19-3771; Rev 1; 10/05
KIT
ATION
EVALU
E
BL
AVAILA
Dual-/Triple-Voltage, Power-Supply
Trackers/Sequencers/Supervisors
General Description
Features
♦
Pin-Selectable Tracking or Sequencing Control
for Up to Three Supply Voltages
♦
Capacitor-Adjustable Power-Up/Down Tracking
Slew Rate
♦
Capacitor-Adjustable Power-Up Sequencing Delay
♦
Internal Charge Pumps to Enhance External
n-Channel FETs
♦
Capacitor-Adjustable Timeout Period Power-Good
Output (MAX6877/MAX6878)
♦
Adjustable Undervoltage Lockout or
Logic-Enable Input
♦
Internal 100Ω Pulldown for Each Output to
Discharge Capacitive Load Quickly
♦
0.5V to 5.5V Nominal IN_/OUT_ Range
♦
2.7V to 5.5V Operating Voltage Range
♦
Immune to Short Voltage Transients
♦
Small 4mm x 4mm 24-Pin or 16-Pin Thin QFN
Packages
MAX6877/MAX6878/MAX6879
The MAX6877/MAX6878/MAX6879 multivoltage power
trackers/sequencers/supervisors monitor up to three
system voltages and provide proper power-up and
power-down control for systems requiring voltage track-
ing or sequencing. These devices ensure controlled
voltage tracking within a specified range or sequencing
in the proper order as system power supplies are
enabled. The MAX6877/MAX6878/MAX6879 generate
all required voltages and timing to control up to three
external n-channel pass FETs for the OUT1/OUT2/
OUT3 supply voltages (see the
Selector Guide
for dif-
ferent features of each device).
The MAX6877/MAX6878/MAX6879 feature adjustable
undervoltage thresholds for each input supply. When all
the voltages are above these adjustable thresholds, the
devices turn on the external n-channel MOSFETs to
either sequence or track the voltages to the system.
During voltage-tracking mode, the voltage at the GATE
of each MOSFET is increased to slowly bring up all
supplies at a controlled slew rate. The MAX6877/
MAX6878/MAX6879 feature an autoretry or latch-off
mode with capacitor-adjusted timing.
These devices also provide a controlled power-down
(tracking mode) when the system shuts off in an orderly
manner. When an unexpected fault occurs, the outputs
are all pulled down simultaneously with an internal
100Ω pulldown to help discharge capactive loads at
the MOSFET’s source. The MAX6877/MAX6878/
MAX6879 feature independent internal charge pumps
to fully enhance the external FETs for low-voltage drop
at highpass current. The MAX6877 and MAX6878 also
feature a power-good output with a selectable timeout
period that can be used for system reset.
The MAX6877/MAX6878/MAX6879 are available in
small 4mm x 4mm 24-pin and 16-pin thin QFN pack-
ages and are fully specified over the -40°C to +85°C
extended operating temperature range.
Ordering Information
PART
MAX6877ETG+
TEMP RANGE
-40°C to +85°C
PIN-
PACKAGE
24 Thin QFN
PKG
CODE
T2444-4
Ordering Information continued at end of data sheet.
+Denotes
lead-free package.
Pin Configurations
OUT2
OUT3
TOP VIEW
18
GATE2 19
OUT1 20
17
16
15
14
13
12
11
10
TRK/SEQ
LTCH/RTR
TIMEOUT
SLEW
DELAY
GND
Applications
Multivoltage Systems
Networking Systems
Telecom
Storage Equipment
Servers/Workstations
GATE1 21
IN3 22
IN2 23
IN1 24
1
V
CC
2
ABP
3
SET3
4
SET2
5
SET1
6
EN/UV
MAX6877
EP*
MARGIN
9
8
7
+
4mm x 4mm THIN QFN
*EXPOSED PADDLE CONNECTED TO GND.
Selector Guide appears at end of data sheet.
