ltc3528b-2 Linear Technology Corporation, ltc3528b-2 Datasheet - Page 10

• Manufacturer Part Number: ltc3528b-2
• Description: 1a, 2mhz Synchronous Step-up Dc/dc Converter In 2mm ? 3mm Dfn
• Manufacturer: Linear Technology Corporation

LTC3528B-2
V
The LTC3528B-2 maintains voltage regulation even when
the input voltage is above the desired output voltage. Note
that the effi ciency is much lower in this mode, and the
maximum output current capability will be less. Refer to
the Typical Performance Characteristics.
SHORT-CIRCUIT PROTECTION
The LTC3528B-2 output disconnect feature allows an output
short circuit while maintaining a maximum internally set
current limit. To reduce power dissipation under short-
circuit conditions, the peak switch current limit is reduced
to 750mA (typical).
SCHOTTKY DIODE
Although not required, adding a Schottky diode from
SW to V
that this defeats the output disconnect and short-circuit
protection features.
PCB LAYOUT GUIDELINES
The high speed operation of the LTC3528B-2 demands
careful attention to board layout. A careless layout will
not produce the advertised performance. Figure 1 shows
the recommended component placement. A large ground
copper area with the package backside metal pad properly
APPLICATIONS INFORMATION
10
IN
> V
OUT
OUT
OPERATION
will improve effi ciency by about 2%. Note
Figure 1. Recommended Component Placement for Single Layer Board
PGOOD
SHDN
V
C
OUT
OUT
FB
1
2
3
4
LTC3528B-2
V
IN
+
soldered will help to lower the chip temperature. A multi-
layer board with a separate ground plane is ideal, but not
absolutely necessary.
COMPONENT SELECTION
Inductor Selection
The LTC3528B-2 can utilize small surface mount chip
inductors due to their fast 2MHz switching frequency.
Inductor values between 1.5μH and 3.3μH are suitable for
most applications. Larger values of inductance will allow
slightly greater output current capability by reducing the
inductor ripple current. Increasing the inductance above
10μH will increase size while providing little improvement
in output current capability.
The minimum inductance value is given by:
where:
Ripple = Allowable inductor current ripple (amps peak-
peak)
V
V
C
L >
8
7
6
5
IN
IN(MIN)
OUT(MAX)
V
SGND
PGND
SW
MULTIPLE VIAS
TO GROUND PLANE
IN
V
IN(MIN)
= Minimum input voltage
2 • Ripple • V
= Maximum output voltage
35282 F01
• V
(
OUT(MAX)
OUT(MAX)
– V
IN(MIN)
)
µH
3528b2f