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| MAX15003 Datasheet, PDF (17/32 Pages) Maxim Integrated Products – Triple-Output Buck Controller with Tracking/Sequencing | |||
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Triple-Output Buck Controller with
Tracking/Sequencing
RATIOMETRIC TRACKING
VIN
EN1
COINCIDENT TRACKING
VIN
EN1
PGOOD SEQUENCING
VIN
EN1
EN/TRACK2
EN/TRACK3
SEL
VOUT1
REG
RA
EN/TRACK2
RB
RC
PGOOD1
EN/TRACK2
REG
REG
EN/TRACK3
VOUT2
FB2
VOUT3
RA
FB3
RD
RC
PGOOD2
EN/TRACK3
RB
RD
SEL
SEL
REG
Figure 2. Ratiometric Tracking, Coincident Tracking, PGOOD Sequencing Configurations
Error Amplifier
The output of the internal error transconductance
amplifier (COMP_) is provided for frequency compen-
sation (see the Compensation Design Guidelines sec-
tion). The inverting input is FB_ and the output COMP_.
The error transamplifier has an 80dB open-loop gain
and a 10MHz GBW product.
Output Short-Circuit Protection
(Hiccup Mode)
The current-limit circuit employs a valley current-limiting
algorithm that either uses a shunt or the synchronous
MOSFETâs on-resistance as the current-sensing ele-
ment. Once the high-side MOSFET turns off, the volt-
age across the current-sensing element is monitored. If
this voltage does not exceed the current-limit threshold,
the high-side MOSFET turns on normally at the start of
the next cycle. If the voltage exceeds the current-limit
threshold just before the beginning of a new PWM
cycle, the controller skips that cycle. During severe
overload or short-circuit conditions, the switching fre-
quency of the device appears to decrease because the
on-time of the low-side MOSFET extends beyond a
clock cycle.
If the current-limit threshold is exceeded for more than
eight cumulative clock cycles (NCL), the device shuts
down (both DH and DL are pulled low) for 4096 clock
cycles (hiccup timeout) and then restarts with a soft-
start sequence. If three consecutive cycles pass with-
out a current-limit event, the count of NCL is cleared
(see Figure 3). Hiccup mode protects against a contin-
uous output short circuit.
______________________________________________________________________________________ 17
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