|
|
PDF SC471A Data sheet ( Hoja de datos )
| Número de pieza | SC471A | |
| Descripción | Synchronous Buck Controller | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de SC471A (archivo pdf) en la parte inferior de esta página. Total 27 Páginas | ||
|
No Preview Available !
PPOOWWEERRMMAANNAAGGEEMMEENNTT
SC471/SC471A
Synchronous Buck Controller with
Multi-Level VOUT Transition Support
Description
Features
The SC471/A is a versatile, constant on-time synchronous
buck, pseudo-fixed-frequency, PWM controller intended for
notebook computers and other battery operated portable
devices. The SC471/A contains all the features needed to
provide cost-effective control of system elements needing
voltage slewing. Two integrated switches provide four
resistor-programmable DC output voltages, controlled by
the G0 and G1 inputs.
www.DataSheet4U.com
The output voltage is adjustable from 0.75V to 5V.
Additional features for each output include cycle-by-cycle
current limit, voltage soft-start, under-voltage protection,
programmable over-current protection, soft shutdown,
automatic power save and non-overlapping gate drive.
The SC471/A provides an enable input and a power good
output which is automatically blanked during output
voltage transitions.
The constant on-time topology provides fast dynamic
response. The excellent transient response means that
SC471/A based solutions require less output capacitance
than competing fixed-frequency converters. Switching
frequency is constant until a step in load or line voltage
occurs, at which time the pulse density and frequency
will increase or decrease to counter the change in
output voltage. After the transient event, the controller
frequency returns to steady state operation. At light loads,
the automatic power save mode reduces the SC471/A
frequency for improved efficiency.
VOUT Programmable 0.75V to 5.25V with Integrated
Transition Support
VBAT Range 3V to 25V
Soft Shutoff at Output
Current Sense Using Low-side RDS(ON) or Resistor
Sensing
Adjustable Cycle-by-Cycle Valley Current Limit
325kHz Fixed-Frequency
Constant On-Time for Fast Dynamic Response and
Reduced Output Capacitance
Automatic Smart Power Save†
Internal Soft-Start
Over-Voltage/Under-Voltage Fault Protection
Power Good Output with Transition Blanking
1μA Typical Shutdown Current
500μA Typical Operating Current
Tiny 3×3mm, 16 Pin MLPQ Package
Low External Part Count
Industrial Temperature Range
0.85% Internal Reference
1A/3A Non-Overlapping Gate Drive with
SmartDriver™ Technology
High Efficiency > 90%
This Product is Fully WEEE and RoHS Compliant
†Patent Pending
Applications
Notebook/Sub-Notebook Graphics Voltage
Controllers
Tablet PCs
Embedded Applications
September 12, 2006
1
www.semtech.com
1 page  
SC471/SC471A
POWER MANAGEMENT
Electrical Characteristics (continued)
Parameter
Conditions
25°C
Min Typ Max
-40° to 85°C
Min Max
Units
Fault Protection (continued)
Output Under-Voltage Fault
FB with Respect to Nominal
Steady-State
Over-Voltage Fault
www.DataSheet4U.com
Steady-State
Over-Voltage Fault Delay
FB with Respect to Nominal
FB Forced 50mV Above
Over-Voltage Fault Threshold
G0/G1 Transition
Over-Voltage Fault
FB with Respect to Nominal;
valid for 32 cycles after G0/G1
Transition
Smart Power Save Threshold FB with Respect to Nominal
Over-Temperature Shutdown(1) Latching, >10°C Hysteresis
-30
+20
5
+50
+8
160
-35 -25 %
+17 +23 %
μs
%
%
°C
Logic Inputs/Outputs
Logic Input High Voltage
Logic Input Low Voltage
EN Input Bias Current
G0, G1 Input Bias Current
Power Good Output
Low Voltage
EN, G0, G1
EN, G0, G1
EN = 5V
G0, G1 = 5V
RPWRGD = 10kΩ to VCC
1.2 V
0.4 V
-1 +1 μA
5 0 10 μA
0.4 V
Gate Drivers
Shoot-Through
Protection Delay(1)
DH or DL Rising
30
ns
DL Pull-Down Resistance
0.8 1.6 Ω
DL Sink Current
DL Pull-Up Resistance
VDL = 2.5V
3.1
2
A
4Ω
DL Source Current
DH Pull-Down Resistance
VDL = 2.5V
BST - LX = 5V
1.3
2
A
4Ω
DH Pull-Up Resistance(2)
BST - LX = 5V
2
4Ω
DH Sink/Source Current
VDH = 2.5V
1.3
A
Notes:
1) Guaranteed by design.
