MAX5037 MAXIM [Maxim Integrated Products], MAX5037 Datasheet - Page 15

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

The current loop consists of a current-sense resistor,
R
current sensing), a current-sense amplifier (CA_), a
current-error amplifier (CEA_), an oscillator providing
the carrier ramp, and a PWM comparator (CPWM_).
The precision CA_ amplifies the sense voltage across
R
senses the output of the CA_. The output of the CEA_ is
the difference between the voltage-error amplifier out-
put (EAOUT) and the gained-up voltage from the CA_.
The RC compensation network connected to CLP1 and
CLP2 provides external frequency compensation for
the respective CEA_. The start of every clock cycle
enables the high-side drivers and initiates a PWM ON
cycle. Comparator CPWM_ compares the output volt-
age from the CEA_ with a 0 to 2V ramp from the oscilla-
tor. The PWM ON cycle terminates when the ramp
voltage exceeds the error voltage.
Figure 3. MAX5037 Control Loop
S
S
(an RC lowpass filter in the case of lossless inductor
by a factor of 18. The inverting input to the CEA_
SENSE+
SENSE-
*R
(R
F
F
= R8, R
AND R
______________________________________________________________________________________
DIFF
AMP
IN
IN
ARE EXTERNAL TO MAX5037
= R7, FIGURES 1 AND 2)
MAX5037
AVP
DAC
R
IN
*
VRM 9.0, Dual-Phase, Parallelable,
VEA
R
F
Average Current-Mode Controller
*
CA1
CA2
CEA1
CEA2
CPWM1
CPWM2
R
R
CF
CF
The outer voltage control loop consists of the differen-
tial amplifier (DIFF AMP), adaptive voltage-positioning
(AVP) block, digital-to-analog converter (DAC), and
voltage-error amplifier (VEA). The unity-gain differential
amplifier provides true differential remote sensing of the
output voltage. The differential amplifier output and the
AVP connect to the inverting input (EAN) of the VEA.
The noninverting input of VEA is internally connected to
the DAC output. The VEA controls the two inner current
loops (Figure 3). Use a resistive feedback network to
set the gain of the VEA as required by the adaptive
voltage-positioning circuit.
C
C
CCF
CFF
C
C
CF
CF
DRIVE 1
DRIVE 2
V
V
IN
IN
I
I
PHASE1
PHASE2
R
R
S
S
C
OUT
V
OUT
LOAD
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