Pin Configurations continued at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PG/RST
GATE3
FAULT
Dual-/Triple-Voltage, Power-Supply
Trackers/Sequencers/Supervisors
MAX6877/MAX6878/MAX6879
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
IN1, IN2, IN3, V
CC
....................................................-0.3V to +6V
ABP
.....................................-0.3V to the highest of V
IN1
- V
IN3
or V
CC
SET1, SET2, SET3 ....................................................-0.3V to +6V
GATE1, GATE2, GATE3 .........................................-0.3V to +12V
OUT1, OUT2, OUT3 .................................................-0.3V to +6V
LTCH/RTR, TRK/SEQ, MARGIN
...............................-0.3V to +6V
FAULT,
PG/RST, EN/UV ...........................................-0.3V to +6V
DELAY, SLEW, TIMEOUT .........................................-0.3V to +6V
OUT_ Current....................................................................±50mA
GND Current.....................................................................±50mA
Input/Output Current (all pins except
OUT_ and GND) ...........................................................±20mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin 4mm x 4mm Thin QFN
(derate 16.9mW/°C above +70°C) .............................1349mW
24-Pin 4mm x 4mm Thin QFN
(derate 20.8mW/°C above +70°C) .............................1667mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Maximum Junction Temperature .....................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
, IN1, IN2, or IN3 = +2.7V to +5.5V, EN/UV
=
MARGIN
= ABP, T
A
= -40°C to +85°C, unless otherwise specified. Typical values
are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
Voltage on ABP (the highest of V
CC
or IN_)
to ensure that PG/RST and
FAULT
are valid
and GATE_ = 0V
Voltage on ABP (the highest of V
CC
or IN_)
to ensure the device is fully operational
Supply Current
SET_ Threshold Range
SET_ Threshold Hysteresis
SET_ Input Current
EN/UV Input Voltage
EN/UV Input Current
EN/UV Input Pulse Width
DELAY, TIMEOUT Output Current
DELAY, TIMEOUT Threshold
Voltage
SLEW Output Current (Note 4)
Track/Sequence Slew-Rate
Timebase Accuracy
Timebase/C
SLEW
Ratio
Slew-Rate Accuracy during Power-
Up and Power-Down
Power-Good Threshold
V
TH_PG
I
S
SR
C
SLEW
= 200pF (Note 4)
100pF < C
SLEW
< 1nF (Note 4)
C
SLEW
= 200pF, ABP = 5.5V (Note 4)
V
OUT_
falling
-50
91.5
92.5
I
CC
V
TH
V
TH_HYS
I
SET
V
EN_R
V
EN_F
I
EN
t
EN
I
D
EN/UV falling, 100mV overdrive
(Notes 2, 3)
V
CC
= 3.3V
22.5
-15
104
+50
93.5
V
CC
= 5.5V, IN1 = IN2 = IN3 = 3.3V, no load
SET_ falling, T
A
= +25
o
C
SET_ falling, T
A
= -40 C to +85 C
SET_ rising
SET_ = 0.5V
Input rising
Input falling
1.22
-5
7
2.12
2.5
1.25
25
27.5
+15
2.88
-100
1.286
1.25
1.28
+5
o
o
MIN
1.4
TYP
MAX
UNITS
Operating Voltage Range
V
CC
V
2.7
1.1
0.4925
0.4875
0.5
0.5
0.5
+100
5.5
1.8
0.5075
0.5125
mA
V
%
nA
V
µA
µs
µA
V
µA
%
kΩ
%
%
2
_______________________________________________________________________________________
Dual-/Triple-Voltage, Power-Supply
Trackers/Sequencers/Supervisors
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
, IN1, IN2, or IN3 = +2.7V to +5.5V, EN/UV =
MARGIN
= ABP, T
A
= -40°C to +85°C, unless otherwise specified. Typical values
are at T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Power-Good Threshold Hysteresis
GATE_ Output High
GATE_ Pullup Current
SYMBOL
V
HYS_PG
V
GOH
I
GUP
I
GD
GATE_ Pulldown Current
I
GDS
SET_ to GATE_ Delay
FAULT,
PG/RST Output Low
Tracking Differential Voltage Stop
Ramp
Tracking Differential Fault Voltage
Tracking Differential Voltage
Hysteresis
Power-Low Threshold
Power-Low Hysteresis
OUT to GND Pulldown Impedance
MARGIN, TRK/SEQ, LTCH/RTR
Pullup Current
MARGIN, TRK/SEQ, LTCH/RTR
Input Voltage
MARGIN, TRK/SEQ, LTCH/RTR
Glitch Rejection
I
IN
V
IL
V
IH
2.0
100
V
TH_PL
V
TH_PLHYS
OUT_ falling
OUT_ rising
V
ABP
> 2.7V (Note 6)
7
125
t
D-GATE
V
OL
V
OUT_
rising
I
SOURCE
= 0.5µA
During power-up and power-down,
V
GATE_
= 1V
During power-up and power-down,
V
GATE_
= 5V
When disabled, V
GATE_
= 5V, V
IN_
≥
2.7V
When disabled, V
GATE_
= 5V, V
IN_
≥
4V
SET falling, 25mV overdrive
V
IN_
≥
2.7V, I
SINK
= 1mA, output asserted
V
IN_
≥
4.0V, I
SINK
= 4mA, output asserted
Differential between each of the OUT_ and
the ramp voltage during power-up and
power-down, Figure 10 (Note 5)
Differential between each of the OUT_ and
the ramp voltage, Figure 10 (Note 5)
75
125
IN_ +
4.2
2.5
2.5
CONDITIONS
MIN
TYP
0.5
IN_ +
5.0
4
4
9.5
20
6
0.3
0.4
180
IN_ +
5.8
MAX
UNITS
%
V
µA
µA
mA
µs
V
MAX6877/MAX6878/MAX6879
V
TRK
mV
V
TRK_F
200
250
20
142
10
100
10
310
mV
%
170
mV
mV
Ω
13
0.8
µA
V
ns
Note 1:
Specifications guaranteed for the stated global conditions. 100% production tested at T
A
= +25°C and T
A
= +85°C.
