MAX888ECJ Maxim, MAX888ECJ Datasheet - Page 17

• Manufacturer Part Number: MAX888ECJ
• Description: Wireless and Satellite Handset Power-Management ICs
• Manufacturer: Maxim

faster, such as the MUR series, are acceptable. Ensure
that the diode’s peak current rating exceeds the peak
current (1A), and that its breakdown voltage exceeds
V
due to their low forward voltage, especially in low-volt-
age applications.
Choose filter capacitors to service input and output
peak currents with acceptable voltage ripple. The
capacitor’s equivalent series resistance (ESR) is a
major contributor to ripple; therefore, low-ESR capaci-
tors are recommended for OUT1–OUT5. A tantalum
capacitor is recommended for OUT0 (refer to Figures
2a and 2b, and Table 6).
The input filter capacitor reduces peak currents drawn
from the power source, and reduces noise and voltage
ripple on the input, which are caused by the circuit’s
switching action. Since the current from the battery is
interrupted each time the PMOS switch opens, pay spe-
cial attention to the ripple current rating of the input filter
capacitor and use a low-ESR capacitor. Choose input
capacitors with working voltage ratings higher than the
maximum input voltage. Input capacitors prevent spikes
and ringing on the power source from obscuring the
current-feedback signal and causing jitter.
Bypass REF with 0.22µF to GND. The capacitor should
be placed within 0.2 inches of the IC, next to REF, with
a direct trace to GND.
Table 6. OUT0 and OUT4 Regulator
Component Recommendations
BATT
(kHz)
f
925
670
535
375
OSC
. Schottky diodes are preferred for heavy loads
(µF)
C11
10
15
22
33
______________________________________________________________________________________
(µH)
L1
10
15
22
33
Capacitor Selection
(µF)
0.22
0.33
0.47
C6
1
Wireless and Satellite Handset
(µF)
C12
10
15
22
33
Power-Management ICs
Table 7. Component Suppliers
High-frequency switching regulators are sensitive to PC
board layout. Poor layout introduces switching noise
into the current and voltage-feedback signals, resulting
in jitter, instability, or degraded performance. Place the
anode of the Schottky diode and the ground pins of the
input and output capacitors close together, and route
them to a common “star-ground” point. Place compo-
nents and route ground paths so as to prevent high
currents from causing large voltage gradients between
the ground pin of the output filter capacitor, the con-
troller IC, and the reference bypass capacitor. Keep
the extra copper on the component and solder sides of
the PC board rather than etching it away, and connect
it to ground for use as a pseudo-ground plane. Refer to
the MAX886/MAX888 evaluation kit for a two-layer PC
board layout example.
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Layout Considerations
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