MAX6877ETG+ Maxim Integrated Products, MAX6877ETG+ Datasheet - Page 18

• Manufacturer Part Number: MAX6877ETG+
• Description: IC SEQUENCE/SUPERVISOR 24TQFN
• Manufacturer: Maxim Integrated Products
• Type: Sequencerr

Specifications of MAX6877ETG+

• Number Of Voltages Monitored: 3
• Output: Open Drain or Open Collector
• Reset: Active Low
• Reset Timeout: Adjustable/Selectable
• Voltage - Threshold: Adjustable/Selectable
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-TQFN Exposed Pad
• Monitored Voltage: - 0.3 V to + 6 V
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 2.7 V
• Supply Current (typ): 1100 uA
• Maximum Power Dissipation: 1667 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

voltages below the adjusted thresholds to avoid signal-
ing an error. The state of PG/RST and FAULT outputs
does not change while MARGIN is low. PG/RST,
FAULT, and all monitoring functions are disabled while
MARGIN is low. MARGIN makes it possible to vary the
supplies without a need to adjust the thresholds to pre-
vent tracker/sequencer alerts or faults. Drive MARGIN
high or leave it unconnected for normal operating
mode.
The reference ramp voltage slew rate during any con-
trolled power-up/down phase can be programmed in
the 90V/s to 950V/s range by connecting a capacitor
(C
mula to calculate the typical slew rate:
where slew rate is in V/s and C
The capacitor at C
period (t
(t
For example, if C
350ms, t
example, if C
t
C
large enough to make the parasitic capacitance negli-
gible. C
C
Table 1. C
Dual-/Triple-Voltage, Power-Supply
Trackers/Sequencers/Supervisors
Figure 9. Setting the Undervoltage (UVLO) Thresholds
18
FAULT
RETRY
SLEW
SLEW
SLEW
______________________________________________________________________________________
= 219ms, slew rate = 93.5V/s.
) (see Table 1).
< 1nF.
) from SLEW to ground. Use the following for-
is the capacitor on the SLEW pad, and must be
TIME PERIOD
V
SLEW
FAULT
IN_
FAULT
Slew Rate
Slew Rate = (9.35 x 10
t
t
RETRY
FAULT
SLEW
R2
R1
SLEW
should be in the range of 100pF <
= 21.91ms, slew rate = 935V/s. For
) and FAULT retry timeout period
SLEW
Timing Formulas
SLEW
= 1nF, we have t
Slew-Rate Control Input (SLEW)
IN_
SET_
= 100pF, we have t
also sets the FAULT timeout
MAX6877
MAX6878
MAX6879
SLEW
(9.35 x 10
3.506 x 10
2.191 x 10
-8
)/ C
is in farads.
FORMULAS
SLEW
RETRY
-8
9
8
) / C
x C
x C
SLEW
SLEW
RETRY
SLEW
= 3.5s,
=
The capacitor connected at SLEW controls the OUT_S
slew rate, thus controlling the inrush current required to
charge the load capacitor at the outputs (OUT_). Using
the programmed slew rate, limit the inrush current by
using the following formula:
where I
is in V/s.
To adjust the desired delay period (t
tracking/sequencing is enabled, connect a capacitor
(C
The selected delay time is also enforced when EN/UV
rises from low to high when all the input voltages
(IN1/IN2/IN3) are present. Use the following formula to
calculate the delay time:
where t
DELAY unconnected for the default 200µs delay.
These devices feature a PG/RST timeout period.
Connect a capacitor (C
ground to program the PG/RST timeout period. After all
OUT_ outputs exceed their IN_ referenced thresholds
(V
period, t
where t
Leave TIMEOUT unconnected for the default 200µs
timeout delay.
Drive logic EN/UV input above V
tracking/sequencing during the power-up operation.
Drive logic EN/UV below V
power-down operation. Connect EN/UV to an external
resistor-divider network to set the external undervoltage
lockout threshold.
The MAX6877 monitors three and MAX6878/MAX6879
monitor two OUT_ outputs to control the tracking/
sequencing performance. After the internal supply
(ABP) exceeds the minimum voltage (2.7V) require-
ments, EN/UV > V
than their adjusted SET_ thresholds, OUT1/OUT2/OUT3
begin to track or sequence.
TH_PG
DELAY
INRUSH
t
DELAY
TIMEOUT
TIMEOUT
) between DELAY to ground (see Figures 1 to 8).
), PG/RST remains low for the selected timeout
TIMEOUT
t
DELAY
is in µs and C
is in amperes, C
= 200µs + (500kΩ x C
= 200µs + (500kΩ x C
I
(see Figure 3):
INRUSH
is in µs and C
EN_R
Timeout Period Input (TIMEOUT)
, and IN1/IN2/IN3 are all greater
= C
TIMEOUT
Logic-Enable Input (EN/
Delay Time Input (DELAY)
OUT
DELAY
EN_F
Limiting Inrush Current
OUT
EN_R
TIMEOUT
x SR
) from TIMEOUT to
to initiate tracking
is in farads, and SR
OUT1/OUT2/OUT3
is in farads. Leave
to initiate voltage
DELAY
TIMEOUT
DELAY
is in farads.
)
) before
)
UV )