1
DATASHEET
High Efficiency Buck-Boost Regulator with 4.2A Switches
ISL91108
The ISL91108 is a highly-integrated buck-boost switching
regulator that accepts input voltages either above or below the
regulated output voltage. Unlike other buck-boost regulators,
this regulator automatically transitions between operating
modes without significant output disturbance.
This device is capable of delivering up to 2.7A of burst current
(PVIN = 3V, V
OUT
= 3.3V), and provides excellent efficiency due
to its fully synchronous 4-switch architecture. No load
quiescent current of only 27.5µA also optimizes efficiency
under light-load conditions. Forced PWM and/or
synchronization to an external clock may also be selected for
noise sensitive applications.
The ISL91108 is designed for standalone applications and
supports a 3.3V fixed output voltage or variable output
voltages with an external resistor divider. Output voltages as
low as 1V or as high as 5.2V are supported using an external
resistor divider.
The ISL91108 requires only a single inductor and very few
external components. Power supply solution size is minimized
by a 2.34mmx1.72mm WLCSP and a 2.6MHz switching
frequency, which further reduces the size of external
components.
Related Literature
• AN1903 “ISL91108IIA-EVZ/ISL91108IIN-EVZ Evaluation
Board User Guide”
Features
• Accepts input voltages above or below regulated output
voltage
• Automatic and seamless transitions between buck and
boost modes
• Input voltage range: 1.8V to 5.5V
• Output current: up to 1.6A DC (PVIN = 2.8V, V
OUT
= 3.3V)
• Burst current: up to 2.7A (PVIN = 3V, V
OUT
= 3.3V, t
ON
<600µs, t = 4.6ms)
• High efficiency: up to 95%
• 27.5µA quiescent current maximizes light load efficiency
• 2.6MHz switching frequency minimizes external component
size
• Selectable forced PWM mode and external synchronization
• Fully protected for short-circuit, over-temperature, and
undervoltage
• Small 2.34mm x 1.72mm WLCSP
Applications
• Smartphones and tablets
• Wireless communication devices
• 2G/3G/4G power amplifiers
FIGURE 1. TYPICAL FIXED OUTPUT APPLICATION FIGURE 2. ISL91108IINZ EFFICIENCY vs OUTPUT CURRENT
VOUT
FB
C2
2x22µF
PVIN
V
IN
=
1.8V TO 5.5V
VIN
MODE
EN
C
1
2x10µF
ISL91108IINZ
GND
PGND
LX1
LX2
L1
1µH
V
OUT
= 3.3V
EFFICIENCY (%)
I
OUT
(A)
50
55
60
65
70
75
80
85
90
95
100
0.001 0.01 0.1 1
4.5VIN
3.5VIN
2.7VIN
3.0VIN
2.5VIN
November 12, 2014
FN8448.1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774
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