MAX15034BEVKIT+ Maxim Integrated Products, MAX15034BEVKIT+ Datasheet - Page 13

• Manufacturer Part Number: MAX15034BEVKIT+
• Description: KIT EVALUATION FOR MAX15034
• Manufacturer: Maxim Integrated Products

Specifications of MAX15034BEVKIT+

• Main Purpose: DC/DC, Step Down
• Voltage - Input: 5 ~ 28V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: MAX15034
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Output: -
• Power - Output: -
• Frequency - Switching: -
• Outputs And Type: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The MAX15034 includes overload fault protection circuitry
that prevents damage to the power MOSFETs. The fault
protection consists of two digital fault integration blocks
that enable hiccuping under overcurrent conditions. This
circuit works as follows: for every clock cycle the current-
limit threshold is exceeded, the fault integration counter
increments by one count. Thus, if the current-limit condi-
tion persists, the counter reaches its shutdown threshold
in 32,768 counts and shuts down the external MOSFETs.
When the MAX15034 shuts down due to a fault, the
counter begins to count down (since the current-limit con-
dition has ended), once every 16 clock cycles. Thus, the
device counts down for 524,288 clock cycles. At this
point, switching resumes. This produces an effective duty
cycle of 6.25% power-up and 93.75% power-down under
fault conditions. With a switching frequency set to
250kHz, power-up and power-down times are approxi-
mately 131ms and 2.09s, respectively.
The MAX15034 uses an average current-mode control
topology to regulate the output voltage. The control
loop consists of an inner current loop and an outer volt-
age loop. The inner current loop controls the output
Figure 2. Current and Voltage Loops
Configurable, Single-/Dual-Output, Synchronous
Buck Controller for High-Current Applications
V
VEA1
REF
R
= 0.61V
F
CSN1
______________________________________________________________________________________
CA 1
Hiccup Fault Protection
CSP1
CEA1
2V
P-P
CLP1
Control Loop
CPWM1
R
CF
C
C
CFF
CF
DRIVE
current, while the outer voltage loop controls the output
voltage. The inner current loop absorbs the inductor
pole, reducing the order of the outer voltage loop to
that of a single-pole system. Figure 2 is the block dia-
gram of OUT1’s control loop.
The current loop consists of a current-sense resistor,
R
error amplifier (CEA1), an oscillator providing the carri-
er ramp, and a PWM comparator (CPWM1). The
precision current-sense amplifier (CA1) amplifies the
sense voltage across R
inverting input to CEA1 senses the output of CA1. The
output of CEA1 is the difference between the voltage-
error amplifier output (EAOUT1) and the gained-up volt-
age from CA1. The RC compensation network
connected to CLP1 provides external frequency com-
pensation for the respective CEA1 (see the
Compensation section). The start of every clock cycle
enables the high-side driver and initiates a PWM on-
cycle. Comparator CPWM1 compares the output volt-
age from CEA1 against a 0 to 2V ramp from the
oscillator. The PWM on-cycle terminates when the ramp
voltage exceeds the error voltage from the current-error
amplifier (CEA1).
SENSE
V
IN
, a current-sense amplifier (CA1), a current-
I
L
R
SENSE
SENSE
C
OUT
by a factor of 36. The
V
LOAD
OUT1
R1
R2
13