Datasheet

600 mA, 6 MHz, Synchronous
Step-Down DC-to-DC Converter
ADP2121
Rev. B
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FEATURES
Peak efficiency: 92%
Operating frequency: 6 MHz
Typical quiescent current in auto mode: 36 µA
Fixed output voltage: 1.8 V, 1.82 V, 1.85 V, 1.875 V, 2.3 V
Maximum guaranteed load current: 600 mA at V
IN
= 2.7 V to 5.5 V
Input voltage: 2.3 V to 5.5 V
Typical shutdown supply current: 0.3 µA
Automatic power-saving mode
Compatible with tiny multilayer inductors
Internal synchronous rectifier
Internal compensation
Internal soft start
Output to ground short-circuit protection
Cycle-by-cycle current-limit protection
Enable/shutdown logic input
Undervoltage lockout
Thermal shutdown protection
Ultrasmall 6-ball, 0.4 mm pitch, 1.17 mm
2
WLCSP
APPLICATIONS
Mobile phones
Digital cameras
Digital audio
Portable equipment
GENERAL DESCRIPTION
The ADP2121 is a high frequency, low quiescent current
step-down dc-to-dc converter optimized for portable applications
in which board area and battery life are critical constraints. The
6 MHz operating frequency enables the use of tiny ceramic induc-
tors and capacitors. Additionally, the synchronous rectification
improves efficiency and results in fewer external components.
At high load currents, the device uses a voltage regulating pulse-
width modulation (PWM) mode that maintains a constant
frequency with excellent stability and transient response. In forced
PWM mode, the converter continues operating in PWM for light
loads. At light load conditions in auto mode, the ADP2121 can
automatically enter a power-saving mode that uses pulse-frequency
modulation (PFM) to reduce the effective switching frequency and
ensure the longest battery life in portable applications. During logic
controlled shutdown (EN ≤ 0.4 V), the input is disconnected
from the output and draws less than 0.3 μA current (typical)
from the source.
TYPICAL APPLICATION CIRCUIT
VIN
07407-001
GND
MODE
EN
FB
SW
C
IN
2.2µF
C
OUT
4.7µF
ADP2121
L
0.47µH
ON
OFF
PWM
AUTO
B2
C1
A2
C2
A1
B1
OUTPUT VOLTAGE
1.8V, 1.82V, 1.85V, 1.875V, 2.3V
INPUT VOLTAGE*
2.3V TO 5.5V
*FOR OUTPUT VOLTAGE = 2.3 V, INPUT VOLTAGE = 2.9 V TO 5.5V.
Figure 1.
TYPICAL PERFORMANCE
07407-062
55
0.1 1 10 100 1000
65
75
85
95
LOAD CURRENT (mA)
V
OUT
= 1.8V
V
OUT
= 1.82V
V
OUT
= 1.85V
V
OUT
= 1.875V
V
OUT
= 2.3V
AUTO MODE
V
IN
= 2.7 V
(V
IN
= 2.9V FOR V
OUT
= 2.3V)
EFFICIENCY (%)
Figure 2. Efficiency vs. Load Current for Each Voltage Option
The ADP2121 has an input voltage range of 2.3 V to 5.5 V (2.9 V
to 5.5 V for V
OUT
= 2.3 V), allowing the use of a single Li+/Li−
polymer cell, 3-cell alkaline or Ni-MH cell, and other standard
power sources. The converter can source up to 600 mA and is
internally compensated to minimize external components. Other
key features, such as cycle-by-cycle peak current limit, soft start,
undervoltage lockout (UVLO), output-to-ground short-circuit
protection, and thermal shutdown, protect the internal and
external circuit components.
Table 1. Output Voltage Options
Input Voltage
Range (V)
Typical Start-Up
Time (μs)
Fixed Output
Voltage (V)
2.3 to 5.5 75 1.8, 1.85, 1.875
2.3 to 5.5 275 1.82
2.9 to 5.5 100 2.3