Specifications at T
A
= -40°C to +85°C are guaranteed by design. These devices meet the parameters specified when at
least one of V
CC
, IN1/IN2/IN3 is between 2.7V to 5.5V, while the remaining IN1/IN2/IN3 are between 0 and 5.5V.
Note 2:
A current I
D
= 2.5µA ±15% is generated internally and is used to set the DELAY and TIMEOUT periods and used as a refer-
ence for t
DELAY
and t
TIMEOUT
.
Note 3:
The total DELAY is t
DELAY
= 200ms + (500kΩ x C
DELAY
). Leave DELAY unconnected for 200µs delay. The total TIMEOUT is
t
TIMEOUT
= 200µs + (500kΩ x C
TIMEOUT
). Leave TIMEOUT unconnected for 200µs timeout.
Note 4:
A current I
S
= 25µA ±10% is generated internally and used as a reference for t
FAULT
, t
RETRY
, and slew rate.
Note 5:
During power-up, only the condition OUT_ < ramp - V
TRK
is checked in order to stop the ramp. However, both conditions
OUT_ < ramp - V
TRK_F
and OUT_ > ramp + V
TRK_F
cause a fault. During power-down, only the condition OUT > ramp +
V
TRK
is checked in order to stop the ramp. However, both conditions OUT_ < ramp - V
TRK_F
and OUT_ > ramp + V
TRK_F
cause a fault (see Figure 10). Therefore, if OUT1, OUT2, and OUT3 (during power-up tracking and power-down) differ by
more than 2 x V
TRK_F
, a fault condition is asserted.
Note 6:
A 100Ω pulldown to GND activated by a fault condition. See the
Internal Pulldown
section.
_______________________________________________________________________________________
3
Dual-/Triple-Voltage, Power-Supply
Trackers/Sequencers/Supervisors
MAX6877/MAX6878/MAX6879
EN/UV
V
EN_R
EN/UV
BUS VOLTAGE MONITORED THROUGH EN/UV INPUT
EN/UV
V
EN_F
IN1 = 2.5V
IN2 = 1.8V
IN_
IN3 = 0.7V
MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS
CAPACITOR-
ADJUSTED
SLEW RATE
OUT1 = 2.5V
OUT2 = 1.8V
OUT_
OUT3 = 0.7V
t
DELAY
PG/RST
t
TIMEOUT
Figure 1. Tracking Timing Diagram in Normal Mode
4
_______________________________________________________________________________________
Dual-/Triple-Voltage, Power-Supply
Trackers/Sequencers/Supervisors
MAX6877/MAX6878/MAX6879
EN/UV
V
EN_R
BUS VOLTAGE MONITORED THROUGH EN/UV INPUT
EN/UV
V
EN_F
IN1 = 2.5V
IN2 = 1.8V
IN_
IN3 = 0.7V
MONITORED THROUGH SET THRESHOLDS ON SET_ INPUTS
CAPACITOR-
ADJUSTED
SLEW RATE OUT1 = 2.5V
OUT2 = 1.8V
OUT_
OUT3 = 0.7V
IN1 GOES BELOW
SET1 THRESHOLD
t
DELAY
t
TIMEOUT
PG/RST
FAULT = HIGH
FORCED INTO QUICK SHUTDOWN AFTER NORMAL SHUTDOWN WHEN IN1 GOES BELOW ITS SET VOLTAGE
Figure 2. Tracking in Fast Shutdown Mode
_______________________________________________________________________________________
5
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