|
|
PDF SC2620 Data sheet ( Hoja de datos )
| Número de pieza | SC2620 | |
| Descripción | 30V Step-down Regulator | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de SC2620 (archivo pdf) en la parte inferior de esta página. Total 26 Páginas | ||
|
No Preview Available !
SC2620
Dual 2A, 30V Step-down Regulator with
Programmable Frequency up to 1.4MHz
POWER MANAGEMENT
Deswcwrwi.pDtaitaoSnheet4U.com
Features
The SC2620 is a constant frequency dual current-mode
switching regulator with integrated 2.3A, 30V switches.
Its switching frequency can be programmed up to 1.4MHz
per channel. Due to the SC2620’s high frequency
operation, small inductors and ceramic capacitors can be
used, resulting in very compact power supplies. The two
channels of the SC2620 operate at 180° out of phase for
reduced input voltage ripples.
Separate soft start/enable pins allow independent control
of each channel. Channel 1 power good indicator can be
used for output start up sequencing to prevent latch-up.
Current-mode PWM control achieves fast transient
response with simple loop compensation. Cycle-by-cycle
current limiting and hiccup overload protection reduce
power dissipation during overload.
Wide Input Voltage Range 2.8V to 30V
Up to 1.4MHz/Channel Programmable Switching
Frequency
Current-mode Control
Out of Phase Switching Reduces Ripple
Cycle-by-cycle Current-limiting
Independent Shutdown/soft-start Pins
Independent Hiccup Overload Protection
Channel 1 Power Good Indicator
Two 2.3A Integrated Switches
Thermal Shutdown
Thermally Enhanced SO-16 Lead Free Package
Fully WEEE and RoHS Compliant
Applications
XDSL and Cable Modems
Set-top Boxes
Point of Load Applications
CPE Equipment
DSP Power Supplies
Typical Application Circuit
R5 C5
12.7k C6 1.5nF
C7 47pF
22nF R9
46. 4 k
C10
22nF
C9
R7 33pF C8
10.5k 4.7nF
FB1
COMP1 BOOST1
SS1
SW1
ROSC
SC2620
PGOOD1 PVIN
SS2
VIN
COMP2
SW2
FB2 BOOST2
GND
D3
9V-16V VIN
C15
R10 10µF
10
C2 1N4148
0.1µF L1
10µH
D1
UPS120
C1
22µF
R1
30. 1 k
R2
13k
OUT1
3.3V /2A
C16
0.1µF
D4
1N4148
D2
UPS120
L2
C4
0.1µF
6.8µH
OUT2
C3
22µF
R3 1.2V/2A
2.6 1 k
R4
13k
V IN = 1 2 V
CH1
CH2
CH3
4ms/div
CH1 : OUT1 Voltage, 2V/div
CH2 : OUT2 Voltage, 1V/div
CH3 : SS2 Voltage, 2V/div
L1 & L2: Coiltr onics DR73
C1 & C3: Murata GRM21BR60J 226M
C15: Murata GRM32DR61E106K
Figure
1(a).
550kHz 9V-16V
down Converter.
VIN
to
3.3V
and
1.2V
Step-
Figure 1(b). V0IN.8SAt)a.rCt-huapnTnrealn2siestnatr(tIOisUT1d=el1a.y5eAd, uIOnUtTi2l=
Channel 1 reaches regulation.
Revision: July 30, 2008
1
www.semtech.com
1 page  
SC2620
POWER MANAGEMENT
BlowcwkwD.DaiatagShreaemt4Us.com
PGOOD1
15
COMP1
16
FB1
1
SS1
14
CHANNEL 1 ONLY
-
+
POWER
GOOD
100m V
-
EA
+
+
PWM
-
+
Σ
+
SLOPE
COMP 1
+
ISEN
-
+
ILIM
-
20mV
BOOST1
2
4 PVIN1
6.3mΩ
S
Q
R
POWER
TRANSISTOR
FB1
3 SW1
Soft-Start
1V 0.7V
And
Overload
OVLD
SS2
10
REFERE NCE
& THERMAL
SHUTDOWN
FAULT
Hiccup
Control 1
12 VIN
SLOPE SLOPE
COMP 1 COMP 2
ROSC
13
OSCILLATOR
SLOPE COMP
CLK1
FREQUENC Y
DIVIDER CLK2
Figure 2. SC2620 Block Diagram (Channel 1)
11 GND
FB
0.7V
SS
+
-
1.8µA
1V/2V
S
Q
R
OVLD
FAULT
2.6µA
2008 Semtech Corp.
Figure 3. Details of the Soft-Start and Overload Hiccup Control Circuit
5
www.semtech.com
5 Page 
SC2620
POWER MANAGEMENT
Appwlwicwa.DtaitoaSnhseeItn4Uf.ocormmation
L
=
(VOUT
+ 0.45)(VIn − VOUT − 0.25)
(VIN + 0.2)(0.69)f
(4)
where L is in µH and f is in MHz.
