MAX17020ETJ+T Maxim Integrated Products, MAX17020ETJ+T Datasheet - Page 31

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

Specifications of MAX17020ETJ+T

• 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
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Careful PCB layout is critical to achieving low switching
losses and clean, stable operation. The switching
power stage requires particular attention. If possible,
mount all the power components on the top side of the
board, with their ground terminals flush against one
another. Follow these guidelines for good PCB layout:
•
•
•
•
•
A sample layout is available in the MAX17020 evalua-
tion kit data sheet.
Table 5. MAX17020 vs. MAX8778 Design Differences
RTC power-up required for controller operation.
Keep the high-current paths short, especially at the
ground terminals. This practice is essential for sta-
ble, jitter-free operation.
Keep the power traces and load connections short.
This practice is essential for high efficiency. Using
thick copper PCBs (2oz vs. 1oz) can enhance full-
load efficiency by 1% or more. Correctly routing
PCB traces is a difficult task that must be
approached in terms of fractions of centimeters,
where a single milliohm of excess trace resistance
causes a measurable efficiency penalty.
Minimize current-sensing errors by connecting LX_
directly to the drain of the low-side MOSFET.
When trade-offs in trace lengths must be made, it is
preferable to allow the inductor charging path to be
made longer than the discharge path. For example,
it is better to allow some extra distance between the
input capacitors and the high-side MOSFET than to
allow distance between the inductor and the low-
side MOSFET or between the inductor and the out-
put filter capacitor.
Route high-speed switching nodes (BST_, LX_,
DH_, and DL_) away from sensitive analog areas
(REF, FB_, and OUT_).
______________________________________________________________________________________
Dual Quick-PWM Step-Down Controller
MAX17020
PCB Layout Guidelines
with Low-Power LDO, RTC Regulator
LDO and switching regulators independent of RTC operation.
1) Place the power components first, with ground ter-
2) Mount the controller IC adjacent to the low-side
3) Group the gate-drive components (BST_ capacitor,
4) Make the DC-DC controller ground connections as
5) Connect the output power planes directly to the out-
minals adjacent (N
anode). If possible, make all these connections on
the top layer with wide, copper-filled areas.
MOSFET, preferably on the back side opposite N
and N
drive lines short and wide. The DL_ and DH_ gate
traces must be short and wide (50 mils to 100 mils
wide if the MOSFET is 1in from the controller IC) to
keep the driver impedance low and for proper
adaptive dead-time sensing.
V
shown in Figures 1 and 6. This diagram can be
viewed as having two separate ground planes:
power ground, where all the high-power compo-
nents go; and an analog ground plane for sensitive
analog components. The analog ground plane and
power ground plane must meet only at a single
point directly at the IC.
put filter capacitor positive and negative terminals
with multiple vias. Place the entire DC-DC converter
circuit as close to the load as is practical.
DD
bypass capacitor) together near the controller IC.
H_
to keep LX_, GND, DH_, and the DL_ gate-
MAX8778
L_
source, C
IN
Layout Procedure
, C
OUT_
, and D
31
L_
L_