noted.
SYMBOL
V
EN
I
EN(UP)
V
EN(OL)
V
CMP(OL)
V
CMP(OH)
PARAMETER
Enable Pin Voltage Output in On State
Enable Pin Pull-Up Current
Enable Pin Voltage Output Low
Comparator Voltage Output Low
Comparator Voltage Output High
(Note 4)
Voltage Input Low Threshold
Voltage Input High Threshold
High Z Pin Current
V
HZ
= 0.7V
V
HZ
= 1.1V
CONDITIONS
I
EN
= –1µA
Enable Pin On, V
EN
≤ (V
CC
+ 4V)
I
EN
= 2.5mA
I
CMP
= 2.5mA
I
CMP
= –1µA
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elecTrical characTerisTics
MIN
V
CC
+ 4.5
–7.5
TYP
V
CC
+
5.5
–10
0.25
0.15
MAX
V
CC
+ 6
–12.5
0.4
0.3
UNITS
V
µA
V
V
V
Supply Enable Pins: EN1, EN2, EN3, EN4
Comparator Outputs: CMP1, CMP2, CMP3, CMP4
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V
CC
– 1
Three-State Selection Inputs: SQT1, SQT2, MS1, MS2, RDIS
V
IL
V
IH
I
HZ
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0.4
1.4
–10
10
0.4
1.4
0.045
•
V
CC
V
V
µA
µA
V
V
V
V
Positive/Negative Selection Input: VSEL
V
IL
V
IH
V
RT(LO)
V
RT(HI)
R
RT
Cascade Pin: CAS
V
CAS(OL)
I
CAS(UP)
t
CAS(HI)
t
CAS(MIN)
Fault Status Pin:
FLT
V
FLT(OL)
I
FLT(UP)
V
FLT(TH)
V
FLT(HYST)
t
FLT
I
FLT(LKG)
V
DONE(OL)
FLT
Voltage Output Low
FLT
Pull-Up Current
External Fault Input Threshold
External Fault Input Hysteresis
Minimum Detectable External Fault
Pulse Width
Fault Pin Leakage Current
DONE
Voltage Output Low
V
FLT
= V
CC
I
DONE
= 2.5mA
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Voltage Input Low Threshold
Voltage Input High Threshold
Voltage Required to Force Enable Pin
Low While Sequencing
Voltage Required to Force Enable Pin
High Outside of Sequencing
R
T
Pin Input Resistance
CAS Voltage Output Low
CAS Pull-Up Current
Fixed Time Delay between Sequence
Time Positions (Note 5)
Minimum CAS Low Time During
Sequencing
I
FLT
= 2.5mA
V
FLT
= V
CC
–1V
V
FLT
Falling
I
CAS
= 2.5mA
Master Pulling CAS High, V
CAS
= GND
CAS High, C
STMR
= 1500pF
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Sequence Time Position Control Inputs: RT1, RT2, RT3, RT4 (see resistor selection Table 3)
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0.955
•
V
CC
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11.2
12
0.15
12.8
0.3
–75
15
30
kΩ
V
µA
ms
µs
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–45
11
15
–60
13
22.5
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0.15
–12
1.0
25
–17
1.1
100
0.3
–22
1.2
150
2
±1
V
µA
V
mV
µs
µA
V
Done Status Pin:
DONE
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0.15
0.3
4
2928fa
For more information
www.linear.com/LTC2928
LTC2928
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.3V unless otherwise noted.
SYMBOL
I
DONE(DN)
R
DONE
V
DONE(LAST)
Reset Pin:
RST
V
RST(OL)
RST
Voltage Output Low
V
CC
= 0.2V, I
RST
= 0.1µA
V
CC
= 0.5V, I
RST
= 5µA
V
CC
= 1V, I
RST
= 200µA
V
CC
= 3V, I
RST
= 2500µA
I
RST
= –1µA (Note 7)
V
TMR
= GND
V
TMR
= 1.3V
C
RTMR
= 1500pF
C
PTMR
= 1500pF
C
STMR
= 1500pF
I
REF
= 0.2mA, –1mA, C
REF
= ≤ 1000pF
VSEL = V
CC
VSEL = V
CC
VSEL = V
CC
VSEL = V
CC
I
OV
= 2.5mA
I
OV
= –1µA
OV
Low Time Upon Cleared
OV Event, C
RTMR
= 1500pF
V
OVA
= GND
V
OVA
Floating
V
OVA
= V
CC
= 3.3V
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elecTrical characTerisTics
PARAMETER
DONE
Pull-Down Current
Required Pull-Up Resistance on “Last”
LTC2928
Voltage Output High when Configured
as “Last”
CONDITIONS
V
DONE
= 3.3V (Note 6)
5% Tolerance or Better
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MIN
2.4
0.8
•
V
CC
TYP
20
MAX
40
5.1
UNITS
µA
kΩ
V
5
10
25
150
V
CC
– 1
–1.7
15
5
5
11
1.172
1.172
0.780
0.386
0.109
–2
20
6
6
13
1.189
1.189
0.793
0.396
0.119
0.15
V
CC
– 1
5
6
60
150
300
300
mV
mV
mV
mV
V
V
RST(OH)
I
TMR(UP)
I
TMR(DN)
t
RTMR
t
PTMR
t
STMR
V
REF
RST
Voltage Output High
Timer Pull-Up Current
Timer Pull-Down Current
Timer Period, RTMR (Note 8)
Timer Period, PTMR
Timer Period, STMR
Reference Voltage Output
100% Sequence Threshold
67% Sequence Threshold
33% Sequence Threshold
10% Sequence Threshold
OV
Voltage Output Low
OV
Voltage Output High (Note 7)
OV
Indication Time (Note 8)
Timer Pins: RTMR, PTMR, STMR
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–2.3
25
7
7
15
1.205
1.205
0.806
0.406
0.129
0.3
7
µA
µA
ms
ms
ms
V
V
V
V
V
V
V
ms
External Voltage Reference Pin: REF
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Over Voltage Indication Pin:
OV
V
OV(OL)
V
OV(OH)
t
OV
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Over Voltage Adjust Pin: OVA
V
OVA(TH)
Over Voltage Threshold at Comparator
Inputs (Note 9)
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0.546
0.650
1.042
0.556
0.660
1.072
0.566
0.670
1.102
V
V
V
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:
All currents into pins are positive, all voltages are referenced to
GND unless otherwise noted.
Note 3:
Internal circuits regulate the EN output voltage to V
EN
. Driving this
pin to voltages beyond V
EN
may damage the part.
Note 4:
The comparator outputs have internal pull-ups to V
CC
of typically
–10µA. However, external pull-up resistors may be used when faster rise
times are required or for V
OH
voltages greater than V
CC
.
Note 5:
The CAS high time after an ON edge is stretched by the ON pin
propagation delay (20µs typical).
Note 6:
The
DONE
pull-down current is present when
DONE
is high to
facilitate cascading multiple LTC2928s.
Note 7:
The
RST
and
OV
outputs have an internal pull-up to V
CC
of
typically –10µA. However, external pull-up resistors may be used when
faster rise times are required or for V
OH
voltages greater than V
CC
.
Note 8:
If the termination of under and overvoltage events occur within
one nominal t
RTMR
period, the variation in t
RTMR
and/or t
OV
may be ±15%.
Note 9:
Use a resistor from OVA to ground or V
CC
to configure overvoltage
thresholds within the max/min ranges shown. See Applications
Information for details.
2928fa
For more information
www.linear.com/LTC2928
5
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