Equation (3) shows that for a given VOUT , ∆IL increases as
D decreases. If VIN varies over a wide range, then choose
L based on the nominal input voltage. Always verify
converter operation at the input voltage extremes.
The peak current limits of both SC2620 power transistors
are internally set at 3.2A. The peak current limits are duty-
cycle invariant and are guaranteed higher than 2.3A. The
maximum load current is therefore conservatively:
IOUT (MAX )
= ILM
−
∆IL
2
= 2.3A −
∆IL
2
(5)
If ∆IL = 0.3 ⋅ILM , then
IOUT(MAX)
= ILM −
∆IL
2
= ILM −
0.3ILM
2
= 0.85 ⋅ILM .
Power
dissipated
in
the
input
capacitor
is
I2
RMS(CIN)
⋅ (ESR)
.
Equation
(6)
has
a
maximum
value
of
IOUT
2
( at
D
=
1
2
),
corresponding to the worst-case power dissipation
I2OUT ⋅ESR
4
in CIN.
A dual-channel step-down converter with interleaved
switching reduces the RMS ripple current in the input
capacitor to a fraction of that of a single-phase buck
converter. If both power transistors in the SC2620 were
to switch on in phase, the current drawn by the SC2620
would consist of current pulses with amplitude equal to
the sum of the channel output currents. If each channel
twheereindpeultivceurrirnegnItOwUToaunldd
operating at 50% duty cycle,
switch from zero to 2IOUT. The
then
RMS
ripple current in the input capacitor would then be IOUT.
Power dissipated in CIN would be I2OUT ⋅ESR , 4 times that
of a single-channel converter. The SC2620 produces the
highest RMS ripple current in CIN when only one channel is
running and delivering the maximum output current (2A).
The input capacitor therefore should have a RMS ripple
current rating of at least 1A.
The saturation current of the inductor should be 20-30%
higher than the peak current limit (2.3A). Low-cost powder
iron cores are not suitable for high-frequency switching
power supplies due to their high core losses. Inductors
with ferrite cores should be used.
Power Line Input Capacitor
A buck converter draws pulse current with peak-to-peak
amplitude equal to its output current IOUT from its input
supply. An input capacitor placed between the supply and
the buck converter filters the AC current and keeps the
current drawn from the supply to a DC constant. The input
capacitance CIN should be high enough to filter the pulse
input current. Its equivalent series resistance (ESR) should
be low so that power dissipated in the capacitor does not
result in significant temperature rise and degrade reliability.
For a single channel buck converter, the RMS ripple current
in the input capacitor is
IRMS(CIN) = IOUT D(1 − D) .
(6)
Multi-layer ceramic capacitors, which have very low ESR
(a few mΩ) and can easily handle high RMS ripple current,
are the ideal choice for input filtering. A single 4.7µF or
10µF X5R ceramic capacitor is adequate. For high voltage
applications, a small ceramic (1µF or 2.2µF) can be placed
in parallel with a low ESR electrolytic capacitor to satisfy
both the ESR and bulk capacitance requirements.
Output Capacitor
The output ripple voltage ∆VOUT of a buck converter can be
expressed as
∆VOUT
=
∆IL ESR +
1
8fCOUT
(7)
where COUT is the output capacitance.
(InEdquuacttioornr(i3pp))l.eThceuroruetnptu∆t IrLipipnlcerevaoslteasgeaiss
D decreases
therefore the
highest when VIN is at its maximum. The first term in (7)
results from the ESR of the output capacitor while the
2008 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet SC2620.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| SC2620 | 30V Step-down Regulator | Semtech Corporation |
| SC2621 | 500kHz Voltage Mode PWM Controller | Semtech Corporation |
| SC2621A | Voltage Mode PWM Controller | Semtech Corporation |
| 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 |