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EL7558BCM-T13 Schematic ( PDF Datasheet ) - Elantec Semiconductor

Teilenummer EL7558BCM-T13
Beschreibung Integrated Adjustable 8 Amp Synchronous Switcher
Hersteller Elantec Semiconductor
Logo Elantec Semiconductor Logo 




Gesamt 13 Seiten
EL7558BCM-T13 Datasheet, Funktion
EL7558BC
Integrated Adjustable 8 Amp Synchronous Switcher
Features
EL7558C/EL7558AC pin-
compatible
Improved temperature and voltage
ranges
8A continuous load current
Precision internal 1% reference
1.0V to 3.8V output voltage
Internal power MOSFETs
>90% efficiency
Synchronous switching
Adjustable slope compensation
Over-temperature indicator
Pulse-by-pulse current limiting
Operates up to 1MHz
1.5% typical output accuracy
Adjustable oscillator with sync
Remote enable/disable
Intel P54- and P55-compatible
VCC2DET interface
Internal soft-start
Applications
PC motherboards
Local high power CPU supplies
5V to 1.0V DC:DC conversion
Portable electronics/instruments
P54 and P55 regulators
GTL+ Bus power supply
Ordering Information
Part No
EL7558BCM
EL7558BCM-T13
Package
28-Pin HSOP
28-Pin HSOP
Tape &
Reel
-
13”
Outline #
MDP0042
MDP0042
General Description
The EL7558BC is an adjustable synchronous DC:DC switching regu-
lator optimized for a 5V input and 1.0V-3.8V output. By combining
integrated NMOS power FETS with a HSOP package the EL7558BC
can supply up to 8A continuous output current without the use of
external power devices or externally attached heat sinks, thereby min-
imizing design effort and overall system cost.
On-chip resistorless current sensing is used to achieve stable, highly
efficient, current-mode control. The EL7558BC also incorporates the
VCC2DET function to directly interface with the Intel P54 and P55
microprocessors. Depending on the state of VCC2DET, the output
voltage is internally preset to 3.50V or a user-adjustable voltage using
two external resistors. In both internal and external feedback modes
the active-high PWRGD output indicates when the regulator output is
within ±10% of the programmed voltage. An on-board sensor moni-
tors die temperature (OT) for over-temperature conditions and can be
connected directly to OUTEN to provide automatic thermal shutdown.
Adjustable oscillator frequency and slope compensation allow added
flexibility in overall system design.
The EL7558BC is available in the 28-pin HSOP package and is speci-
fied for operation over the -40°C to +85°C temperature range.
Connection Diagram
R4 R3
100
150
VIN
VIN
C4 0.1µF
C7 220pF
C8 330pF
R5
5.1
1 FB1
FB2 28
2 CREF
CP 27
3 CSLOPE C2V 26
4 COSC VSS 25
5 VDD
VHI 24
6 VIN
LX 23
7 VSSP
LX 22
C9
660µF
C12
1µF
C3
1µF
8 VIN
LX 21
9 VSSP
LX 20
10 VSSP VSSP 19
11 VSSP VSSP 18
D3
C5
R1 1µF
20
R6
C 6 39.2
0.1µF
D1
D2
L1 2.5µH
C10
1mF
Connect to VSSP for
external feedback
12 VSSP TEST 17
13
VCC2DET
PWRGD
16
14 OUTEN
OT 15
C12 = 1µF
C3, C4, C5, C6, C7 C8 - ceramic
C5, C11 - ceramic or tantalum
C9 - Sprague 293D337X96R3 2X330µF
C10 - Sprague 293D337X96R3 3X330µF
L1 - Pulse Engineering, PE-53681
D1 - D4: BAT54S fast diode
D4 Required for EL7558ACM only
EL7558BC
Manufactured under U.S. Patents No. 5,723,974 and No. 5,793,126
D4*
(Optional)
C11
0.22µF
VOUT
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.






