EL7551C - Preliminary
Monolithic 1 Amp DC:DC Step-down Regulator
Features
General Description
• Integrated synchronous MOSFETs
and current mode controller
• 1A continuous output current
• Up to 95% efficiency
• 4.5V to 5.5V input voltage
• Adjustable output from 1V to 3.8V
• Cycle-by-cycle current limit
• Precision reference
• ±0.5% load and line regulation
• Adjustable switching frequency to
1MHz
• Oscillator synchronization
possible
• Internal soft start
The EL7551C is an integrated, synchronous step-down regulator with
output voltage adjustable from 1.0V to 3.8V. It is capable of delivering
1A continuous current at up to 95% efficiency. The EL7551C operates
at a constant frequency pulse width modulation (PWM) mode, making
external synchronization possible. Patented on-chip resistorless cur-
rent sensing enables current mode control, which provides cycle-by-
cycle current limiting, over-current protection, and excellent step load
response. The EL7551C is available in a fused-lead 16-pin QSOP
package. With proper external components, the whole converter fits
into a less than 0.4 in2 area. The minimal external components and
small size make this EL7551C ideal for desktop and portable
applications.
The EL7551C is specified for operation over the -40°C to +85°C tem-
perature range.
• Over temperature protection
• Under voltage lockout
• 16-pin QSOP package
Applications
Typical Application Diagram
• DSP, CPU Core and IO Supplies
• Logic/Bus Supplies
• Portable Equipment
• DC:DC Converter Modules
• GTL + Bus Power Supply
1
2
3
4
5
6
7
8
SGND
COSC
VDD
PGND
PGND
VIN
PGND 16
VREF 15
FB 14
C3
C4
C5
0.1µF 270pF
Ordering Information
0.1µF
R3
R2
Part No
Package
Tape & Reel
Outline #
R1
39W
2.37k
EL7551CU
16-Pin QSOP
MDP0040
1kW
VDRV 13
LX 12
L1
C1
10µH
C
7
V
O
C6
(3.3V,
1A)
10µF
ceramic
47µF
LX 11
0.1µF
VIN
VHI 10
V
(4.5V-
5.5V)
IN
EN
PGND 9
EL7551C
Manufactured under U.S. Patent No. 57,323,974
Note: All information contained in this data sheet has been carefully checked and is believed to be accurate as of the date of publication; however, this data sheet cannot be a “controlled document”. Current revisions, if any, to these
specifications are maintained at the factory and are available upon your request. We recommend checking the revision level before finalization of your design documentation.
© 2001 Elantec Semiconductor, Inc.