|
|
PDF EL7571C Data sheet ( Hoja de datos )
| Número de pieza | EL7571C | |
| Descripción | Programmable PWM Controller | |
| Fabricantes | Elantec Semiconductor | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de EL7571C (archivo pdf) en la parte inferior de esta página. Total 23 Páginas | ||
|
No Preview Available !
EL7571C
Programmable PWM Controller
Features
General Description
• Pentium® II Compatible
• 5 bit DAC Controlled Output Voltage
• Greater than 90% Efficiency
• 4.5V to 12.6V Input Range
• Dual NMOS Power FET Drivers
• Fixed frequency, Current Mode
Control
• Adjustable Oscillator with External
Sync. Capability
• Synchronous Switching
• Internal Soft-Start
• User Adjustable Slope
Compensation
• Pulse by Pulse Current Limiting
• 1% Typical Output Accuracy
• Power Good Signal
• Output Power Down
• Over Voltage Protection
Applications
• Pentium® II Voltage Regulation
Modules (VRMs)
• PC Motherboards
• DC/DC Converters
• GTL Bus Termination
• Secondary Regulation
Ordering Information
Part No
EL7571C
Temp. Range
0°C to +70°C
Package
20-Pin SO
Outline #
MDP0027
The EL7571C is a flexible, high efficiency, current mode, PWM step
down controller. It incorporates five bit DAC adjustable output voltage
control which conforms to the Intel Voltage Regulation Module (VRM)
Specification for Pentium® II and Pentium® Pro class processors. The
controller employs synchronous rectification to deliver efficiencies
greater than 90% over a wide range of supply voltages and load condi-
tions. The on-board oscillator frequency is externally adjustable, or may
be slaved to a system clock, allowing optimization of RFI performance in
critical applications. In single supply operation, the high side FET driver
supports boot-strapped operation. For maximum flexibility, system oper-
ation is possible from either a 5V rail, a single 12V rail, or dual supply
rails with the controller operating from 12V and the power FETs from
5V.
Connection Diagram
ENABLE
1 OTEN
C3 240pF
2 CSLOPE
C3 240pF
3 COSC
1.4V C3
0.1µF
4 REF
POWER
GOOD
5 PWRGD
6 VIDO
Voltage
I.D.
(VID
(0:4))
7 VID1
8 VID2
9 VID3
VH1 20
HSD 19
LX 18
VIN 17
VINP 16
LSD 15
GNDP 14
GND 13
CS 12
R2
5Ω
D1
C6 0.1µF
Q1 C8
1µF
L2
C1 1.5µH
1000µF
x3
4.5V
to
12.6V
VOUT
1.3V to
L1 R2 3.5V
C7 5.1µH 5Ω
1µF
Q2 D2
C2
1000µF
x6
10 VID4
FB 11
Q1, Q2: Siliconix, Si4410, x2
C1: Sanyo, 16MV 1000GX, 1000µF x3
C2: Sanyo, 6MV 1000GX, 1000µF x6
L1: Pulse Engineering, PE-53700, 5.1µH
L2: Micrometals, T30-26, 7T AWG #20, 1.5µH
R1: Dale, WSL-25-12, 15mΩ, x2
D1: BAV99
D2: IR, 32CTQ030
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.
