MAX5037 MAXIM [Maxim Integrated Products], MAX5037 Datasheet - Page 16

• Manufacturer Part Number: MAX5037
• Description: VRM 9.0, Dual-Phase, Parallelable, Average Current-Mode Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

The differential current-sense amplifier (CA_) provides a
DC gain of 18. The maximum input offset voltage of the
current-sense amplifier is 1mV and the common-mode
voltage range is -0.3V to +3.6V. The current-sense ampli-
fier senses the voltage across a current-sense resistor.
The peak-current comparator provides a path for fast
cycle-by-cycle current limit during extreme fault condi-
tions such as an output inductor malfunction (Figure 4).
Note that the average current-limit threshold of 48mV
still limits the output current during short-circuit condi-
tions. So to prevent inductor saturation, select an out-
put inductor with a saturation current specification
greater than the average current limit. Proper inductor
selection ensures that only extreme conditions trip the
peak-current comparator, such as a cracked output
inductor. The 112mV voltage threshold for triggering
the peak-current limit is twice the full-scale average
current-limit voltage threshold. The peak-current com-
parator has a delay of only 260ns.
Each phase of the MAX5037 has a dedicated transcon-
ductance current-error amplifier (CEA_) with a typical
g
capability. The CEA_ outputs, CLP1 and CLP2, serve
as the inverting input to the PWM comparator. CLP1
and CLP2 are externally accessible to provide frequen-
cy compensation for the inner current loops (Figure 3).
Compensate CEA_ such that the inductor current down
VRM 9.0, Dual-Phase, Parallelable,
Average Current-Mode Controller
Figure 4. Phase Circuit (Phase 1/Phase 2)
16
m
of 550µS and 320µA output sink and source current
______________________________________________________________________________________
CLP_
CSP_
CSN_
GM
RAMP
CLK
SHDN
IN
2 x f
S
(V/s)
A
112mV
V
Peak-Current Comparator
= 18
Current-Sense Amplifier
Current-Error Amplifier
PEAK CURRENT
COMPARATOR
G
500µS
m
=
PWM
COMPARATOR
slope, which becomes the up slope to the inverting
input of the PWM comparator, is less than the slope of
the internally generated voltage ramp (see the
Compensation section).
The PWM comparator (CPWM) sets the duty cycle for
each cycle by comparing the current-error amplifier
output to a 2V
an R-S flip-flop resets and the high-side driver (DH_)
turns on. The comparator sets the flip-flop as soon as
the ramp voltage exceeds the CLP_ voltage, thus termi-
nating the ON cycle (Figure 4).
The unity-gain differential amplifier (DIFF AMP) facili-
tates the output voltage remote sensing at the load
(Figure 3). It provides true differential output voltage
sensing while rejecting the common-mode voltage
errors due to high-current ground paths. Sensing the
output voltage directly at the load provides accurate
load voltage sensing in high-current environments. The
VEA provides the difference between the differential
amplifier output (DIFF) and the desired VID pro-
grammed output voltage. The differential amplifier has
a unity-gain bandwidth of 3MHz. The difference
between SENSE+ and SENSE- regulates to the pro-
grammed VID output voltage.
Connect SENSE+ to an external resistor-divider network
at the output voltage to use the MAX5037 for output
voltages higher than those allowed by the VID codes.
S
R
P-P
Q
Q
ramp. At the start of each clock cycle,
PWM Comparator and R-S Flip-Flop
DRV_V
CC
Differential Amplifier
PGND
BST_
DH_
DL_
LX_