sic417 Vishay, sic417 Datasheet - Page 7

• Manufacturer Part Number: sic417
• Description: 10-a, 28-v Integrated Buck Regulator With Programmable Ldo
• Manufacturer: Vishay

ELECTRICAL CHARACTERISTICS
APPLICATIONS INFORMATION
SiC417 Synchronous Buck Converter
The SiC417 is a step down synchronous buck dc-to-dc
converter with integrated power FETs and programmable
LDO. The SiC417 is capable of 10 A operation at very high
efficiency in a tiny 5 mm x 5 mm - 32 pin package. The
programmable operating frequency range of 200 kHz to
1 MHz, enables the user to optimize the solution for minimum
board space and optimum efficiency.
The buck controller employs pseudo-fixed frequency
adaptive on-time control. This control scheme allows fast
transient response thereby lowering the size of the power
components used in the system.
Input Voltage Range
The SiC417 requires two input supplies for normal operation:
V
28 V. V5V requires a 5 V supply input that can be an external
source or the internal LDO configured to supply 5 V.
Pseudo-Fixed Frequency Adaptive On-Time Control
The PWM control method used for the SiC417 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.
The adaptive on-time is determined by an internal oneshot
timer. When the one-shot is triggered by the output ripple, the
device sends a single on-time pulse to the highside
MOSFET. The pulse period is determined by V
the period is proportional to output voltage and inversely
proportional to input voltage. With this adaptive on-time
arrangement, the device automatically anticipates the
on-time needed to regulate V
condition and at the selected frequency.
Document Number: 69062
S09-0799-Rev. B, 11-May-09
IN
and V5V. V
Over Current Protection: V
IN
operates over the wide range from 3 V to
IN
OUT
= 12 V, V
for the present V
OUT
= 1.2 V
OUT
and V
New Product
IN
IN
;
The adaptive on-time control has significant advantages over
traditional control methods used in the controllers today.
• Reduced component count by eliminating DCR sense or
• Reduced
• Ultra fast transient response because of fast loop,
• Predictable frequency spread because of constant on-time
• Fast transient response enables operation with minimum
Overall, superior performance compared to fixed frequency
architectures.
Q2
Q1
current sense resistor as no need of a sensing inductor
current.
compensation by eliminating the no error amplifier and
other components.
absence of error amplifier speeds up the transient
response.
architecture.
output capacitance
V
IN
Figure 1 - Output Ripple and PWM Control Method
V
Ultra-Sonic Power-Save at I
LX
Saves
C
IN
L
external
t
ON
+
ESR
V
FB
C
components
OUT
Vishay Siliconix
V
LX
OUT
= 0 A
FB threshold
www.vishay.com
SiC417
used
FB
V
OUT
for
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