1 page  
Typical Performance Curves
+5V Supply Sync with Schottky Load
2.5
1.5 VOUT = 3.5V
VOUT = 2.8V
0.5
0
-0.5 VOUT = 1.8V
-1.5 VOUT = 1.3V
-2.5
0 1 3 5 7 9 11
IOUT(A)
+5V Supply Non-Sync VRM Efficiency
1.0
13
0.9
0.8
VOUT = 3.5V
0.7
VOUT = 2.8V
0.6 VOUT = 1.8V
VOUT = 1.3V
0.5
0 1 3 5 7 9 11 13
IOUT(A)
12V Transient Response
EL7571C
Programmable PWM Controller
+5V Supply +12V Controller Sync w/o Schottky
VRM Efficiency
1.0
0.9
0.8
VOUT = 3.5V
0.7 VOUT = 1.8V
0.6
VOUT = 2.8V
VOUT = 1.3V
0.5
0.02 1.02 3.04 5.04 7.04 9.04 11.04 13.04
IOUT(A)
+5V Supply Sync with Schottky VRM Efficiency
1.0
0.9
0.8
VOUT = 3.5V
0.7
VOUT = 2.8V
0.6 VOUT = 1.8V
VOUT = 1.3V
0.5
013579
IOUT(A)
5V Non-sync Transient Response
11 13
11
5
5 Page 
EL7571C
Programmable PWM Controller
For safe and reliable operation, PD must be less than the
capacitor’s data sheet rating.
Input Inductor, L2
The input inductor (L2) isolates switching noise from
the input supply line by diverting buck converter input
ripple current into the input capacitor. Buck regulators
generate high levels of input ripple current because the
load is connected directly to the supply through the top
switch every cycle, chopping the input current between
the load current and zero, in proportion to the duty cycle.
The input inductor is critical in high current applications
where the ripple current is similarly high. An exclu-
sively large input inductor degrades the converter’s load
transient response by limiting the maximum rate of
change of current at the converter input. A 1.5µH input
inductor is sufficient in most applications.
Output Capacitor, C2
During steady state operation, output ripple current is
much less than the input ripple current since current flow
is continuous, either via the top switch or the bottom
switch. Consequently, output capacitor power dissipa-
tion is less of a concern than the input capacitor’s.
However, low ESR is still required for applications with
very low output ripple voltage or transient response
requirements. Output ripple voltage is given by:
VRIP = IRIP × ESROUT
where:
IRIP = output ripple current
ESROUT = output capacitor ESR
During a transient response, the output voltage spike is
determined by the ESR and the equivalent series induc-
tance (ESL) of the output capacitor in addition to the rate
of change and magnitude of the load current step. The
output voltage transient is given by:
∆VOUT
=
E
S
RO
U
T
×
∆IOUT
+
ESL
×
dd----it
where:
ESROUT = output capacitor ESR
ESL = output capacitor ESL
∆IOUT = output current step
di/dt = rate of change of output current
Power MOSFET, Q1 and Q2
The EL7571C incorporates a boot-strap gate drive
scheme to allow the usage of N-channel MOSFETs. N-
channel MOSFETs are preferred because of their rela-
tive low cost and low on resistance. The largest amount
of the power loss occurs in the power MOSFETs, thus
low on resistance should be the primary characteristic
when selecting power MOSFETs. In the boot-strap gate
drive scheme, the gate drive voltage can only go as high
as the supply voltage, therefore in a 5V system, the
MOSFETs must be logic level type, Vgs<4.5V. In addi-
tion to on resistance and gate to source threshold, the
gate to source capacitance is also very important. In the
region when the output current is low (below5A),
switching loss is the dominant factor. Switching loss is
determined by:
P = C × V2 × F
where:
C is the gate to source capacitance of the MOSFET
V is the supply voltage
F is the switching frequency
Another undesirable reason for a large MOSFET gate to
source capacitance is that the on resistance of the MOS-
FET driver can not supply the peak current required to
turn the MOSFET on and off fast. This results in addi-
tional MOSFET conduction loss. As frequency
increases, this loss also increases which leads to more
power loss and lower efficiency.
Finally, the MOSFET must be able to conduct the maxi-
mum current and handle the power dissipation.
The EL7571C is designed to boot-strap to 12V for 12V
only input converters. In this application, logic level
MOSFETs are not required.
Table below lists a few popular MOSFETs and their crit-
ical specifications.
11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet EL7571C.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| EL7571C | Programmable PWM Controller | Elantec Semiconductor |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |