Rainbow Electronics MAX16066 - Manual (Page 51)

12-Channel/8-Channel, Flash-Configurable System
Managers with Nonvolatile Fault Registers
MAX16065/MAX16066
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required, t FAULT_SAVE . Use the following formula to cal-
culate the capacitor size:
C = (t
FAULT_SAVE x I CC(MAX) )/(V IN - V DIODE - V UVLO )
where the capacitance is in Farads and t FAULT_SAVE is in
seconds, I CC(MAX) is 14mA, V DIODE is the voltage drop
across the diode, and V UVLO is 2.7V. For example, with
a V IN of 14V, a diode drop of 0.7V, and a t FAULT_SAVE
of 153ms, the minimum required capacitance is 202FF.
Driving High-Side MOSFET Switches
Up to eight of the programmable outputs (EN_OUT1–
EN_OUT8) of the MAX16065/MAX16066 can be config-
ured as charge-pump outputs to drive the gates of series-
pass n-channel MOSFETS. When driving MOSFETs,
these outputs act as simple power switches to turn on
the voltage supply rails. Approximate the slew rate, SR,
using the following formula:
SR = I CP /(C GATE + C EXT )
where I CP is the 4FA (typ) charge-pump source current,
C GATE is the gate capacitance of the MOSFET, and C EXT
is the capacitance connected from the gate to ground.
If more than eight series-pass MOSFETs are required
for an application, additional series-pass p-channel
MOSFETS can be connected to outputs configured as
active-low open drain (Figure 18). Connect a pullup
resistor from the gate to the source of the MOSFET, and
ensure the absolute maximum ratings of the MAX16065/
MAX16066 are not exceeded.
Configuring the Device
An evaluation kit and a graphical user interface (GUI) is
available to create a custom configuration for the device.
Refer to the MAX16065/MAX16066 Evaluation Kit for
configuration.
Cascading Multiple MAX16065/MAX16066s
Multiple MAX16065/MAX16066s can be cascaded to
increase the number of rails controlled for sequencing
and monitoring. There are many ways to cascade the
devices depending on the desired behavior. In general,
there are several techniques:
U
Configure a GPIO_ on each device to be EXTFAULT
(open drain). Externally wire them together with a
single pullup resistor. Set register bits r72h[5] and
r6Dh[2] to ‘1’ so that all faults will propagate between
devices. If a critical fault occurs on one device,
EXTFAULT will assert, triggering the nonvolatile fault
logger in all cascaded devices and recording a snap-
shot of all system voltages.
U
Connect open-drain RESET outputs together to obtain
a master system reset signal.
U
Connect all EN inputs together for a master enable sig-
nal. Since the internal timings of each cascaded device
are not synchronized, EN_OUT_s placed in the same
Table 33. Maximum Write Time
Figure 17. Power Circuit for Shutdown During Fault Conditions
Figure 18. Connection for a p-Channel Series-Pass MOSFET
R6Dh[1:0]
VALUE
DESCRIPTION
MAXIMUM
WRITE TIME
(ms)
00
Save flags and ADC
readings
244
01 Save flags 77
10 Save ADC readings 153
11 Do not save anything —
MAX16065
MAX16066
V CC
C
V IN
GND
MAX16065
MAX16066
V OUT
R
MON_ EN_OUT_
V IN