2) Semtech’s SmartDriver™ FET drive first pulls DH high with a pull-up resistance of 10Ω (typical) until LX = 1.5V (typical). At this point, an ad-
ditional pull-up device is activated, reducing the resistance to 2Ω (typical). This negates the need for an external gate or boost resistor.
© 2006 Semtech Corp.
5
www.semtech.com
5 Page 
SC471/SC471A
POWER MANAGEMENT
Applications Information (continued)
3. The output over-voltage OVP point is raised to 50%
above nominal, or 1.125V at FB. When going from
a higher to lower voltage, the G0/G1 change causes
rapid change of D0/D1, which in turns cause a rapid
change at FB. The temporary increase in OVP allows
the output to slew down to the new level without
tripping the OVP function.
VOUT Voltage Selection
www.DataVSOheUeTt4Uvo.clotmage is regulated through the FB pin via resistors
R1 through R4 as shown in Figure 4.
R4 R3
FB
TON
0.75V
G1 Logic
G0 Control
D1 D0
SC471/A
R1
R2
VOUT
+
Figure 4
Voltage Transitioning
The G0/G1 pins allow VOUT to transition to both higher
and lower values. The two directions have differing
responses.
When doing a down transition, the D0/D1 change will
cause FB to go above the 0.75V threshold. Depending on
the level of VOUT change and the load, the IC responds in
different ways. At light load conditions when power-save
is active, and when the downward change is 8% or greater,
the rapid change of D0/D1 is large enough to cause FB
to rise up to the Smart Power Save threshold (810mV).
DL will drive high to turn on the low-side MOSFET and
draw current from the output capacitor via the inductor.
DL will remain on until FB falls to 0.75V, at which point
a normal DH switching cycle begins, see Figure 5. This
causes the output to transition to the new voltage level
quickly, typically 10~20 usec. Refer to the Smart Power
Save Protection section for a full description.
A rapid downward change in VOUT also occurs for downward
changes less than 8%, provided the load is high enough
such that power-save is not active. In this case, after D0
opens and FB rises above the 0.75V trip point, DL will drive
high and stay high until FB drops to the trip point.
The following table shows the equations that set VOUT as
a function of control inputs G0/G1:
VOUT Equation
SC471
G1 G0
0.75 • (1 + R1/R2)
00
0.75 • (1 + R1/R2 + R1/R3)
01
0.75 • (1 + R1/R2 + R1/R4)
10
0.75 • (1 + R1/R2 + R1/R3 + R1/R4) 1
1
SC471A
G1 G0
11
10
01
00
D0/D1
R3/R4
VOUT
R1
R2
FB
D0/D1
FB
DL
RTN
(Smart Psave threshold)
810mV
750mV
(FB threshold)
Note: the RDSON of the internal D0/D1 mosfets is in series
with R3/R4, which adds typically 15 ohms in series.
DL
VOUT
© 2006 Semtech Corp.
11
Figure 5
Initial VOUT
Final VOUT
www.semtech.com
11 Page | ||
| Páginas | Total 27 Páginas | |
| PDF Descargar | [ Datasheet SC471A.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| SC471 | Synchronous Buck Controller | Semtech Corporation |
| SC471A | Synchronous Buck 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 |