EL7558BCM-T13 Datasheet, Funktion
EL7558BC
Integrated Adjustable 8 Amp Synchronous Switcher
Typical Performance Curves
IVDD + IVIN vs FOSC
60
TA=25°C
50 OUTEN=VDD
VDD=5.5V
40
30
VDD=4.5V
VDD=5V
20
10
Discontinuous Mode
0
FOSC (kHz)
Continuous Mode
IVDD vs FOSC
50
45 TA=25°C
40 OUTEN=VDD
35
30
25
20
15
10
5
0
VDD=5V
VDD=5.5V
VDD=4.5V
FOSC (kHz)
IQ vs FOSC
2.0
VDD=5.5V
VDD=5V
1.5
VDD=4.5V
1.0
10
100
FOSC (kHz)
1000
IVIN vs FOSC
16
14
TA=25°C
OUTEN=VDD
12
10
8
6
4
2
Discontinuous Mode
0
VDD=5.5V
VDD=5V
VDD=4.5V
Continuous Mode
FOSC (kHz)
RDSON vs Temperature
38
36
34
32
30
28
26
24
22
20
0 25 50 75
Temperature (°C)
100
125
Power On Reset
40
TA=25°C
OUTEN=VDD
30
20 FOSC=500k
10
0
2.5 3.0 3.5 4.0 4.5 5.0
VDD (V)
6

6 Page









EL7558BCM-T13 pdf, datenblatt
EL7558BC
Integrated Adjustable 8 Amp Synchronous Switcher
exceeds the thermal trip-point, the OT pin will output a
logic 0. The upper and lower trip points are set to 135 ºC
and 100ºC respectively. To enable thermal shutdown
this pin should be tied directly to OUTEN. Use of this
feature is recommended during normal operation
Power Good and Power On Reset
During power up the output regulator will be disabled
until VIN reaches 4.0V. Approximately 500mV of hys-
teresis is present to eliminate noise induced oscillations.
Under-voltage and over-voltage conditions on the regu-
lator output are detected through an internal window
comparator. A logic 1 on the PWRGD output indicates
that regulated output voltage is within ±10% of the nom-
inally programmed output voltage. Although small, the
typical values of the PWRGD threshold will vary with
changes to external feedback (and resultant loop gain) of
the system. This dependence is shown in the typical per-
formance curves.
Thermal Management
The EL7558BC utilizes HSOP packaging technology in
conjunction with the system board layout to achieve a
lower thermal resistance than typically found in standard
28 lead SOIC packages. By attaching the die directly to
an exposed metal slug embedded within the package
body, thermal energy flows through a thermally conduc-
tive path (metal) instead of thermally resistive plastic.
After conducting heat from the die to the PCB, heat
transfer occurs by convection. If a significant amount of
metal on the PCB is connected to the exposed heat slug,
a junction-to-ambient resistance of 31ºC/W can be
achieved compared to 100ºC/W found in standard pack-
ages. It can be readily seen that the thermal resistance
approaches an asymptotic value of approximately
31ºC/W. Additional information can be found in Appli-
cation Note #8 (Measuring the Thermal Resistance of
Power Surface-Mount Packages), and Application Note
#13 (EL75XX Thermal Design Considerations).
If the thermal shutdown pin is connected to OUTEN the
IC will enter thermal shutdown when the maximum
junction temperature is reached. For a thermal shutdown
of 135ºC and power dissipation of 2.2W the ambient
temperature is limited to a maximum value of 67ºC (typ-
ical). The ambient temperature range can be extended
with the application of air flow. For example, the addi-
tion of 100LFM reduces the thermal resistance by
approximately 15% and can extend the operating ambi-
ent to 77ºC (typical). Since the thermal performance of
the IC is heavily dependent on the board layout, the sys-
tem designer should exercise care during the design
phase to ensure that the IC will operate under the worst-
case environmental conditions.
12

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