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PDF SC4620 Data sheet ( Hoja de datos )
| Número de pieza | SC4620 | |
| Descripción | 2.5A Integrated FET Synchronous Step down DC/DC Regulator | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
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SC4620
Low Input Voltage, High Efficiency, 2.5A Integrated
FET Synchronous Step down DC/DC Regulator
POWER MANAGEMENT
Description
Features
The SC4620 is a highly integrated synchronous step-down
DC/DC regulator designed for low input voltage range of
2.3V to 5.5 Volts. It can deliver 2.5A continuous output
current with the output voltage as low as 0.5 Volts. The
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eliminate
delivering
overall converter efficiency up to 95%.
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output voltage
from 200 kHz
to 2MHz with a single resistor and it can be synchronized
to an external clock.
The SC4620 offers adjustable current limit, soft start and
over temperature protection to safeguard the device under
extreme operating conditions. The soft start provides a
controlled output voltage ramp up at startup. When a
logic low is applied to the Enable pin, the SC4620 enters
the shutdown mode and it consumes less than 1µA of
current.
The SC4620 is available in 4x4 MLPQ-20 and it is rated
over -40°C to +85°C ambient temperature range.
u VIN Range: 2.3 – 5.5V
u 2.5A Continuous Output Current
u Adjustable Output Voltage 0.5V to Vin
u Up to 95% Efficiency
u Synchronizable and Programmable Frequency:
200kHz – 2MHz
u Power Good Monitor
u <1µA of Shutdown Current
u Programmable Soft Start
u Programmable Current Limit
u Over Temperature protection
u -40 to +85 °C Ambient Temperature Range
u 4X4mm MLPQ-20 packages- WEEE and RoHS
compliant
Applications
Low Voltage Distributed DC-DC Converters
Telecommunication Power Supplies
Portable Equipment
xDSL
Typical Application Circuit
5
D
Vin
C9
C
4
R4
3
C11
R5
R6
R2
C3
PVIN
SYNC/EN
PGOOD
VCC
PH
FB
SC4620
SS
B ISET
FS COMP
C7 C5 R3 R11
21
L1 Vout
R7
R8
C8
C4
R1 R9
C1 L2
C2
D
C
B
A
Revision: June 25, 2007
5
43
A
21
www.semtech.com
1 page  
SC4620
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless otherwise specified, VIN= VCC=SYNC/EN=3.3V, ROSC=51.1KΩ, RISET=27.4KΩ, TA = -40°C to 85°C.
Parameter
Symbol
Conditions
Min Typ Max Units
Error Amplifier (Cont.)
Output Voltage Low, COMP
Feedback Voltage
www.DataSheet4U.com
Input Bias Current(1)
Power Switches
VFB
IFB
FB = 0.6V, ICOMP = 1mA
Vcc = 2.3V to 5.5V
FB=VREF
0.1 0.25
V
0.4925 0.5 0.5075 V
-2 +1 +2 %
60 nA
High-Side P-MOSFET
Low Side N-MOSFET
Power Good
RDSH(on)
RDSL(on)
VIN=VCC=5V, ISOURCE = 1A, TA=TJ=25 °C
VIN=VCC=5V, ISINK = 1A, TA=TJ=25 °C
74 100 mΩ
47 85 mΩ
PGood Voltage Low
PGood Leakage Current
PGood Delay Time(1)
PGood High Window
VPGL
IPGOOD
TD
IPGOOD = 1mA
PGOOD = 5V
Vout rising or Vout falling
With respect to nominal output,
TA=TJ=25 °C
0.2 V
1 µA
1024
clks
+8 +10 +15 %
Note:
(1) Guaranteed by design.
2007 Semtech Corp.
www.semtech.com
5 Page 
SC4620
POWER MANAGEMENT
Application Information
Overview
The SC4620 is a programmable high switching frequency,
integrated 2.5A MOSFET, synchronous step down regula-
tor. This reduces external component count and makes it
effective for applications which are low in cost and sized
small. A non-overlap protection is provided for the gate
drive signals to prevent shoot through of the internal
MOSFET pair.
During start up or restart, A typical 6µA sourcing current
charges the capacitor and then the voltage of capacitor
ramp up the error amp reference slowly. The closed
loop creates narrow width driver pulses while the output
voltage is low and allows these pulses to increase to their
steady state duty cycle as the output voltage reaches
its regulated value. The duration of the soft start in the
SC4620 is controlled by an external capacitor.
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output voltage as
is programmable
up to 2MHz by an external resistor. It features lossless
current sensing of the voltage drop across the internal
drain to source resistance of the high side MOSFET during
its conduction period.
The quiescent supply current in shutdown mode is
typically lower than 1µA. An external soft start is provided
to prevent output voltage overshoot during start-up. Over
Temperature Protection, Power Good Indicator, External
Clock Synchronization are some of the internal added
features.
Enable
The SC4620 is enabled by applying a voltage greater than
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the internal soft start
no faults are present,
voltage low
the SC4620
uwniltlilinViCtCiarteeaachseosft2sVta. rItf
when
UVLO
cVoCCmepxacreaetodrs
2V. A typical 120mV hysteresis in the
provides noise immunity during its start
up. (refer to Figure 1 to 2).
Shutdown
Tohr eshSuCt4d6o2w0nismdoisdaebolepdewrahtieonnViCsC
falls below 1.88V (typical)
invoked by clamping the
SYNC/EN pin to a voltage below 0.8V. During the shutdown
mode, A typical
the internal soft
0.2µA current draw
start voltage is held
through
low and
the
the
iVnCtCerpnina,l
MOSFETs are turned off. (refer to Figure 3 to 4).
Soft Start
The soft start function is required for step down controllers
to prevent excess in-rush current through the DC bus
during start up. An external capacitor is necessary for
the soft start function and is connected from SS pin to
AGND.
The SC4620 starts up in asynchronous mode before SS
voltage reaches to 0.5V, and the bottom FET diode is used
for circulating current during the top FET off time. Ths SS
voltage level is clamped at VCC finally.
Oscillator
The FS pin is used to set the PWM oscillator frequency
through an external resistor that is connected from the
FS pin to the AGND. The internal ramp is a triangle at the
PWM frequency with a peak voltage of 1.25V and a valley
voltage of 0.25V. The approximate operating frequency is
determined by the value of an external resistor as shown
in Figure 15.
145
135
125
115
105
95
85
75
65
55
45
35
25
15
5
200
Switching Frequency Setting
5VIN
2.5VIN
400 600 800 1000 1200 1400 1600 1800 2000
Fosc (kHz)
Figure 15. Switching Frequency vs. RFS
The operation frequency can be programmed up to 2MHz,
but there is a minimum on-time limitation which is around
110ns. Users should take care of minimum limitation on the
operating duty cycle under high frequency application.
2007 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet SC4620.PDF ] | |
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