Step-Down Converter. RT8079 Datasheet

RT8079 Converter. Datasheet pdf. Equivalent


Richtek RT8079
®
RT8079
2.95V to 6V Input, 3A Output, 2MHz, Synchronous
Step-Down Converter
General Description
The RT8079 is a high efficiency step-down converter and
capable of delivering 3A output current over a wide input
voltage range from 2.95V to 6V.
The RT8079 provides accurate regulation for a variety of
loads with ±3% accuracy. For reducing inductor size, it
provides up to 2MHz switching frequency. The efficiency
is maximized through the integrated 45mΩ MOSFETs
and 550μA typical supply current.
Under voltage lockout voltage of the RT8079 is 2.7V, and
it also provides external setting by a resistor network on
the enable pin.
The RT8079 provides protections such as inductor current
limit under voltage lockout and thermal shutdown. The
over temperature threshold is 145°C.
The RT8079 is available in WQFN-16L 3x3 package.
Ordering Information
RT8079
Package Type
QW : WQFN-16L 3x3 (W-Type)
Note :
Lead Plating System
G : Green (Halogen Free and Pb Free)
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
Features
z Integrated 45mΩ MOSFETs
z Input Range : 2.95V to 6V
z Adjustable PWM Frequency : 300kHz to 2MHz
z Output Current : 3A
z 95% Efficiency
z Adjustable Soft-Start
z Power Good Indicator
z Enable Control
z Under Voltage Lockout
z Current Limit
z Thermal Shutdown
z 16-Lead WQFN Package
z RoHS Compliant and Halogen Free
Applications
z Low-Voltage, High-Density Power Systems
z Distributed Power Systems
z Point-of-Load Conversions
Marking Information
62=YM
DNN
62= : Product Code
YMDNN : Date Code
Simplified Application Circuit
RT8079
VIN VIN SW
EN
PGOOD
SS/TR
RT/SYNC
BOOT
FB
COMP
GND
AGND
VOUT
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8079-01 February 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1


RT8079 Datasheet
Recommendation RT8079 Datasheet
Part RT8079
Description Synchronous Step-Down Converter
Feature RT8079; ® RT8079 2.95V to 6V Input, 3A Output, 2MHz, Synchronous Step-Down Converter General Description T.
Manufacture Richtek
Datasheet
Download RT8079 Datasheet




Richtek RT8079
RT8079
Pin Configurations
(TOP VIEW)
16 15 14 13
VIN
VIN
GND
GND
1
2
3
4
GND
17
12 SW
11 SW
10 SW
9 SS/TR
5 678
WQFN-16L 3x3
Functional Pin Description
Pin No.
1, 2, 16
3, 4,
17 (Exposed Pad)
5
6
7
8
9
10 to 12
Pin Name
VIN
GND
AGND
FB
COMP
RT/SYNC
SS/TR
SW
13 BOOT
14 PGOOD
15 EN
Pin Function
Power Input.
Power Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
Analog Ground.
Feedback Input.
Compensation Node for Converter Stability.
Frequency Setting and External Synchronous. Clock input.
Soft-Start and Tracking.
Switch Node. Connect this pin to external L-C filter.
Bootstrap Supply for High Side Gate Driver. Connect a capacitor between the
BOOT and SW pin.
Output of Power Good Indicator.
Chip Enable. Externally pulled high to enable and pulled low to disable this
chip. It is internally pulled up to high when the pin is floating.
Function Block Diagram
VIN
EN
RT/SYNC
SS/TR
FB
Internal pull up
current
Over Temperature
Protection
Enable Comparator
EN Threshold
Shutdown
Control
Current
Sense
UVLO
Oscillator
Slope
Compensation
Soft-Start
VREF
PWM
Comparator
Control
Logic
Error
Amplifier
PGOOD Threshold
PGOOD Comparator
Driver
BOOT
SW
GND
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
PGOOD COMP AGND
GND
is a registered trademark of Richtek Technology Corporation.
DS8079-01 February 2013



Richtek RT8079
Operation
The RT8079 is a synchronous step-down DC/DC converter
with two integrated power MOSFETs. It can deliver up to
3A output current from a 2.95V to 6V input supply. The
RT8079's current mode architecture allows the transient
response to be optimized over a wider input voltage and
load range. Cycle-by-cycle current limit provides protection
against shorted outputs and soft-start eliminates input
current surge during start-up. The RT8079 is
synchronizable to an external clock with frequency ranging
from 300kHz to 2MHz. The RT8079 is available in
WQFN-16L 3x3 package.
High side MOSFET peak current is measured by internal
sensing resistor. The Current Signal is where Slope
Compensator works together with sensing voltage sensing
resistor. The error amplifier adjusts COMP voltage by
comparing the feedback signal (VFB) from the output
voltage with the internal 0.827V reference. When the load
current increases, it causes a drop in the feedback voltage
relative to the reference, the COMP voltage then rises to
allow higher inductor current to match the load current.
EN Comparator
The RT8079 is enable when EN pin is higher than 1.25V.
It is disable when EN pin lower than 1.18V. There is an
internal pull-high current source to charge the EN pin to
high when the EN pin is floating.
Oscillator (OSC)
The internal oscillator that provides switching frequency
from 300kHz to 2MHz. It is adjusted using an external
timing resistor. It also can be synchronized by an external
clock in the range between 300kHz and 2MHz from RT/
SYNC pin.
RT8079
PGOOD Comparator
When the feedback voltage (VFB) rises above 93% or falls
below 107% of reference voltage the PGOOD open drain
output will be high impedance. The PGOOD open drain
output will be internally pulled low when the feedback
voltage (VFB) falls below 88% or rises above 113% of
reference voltage.
Soft-Start (SS)
An internal current source (2.2μA) charges an external
capacitor to build the soft-start ramp voltage (VSS). The
VFB voltage will track the VSS during soft-start interval.
The Soft-Start setting capacitor (CSS) for the Soft-Start
time (TSS) can be easily calculated by the following
equation :
CSS
(nF) =
TSS
(ms)× 2.2 (μA)
0.827 (V)
Over Temperature Protection (OTP)
The RT8079 implement an internal over temperature
protection. When junction temperature is higher than
145°C, it will stop switching. Until the junction temperature
decreases below 125°C, the RT8079 will re-soft-start from
initial condition.
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8079-01 February 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3





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