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PDF SC419 Data sheet ( Hoja de datos )
| Número de pieza | SC419 | |
| Descripción | DC-DC Converter | |
| Fabricantes | Semtech | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SC419 (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
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SC419
POWER MANAGEMENT
Features
Power system
• Input voltage — 3V to 28V
• Integrated bootstrap switch
• 1% reference tolerance -40 to +85 °C
• EcoSpeedTM architecture with pseudo-fixed fre-
quency adaptive on-time control
• Internal soft-start and soft-shutdown at output
• SmartDriveTM
Logic input/output control
• Independent control EN for LDO and switcher
• Programmable VIN UVLO threshold
• Power good output
• Selectable power save mode
• Programmable ultrasonic power save mode
Protections
• Over-voltage/under-voltage
• TC compensated RDS(ON) sensed current limit
• Thermal shutdown
• Smart power save
Output capacitor types
• High ESR — SP, POSCAP, OSCON
• Ceramic capacitors
Package — 3 x 3mm, 20-pin MLPQ
Lead-free and halogen free
RoHS and WEEE compliant
Applications
Office automation and computing
Networking and telecommunication equipment
Point-of-load power supplies and module replacement
EcoSpeedTM DC-DC Converter
with Integrated Boost Diode
Description
The SC419 is a synchronous buck power supply controller.
It features a bootstrap switch in a space-saving MLPQ-
3 x 3mm 20-pin package. The device is highly efficient
and uses minimal PCB area. It uses pseudo-fixed frequency
adaptive on-time operation to provide fast transient
response.
The SC419 supports using standard capacitor types such
as electrolytic or special polymer in addition to ceramic, at
switching frequencies up to 1MHz. The programmable
frequency, synchronous operation, and programmable
power-save provide high efficiency operation over a wide
load range.
Additional features include cycle-by-cycle current limit,
soft-start, under and over-voltage protection, program-
mable over-current protection, soft shutdown, selectable
power-save modes, and programmable ultra-sonic power-
save. The device also provides an enable input and a
power good output, useful for sequencing multiple
devices.
The input voltage can range from 3V to 28V. The wide
input voltage range and programmable frequency make
the device extremely flexible and easy to use in a broad
range of applications. Support is provided for single cell
or multi-cell battery systems in addition to traditional DC
power supply applications.
Typical Application Circuit
VIN
VIN
5V
PGOOD
ENABLE
RTON
5V
0.1µF
1µF
PSV
VIN
PGOOD
EN
TON
VDDA
VDDP
SC419
DH
LX
BST
ILIM RILIM
DL
VOUT
PSV
AGND
PGND
FB
VIN
L1
CIN
+ COUT
VOUT
July 27, 2010
© 2010 Semtech Corporation
1 page  
SC419
Electrical Characteristics (continued)
Parameter
Logic Inputs/Outputs
Logic Input High Voltage - EN
Logic Input High Voltage - PSV
Logic Input Low Voltage - EN
EN Input Bias Current
FB Input Bias Current
PSV Input Bias Current
High-Side Driver (DH, BST, LX)
Peak Current(1)
On Resistance
Rise Time(1)
Fall Time(1)
Propagation Delay(1)
Shoot-thru Protection Delay(1)
Bootstrap Switch On Resistance
Low-Side Driver (DL, VDDP, PGND)
Peak Current(1)
On Resistance
Rise Time(1)
Fall Time(1)
Notes:
(1) Guaranteed by design.
Conditions
Forced continuous mode (PSV pulled to VDDA);
PSV with respect to VDDA
With respect to VDDA
EN = VDDA or AGND
FB = VDDA or AGND
PSV = VDDA
R ,DH_PULL-UP LX < 0.5V
R ,DH_PULL-UP LX > 0.5V
RDH_PULL-DOWN
CDH-LX = 3nF
CDH-LX = 3nF
From FB Comparator Input to DH
RDL_PULL-UP
RDL_PULL-DOWN
CDL = 3nF
CDL = 3nF
Min Typ Max Units
1.0 V
-0.4 V
0.4 V
-10 +10 μA
-1 +1 μA
1 μA
2.0 A
3.0 6.0 Ω
1.0 2.0 Ω
0.6 1.2 Ω
22 ns
12 ns
30 45 60 ns
10 20 30 ns
10 Ω
4.0
1.3 2.1
0.50 0.86
7
3.5
A
Ω
Ω
ns
ns
5 Page 
SC419
Applications Information
General Description
The SC419 is a step down synchronous DC-DC buck con-
troller. It provides high efficiency operation in a space
saving 3 x 3 (mm) 20-pin package. The programmable
operating frequency range from 200kHz to 1MHz enables
optimizing the configuration for PCB area and efficiency.
The controller uses a pseudo-fixed frequency adaptive
on-time control. This allows fast transient response which
permits the use of smaller output capacitors.
Input Voltage Requirements
The SC419 requires three input supplies for normal opera-
tion: VIN, VDDA, and VDDP. VIN can operate over the wide
range of 3V to 28V. VDDA and VDDP require an external
5V supply. VDDA and VDDP should be connected to the
same source voltage.
Psuedo-fixed Frequency Adaptive On-time Control
The PWM control method used by the SC419 is pseudo-
fixed frequency, adaptive on-time, as shown in Figure 1.
The ripple voltage generated at the output capacitor ESR
is used as a PWM ramp signal. This ripple is used to trigger
the on-time of the controller.
VIN
Q1
VLX
Q2
TON
VLX
CIN
VFB FB Threshold
L
ESR
+
COUT
VOUT
FB
Figure 1 — PWM Control Method, VOUT Ripple
The adaptive on-time is determined by an internal one-
shot timer. When the one-shot is triggered by the output
ripple, the device sends a single on-time pulse to the high-
side MOSFET. The pulse period is determined by VOUT and
VIN. The period is proportional to output voltage and
inversely proportional to input voltage. With this adaptive
on-time configuration, the device automatically antici-
pates the on-time needed to regulate VOUT for the present
VIN condition and at the selected frequency.
The advantages of adaptive on-time control are:
• Predictable operating frequency compared to
• other variable frequency methods.
Reduced component count by eliminating the
• error amplifier and compensation components.
Reduced component count by removing the
• need to sense and control inductor current.
Fast transient response — the response time is
controlled by a fast comparator instead of a typi-
• cally slow error amplifier.
Reduced output capacitance due to fast tran-
sient response.
One-Shot Timer and Operating Frequency
One-shot timer operation is shown in Figure 2. The FB
comparator output goes high when VFB is less than the
internal 500mV reference. This feeds into the gate drive
and turns on the high-side MOSFET, and also starts the
one-shot timer. The one-shot timer uses an internal com-
parator and a capacitor. One comparator input is con-
nected to VOUT, the other input is connected to the
capacitor. When the on-time begins, the internal capaci-
tor charges from zero volts through a current which is
proportional to VIN. When the capacitor voltage reaches
VOUT, the on-time is completed and the high-side MOSFET
turns off.
FB FB
500mV
Comparator
-
+
Gate
Drives VIN
DH
Q1
VLX L
VOUT
VIN
One-Shot
Timer
ESR
DL
Q2
COUT
+
RTON On-time = K x RTON x (VOUT/VIN)
Figure 2 — On-Time Generation
VOUT
FB
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet SC419.PDF ] | |
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