MAX8559 Maxim, MAX8559 Datasheet - Page 8

• Manufacturer Part Number: MAX8559
• Description: Dual / 300mA / Low-Noise Linear Regulator with Independent Shutdown in UCSP or TDFN
• Manufacturer: Maxim

The MAX8559 load-transient response graphs (see the
Typical Operating Characteristics) show two compo-
nents of the output response: a DC shift in the output
voltage due to the different load currents and the tran-
sient response. Typical overshoot for step changes in
the load current from 10µA to 100mA is 15mV. Increase
the output capacitor’s value and decrease its ESR to
attenuate transient spikes.
A regulator’s minimum input-output voltage differential
(or dropout voltage) determines the lowest usable sup-
ply voltage. In battery-powered systems, this determines
the useful end-of-life battery voltage. Because the
MAX8559 uses an internal P-channel MOSFET pass
transistor, its dropout voltage is a function of the drain-
to-source on-resistance (R
current (see the Typical Operating Characteristics).
The maximum output power of the MAX8559 is limited
by the maximum power dissipation of the package. By
calculating the power dissipation of the package as a
function of the input voltage, output voltages, and out-
put currents, the maximum input voltage can be
obtained. The maximum power dissipation should not
exceed the package’s maximum power rating.
Dual, 300mA, Low-Noise Linear Regulator
with Independent Shutdown in UCSP or TDFN
8
_______________________________________________________________________________________
Calculating the Maximum Output Power
P = (V
+ (
Load-Transient Considerations
VIN(MAX)
IN(MAX)
DS(ON)
- V
- V
OUTB
OUTA
) multiplied by the load
) x I
) x I
Dropout Voltage
OUTB
OUTA
in UCSP
where:
V
P
(379mW for the UCSP and 1951mW for the TDFN)
V
V
I
I
P should be less than P
consider the TDFN.
Due to the low output noise and tight output voltage
accuracy required by most applications, careful PC
board layout is required. An evaluation kit
(MAX8559EVKIT) is available to speed design.
Follow these guidelines for good PC board layout:
• Keep the input and output paths short and wide if
• Use thick copper PC boards (2oz vs. 1oz) to
• Place output, input, and bypass capacitors as close
• Ensure traces to BP and the BP capacitor are away
OUTA
OUTB
IN(MAX)
MAX
OUTA
OUTB
possible, especially at the ground terminals.
enhance thermal capabilities.
as possible to the IC.
from noisy sources to ensure low output voltage noise.
= maximum power dissipation of the package
= maximum output current of OUTA
= maximum output current of OUTB
= output voltage of OUTA
= output voltage of OUTB
= maximum input voltage
MAX
. If P is greater than P
Layout Guidelines
MAX
,