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EL7532 Schematic ( PDF Datasheet ) - Intersil Corporation

Teilenummer EL7532
Beschreibung Monolithic 2A Step-Down Regulator
Hersteller Intersil Corporation
Logo Intersil Corporation Logo 




Gesamt 8 Seiten
EL7532 Datasheet, Funktion
®
Data Sheet
December 8, 2006
EL7532
FN7435.7
Monolithic 2A Step-Down Regulator
The EL7532 is a synchronous, integrated FET 2A step-down
regulator with internal compensation. It operates with an
input voltage range from 2.5V to 5.5V, which accommodates
supplies of 3.3V, 5V, or a single Li-Ion battery source. The
output can be externally set from 0.8V to VIN with a resistive
divider.
The EL7532 features PWM mode control. The operating
frequency is typically 1.5MHz. Additional features include a
100ms Power-On-Reset output, <1µA shut-down current,
short-circuit protection, and over-temperature protection.
The EL7532 is available in the 10-pin MSOP package,
making the entire converter occupy less than 0.18 in2 of
PCB area with components on one side only. The package is
specified for operation over the full -40°C to +85°C
temperature range.
Ordering Information
PART TAPE &
PKG.
PART NUMBER MARKING REEL PACKAGE DWG. #
EL7532IY
www.DataSheet4U.comEL7532IY-T7
BABAA
BABAA
- 10 Ld MSOP MDP0043
7” 10 Ld MSOP MDP0043
EL7532IY-T13 BABAA
13” 10 Ld MSOP MDP0043
EL7532IYZ
(Note)
BAARA
- 10 Ld MSOP MDP0043
(Pb-free)
EL7532IYZ-T7 BAARA
(Note)
7” 10 Ld MSOP MDP0043
(Pb-free)
EL7532IYZ-T13 BAARA
(Note)
13” 10 Ld MSOP MDP0043
(Pb-free)
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
Pinout
EL7532 (10 LD MSOP)
TOP VIEW
1 SGND
2 PGND
3 LX
4 VIN
5 VDD
FB 10
VO 9
POR 8
EN 7
RSI 6
Features
• 2A continuous current (from -40°C to +85°C)
• Less than 0.18 in2 footprint for the complete 2A converter
• Max height 1.1mm MSOP10
• 1.5MHz (typ.) switching frequency
• 100ms Power-On-Reset output (POR)
• Internally-compensated voltage mode controller
• Up to 94% efficiency
• <1µA shut-down current
• Overcurrent and over temperature protection
• Pb-free plus anneal available (RoHS compliant)
Applications
• PDA and pocket PC computers
• Bar code readers
• ADSL modems
• Portable instruments
• Li-Ion battery powered devices
• ASIC/FPGA/DSP supplies
• Set top boxes
Typical Application Schematic
VS (2.5V to 5.5V)
L1
R3 100Ω
C2 C3
VIN
VDD
LX 1.8µH
C1
10µF
10µF
0.1µF
EL7532
VO
R5 100kΩ
R4 100kΩ
R6
100kΩ
POR
EN
RSI
PGND
SGND
R1*
124kΩ
FB
R2*
100kΩ
C4
470pF
VO (1.8V @ 2A)
* VO = 0.8V * (1 + R1 / R2)
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2004, 2005, 2006. All Rights Reserved.
All other trademarks mentioned are the property of their respective owners.






EL7532 Datasheet, Funktion
EL7532
Applications Information
Product Description
The EL7532 is a synchronous, integrated FET 2A step-down
regulator which operates from an input of 2.5V to 6V. The
output voltage is user-adjustable with a pair of external
resistors.
The internally-compensated controller makes it possible to
use only two ceramic capacitors and one inductor to form a
complete, very small footprint 2A DC-DC converter.
Start-Up and Shut-Down
When the EN pin is tied to VIN, and VIN reaches
approximately 2.4V, the regulator begins to switch. The
output voltage is gradually increased to ensure proper soft-
start operation.
When the EN pin is connected to a logic low, the EL7532 is
in the shut-down mode. All the control circuitry and both
MOSFETs are off, and VOUT falls to zero. In this mode, the
total input current is less than 1µA.
When the EN reaches logic HI, the regulator repeats the
start-up procedure, including the soft-start function.
PWM Operation
In the PWM mode, the P channel MOSFET and N channel
MOSFET always operate complementary. When the
PMOSFET is on and the NMOSFET off, the inductor current
increases linearly. The input energy is transferred to the
output and also stored in the inductor. When the P channel
MOSFET is off and the N channel MOSFET on, the inductor
current decreases linearly, and energy is transferred from
the inductor to the output. Hence, the average current
through the inductor is the output current. Since the inductor
and the output capacitor act as a low pass filter, the duty
cycle ratio is approximately equal to VO divided by VIN.
The output LC filter has a second order effect. To maintain
the stability of the converter, the overall controller must be
compensated. This is done with the fixed internally
compensated error amplifier and the PWM compensator.
Because the compensations are fixed, the values of input
and output capacitors are 10µF to 22µF ceramic. The
inductor is nominally 1.8µH, though 1.5µH to 2.2µH can be
used.
100% Duty Ratio Operation
EL7532 utilizes CMOS power FET's as the internal
synchronous power switches. The upper switch is a PMOS
and lower switch a NMOS. This not only saves a boot
capacitor, it also allows 100% turn-on of the upper PFET
switch, achieving VO close to VIN. The maximum achievable
VO is,
VO = VIN (RL + RDSON1) × IO
Where RL is the DC resistance on the inductor and RDSON1
the PFET on-resistance, nominal 70mΩ at room temperature
with tempco of 0.2mΩ/°C.
As the input voltage drops gradually close or even below the
preset VO, the converter gets into 100% duty ratio. At this
condition, the upper PFET needs some minimum turn-off
time if it is turned off. This off-time is related to input/output
conditions. This makes the duty ratio appear randomly and
increases the output ripple somewhat until the 100% duty
ratio is reached. A larger output capacitor could reduce the
random-looking ripple. Users need to verify if this condition
has an adverse effect on the overall circuit if close to 100%
duty ratio is expected.
RSI/POR Function
When powering up, the open-collector Power-On-Reset
output holds low for about 100ms after VO reaches the
preset voltage. When the active-HI reset signal RSI is
issued, POR goes to low immediately and holds for the
same period of time after RSI comes back to LOW. The
output voltage is unaffected. (Please refer to the timing
diagram). When the function is not used, connect RSI to
ground and leave open the pull-up resister R4 at POR pin.
The POR output also serves as a 100ms delayed Power
Good signal when the pull-up resister R4 is installed. The
RSI pin needs to be directly (or indirectly through a resister
R5) connected to Ground for this to function properly.
VO
RSI
POR
100ms
MIN
25ns
100ms
FIGURE 13. RSI & POR TIMING DIAGRAM
Output Voltage Selection
Users can set the output voltage of the converter with a
resister divider, which can be chosen based on the following
formula:
VO
=
0.8
×
1
+
R-R----21- ⎠⎟⎞
Component Selection
Because of the fixed internal compensation, the component
choice is relatively narrow. We recommend 10µF to 22µF
multi-layer ceramic capacitors with X5R or X7R rating for
both the input and output capacitors, and 1.5µH to 2.2µH
inductance for the inductor.
6 FN7435.7
December 8, 2006

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