MAX5096/MAX5097
Output Voltage Tracking/Sequencing
The output voltages of multiple MAX5096/MAX5097
converters can be made to track by using the SS pin
during turn-on and turn-off (see Figure 3). SS is pulled
up using a 5µA current source and connecting SS of
multiple MAX5096/MAX5097s, raising the references
with the same slope. Tracking the converters reduces
the differential voltages between the core and I/O volt-
ages during turn-on, turn-off, and brownout. If any one
converter output drops due to shutdown or an overload
fault situation, the SS drops, pulling down all the con-
verters simultaneously. The rate of fall of output volt-
ages, however, depends on the output capacitance
and load of the individual converter.
Multiple voltage sequencing can be done by daisy-
chaining several MAX5096/MAX5097s. The RESET of
the first converter can be connected to EN of the sec-
ond converter. This allows the first converter to come
up first every time the system is powered up.
Power-On Reset Output (
RESET
)
A supervisor circuit is integrated in the MAX5096/
MAX5097. RESET is an open-drain output. RESET pulls
low as soon as V
OUT
drops below 90% of its nominal
regulation voltage. Once the output voltage rises above
92% of the set output voltage, the RESET output enters
a high-impedance state after the active timeout period
(t
RP
). The active timeout period is externally program-
mable using a single capacitor from CT to ground. Use
the following equation to calculate the required timeout
period for the power-on reset:
where V
CT-TH
is 1.237V, I
CH
is 1µA, t
RP
is in seconds,
and C
CT
is in Farads.
To obtain a logic-voltage output, connect a pullup
resistor from RESET to a logic-supply voltage. The
internal open-drain MOSFET can sink 1mA while provid-
ing a TTL logic-low signal. If unused, ground RESET or
leave it unconnected.
The power-on reset behavior is the same in both the
LDO and Buck Modes of operation.
Oscillator/Synchronization Input (SYNC)
The MAX5096/MAX5097 internal oscillator generates a
factory-preset frequency of either 135kHz (MAX5096)
or 330kHz (MAX5097). The 135kHz version keeps the
maximum fundamental frequency below 150kHz, which
keeps the third harmonic below 450kHz and under the
(8 Seiten)
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