MAX1980ETP+ Maxim Integrated Products, MAX1980ETP+ Datasheet - Page 27

• Manufacturer Part Number: MAX1980ETP+
• Description: IC CNTRLR QUICK-PWM 20-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1980ETP+

• Pwm Type: Controller
• Number Of Outputs: 1
• Frequency - Max: 550kHz
• Duty Cycle: 50%
• Voltage - Supply: 4 V ~ 28 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 85°C
• Package / Case: 20-TQFN Exposed Pad
• Frequency-max: 550kHz
• Input Voltage: 4 V to 28 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX1980 can be used with a direct battery con-
nection (one stage) or can obtain power from a regulat-
ed 5V supply (two-stage). Each approach has
advantages, and careful consideration should go into
the selection of the final design.
The one-stage approach offers smaller total inductor
size and fewer capacitors overall due to the reduced
demands on the 5V supply. Due to the high input volt-
age, the one-stage approach requires lower DC input
currents, reducing input connection/bus requirements
and power dissipation due to input resistance. The
transient response of the single stage is better due to
the ability to ramp the inductor current faster. The total
efficiency of a single stage is better than the two-stage
approach.
The two-stage approach allows flexible placement due
to smaller circuit size and reduced local power dissipa-
tion. The power supply can be placed closer to the
CPU for better regulation and lower I
board traces. Although the two-stage design has slow-
er transient response than the single stage, this can be
offset by the use of a voltage-positioned converter.
Ceramic capacitors have advantages and disadvan-
tages. They have ultra-low ESR and are noncom-
bustible, relatively small, and nonpolarized. However,
they are also expensive and brittle, and their ultra-low
ESR characteristic can result in excessively high ESR
zero frequencies. In addition, their relatively low capac-
itance value can cause output overshoot when step-
ping from full-load to no-load conditions, unless a small
inductor value is used (high switching frequency), or
there are some bulk tantalum or electrolytic capacitors
in parallel to absorb the stored inductor energy. In
some cases, there may be no room for electrolytics,
creating a need for a DC-DC design that uses nothing
but ceramics.
The MAX1980 can take full advantage of the small size
and low ESR of ceramic output capacitors in a voltage-
positioned circuit. The addition of the positioning resis-
tor increases the ripple at FB, lowering the effective
ESR zero frequency of the ceramic output capacitor.
Output overshoot (V
output capacitance requirement (see the Output
Capacitor Selection section). Often the switching fre-
quency is increased to 550kHz, and the inductor value
is reduced to minimize the energy transferred from
inductor to capacitor during load-step recovery. The
Driver Disable for Multiphase DC-DC Converter
Ceramic Output Capacitor Applications
Two-Stage (5V Input) Applications
One-Stage (Battery Input) vs.
______________________________________________________________________________________
SOAR
) determines the minimum
Quick-PWM Slave Controller with
2
R losses from PC
efficiency penalty for operating at 550kHz is about 3%
when compared to the 300kHz circuit, primarily due to
the high-side MOSFET switching losses.
Careful PC board layout is critical to achieve low
switching losses and clean, stable operation. The
switching power stage requires particular attention
(Figure 10). If possible, mount all of the power compo-
nents on the top side of the board with their ground ter-
minals flush against one another. Follow these
guidelines for good PC board layout:
1) Keep the high-current paths short, especially at the
2) Connect all analog grounds to a separate solid
3) The master controller also should have a separate
4) Keep the power traces and load connections short.
5) Keep the high-current gate-driver traces (DL, DH,
6) CS+, CS-, CM+, and CM- connections for current
7) When trade-offs in trace lengths must be made, it’s
ground terminals. This is essential for stable, jitter-
free operation
copper plane, which connects to the GND pin of
the MAX1980. This includes the V
itor, COMP components, and the resistive-divider
connected to ILIM.
analog ground. Return the appropriate noise sensi-
tive components to this plane. Since the reference
in the master is sometimes connected to the slave,
it may be necessary to couple the analog ground in
the master to the analog ground in the slave to pre-
vent ground offsets. A low value (≤10Ω) resistor is
sufficient to link the two grounds.
This is essential for high efficiency. The use of thick
copper PC boards (2oz vs. 1oz) can enhance full-
load efficiency by 1% or more. Correctly routing PC
board traces is a difficult task that must be
approached in terms of fractions of centimeters,
where a single mΩ of excess trace resistance caus-
es a measurable efficiency penalty.
LX, and BST) short and wide to minimize trace
resistance and inductance. This is essential for
high-power MOSFETs that require low-impedance
gate drivers to avoid shoot-through currents.
limiting and balancing must be made using Kelvin
sense connections to guarantee the current-sense
accuracy.
preferable to allow the inductor charging path to be
made longer than the discharge path. For example,
it’s 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-
PC Board Layout Guidelines
CC
bypass capac-
27