MAX17020ETJ+ Maxim Integrated Products, MAX17020ETJ+ Datasheet - Page 23

• Manufacturer Part Number: MAX17020ETJ+
• Description: IC CTLR PWM DUAL STEP DN 32-TQFN
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r
• Type: Dual Quick-PWM Step-Down Controllerr

Specifications of MAX17020ETJ+

• Applications: Power Supplies
• Current - Supply: 1mA
• Voltage - Supply: 6 V ~ 24 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Output Voltage Range: 0.7 V to 5.5 V
• Input Voltage Range: 6 V to 24 V
• Input Current: 1 mA
• Power Dissipation: 2.76 W
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX17020 regulates OUT2 to the voltage set at
REFIN2, so the MAX17020 supports applications that
require dynamic output-voltage changes between two
set points by adjusting the REFIN2 voltage. For a step-
voltage change at REFIN2, the rate of change of the
output voltage is limited either by the internal slew-rate
circuit, by the REFIN2 slew rate, or by the component
selection—inductor current ramp, the total output
capacitance, the current limit, and the load during the
transition—whichever is the slowest. The total output
capacitance determines how much current is needed to
change the output voltage, while the inductor limits the
current ramp rate. Additional load current slows down
the output voltage change during a positive REFIN2
voltage change, and speeds up the output voltage
change during a negative REFIN2 voltage change.
Figure 5 is the dynamic REFIN transition.
When the MAX17020 automatically detects that the
internal target and REFIN2 are more than ±25mV (typ)
apart, the controller automatically blanks PGOOD2,
blanks the UVP protection, and sets the OVP threshold
to REF + 200mV. The blanking remains until 1) the inter-
nal target and REFIN2 are within ±20mV of each other
and 2) an edge is detected on the error amplifier signi-
fying that the output is in regulation. This prevents the
system or internal fault protection from shutting down
the controller during transitions.
Figure 5. Dynamic REFIN Transition
Dynamic Output Voltage—OUT2 Only
VOLTAGE
OUTPUT
PGOOD
REFIN
OVP
LX
______________________________________________________________________________________
BLANK HIGH-Z
Dual Quick-PWM Step-Down Controller
REF + 140mV
20mV
with Low-Power LDO, RTC Regulator
Automatic Fault Blanking
INTERNAL EA TARGET = ACTUAL V
INTERNAL TARGET AND REFIN2
±20mV WINDOW BETWEEN
EA TARGET + 140mV
The current-limit circuit employs a unique “valley” cur-
rent-sensing algorithm that senses the inductor current
through the low-side MOSFET—across LX to AGND. If
the current through the low-side MOSFET exceeds the
valley current-limit threshold, the PWM controller is not
allowed to initiate a new cycle. The actual peak current
is greater than the valley current-limit threshold by an
amount equal to the inductor ripple current. Therefore,
the exact current-limit characteristic and maximum load
capability are a function of the inductor value and bat-
tery voltage. When combined with the undervoltage
protection circuit, this current-limit method is effective in
almost every circumstance.
In forced-PWM mode, the MAX17020 also implements
a negative current limit to prevent excessive reverse
inductor currents when V
negative current-limit threshold is set to approximately
120% of the positive current limit.
When V
old, the MAX17020 clears the fault latches, forces the
low-side MOSFET to turn on (DL high), and resets the
soft-start circuit, preparing the controller for power-up.
However, the V
inhibits switching until V
V
enabled (ON_ pulled high), the controller activates the
enabled PWM controllers and initializes soft-start.
CC
OUT
rises above 4.2V and the controller has been
CC
rises above the power-on reset (POR) thresh-
BLANK HIGH-Z
CC
Valley Current-Limit Protection
20mV
undervoltage lockout (UVLO) circuitry
CC
OUT
EA TARGET + 140mV
reaches 4.2V (typ). When
is sinking current. The
DYNAMIC REFIN WINDOW
POR, UVLO
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