Step-Down Converter. RT6236B Datasheet

RT6236B Converter. Datasheet pdf. Equivalent

RT6236B Datasheet
Recommendation RT6236B Datasheet
Part RT6236B
Description Synchronous Step-Down Converter
Feature RT6236B; ® RT6236A/B 6A, 18V, 650kHz, ACOTTM Synchronous Step-Down Converter General Description The RT6236.
Manufacture Richtek
Datasheet
Download RT6236B Datasheet




Richtek RT6236B
®
RT6236A/B
6A, 18V, 650kHz, ACOTTM Synchronous Step-Down Converter
General Description
The RT6236A/B is a high-performance 650kHz, 6A step-
down regulator with internal power switches and
synchronous rectifiers. It features quick transient response
using its Advanced Constant On-Time (ACOTTM) control
architecture that provides stable operation with small
ceramic output capacitors and without complicated
external compensation, among other benefits. The input
voltage range is from 4.5V to 18V and the output is
adjustable from 0.7V to 8V. The proprietary ACOTTM control
improves upon other fast response constant on-time
architectures, achieving nearly constant switching
frequency over line, load, and output voltage ranges. Since
there is no internal clock, response to transients is nearly
instantaneous and inductor current can ramp quickly to
maintain output regulation without large bulk output
capacitance. The RT6236A/B is stable with and optimized
for ceramic output capacitors. With internal 51mΩ switches
and 18mΩ synchronous rectifiers, the RT6236A/B displays
excellent efficiency and good behavior across a range of
applications, especially for low output voltages and low
duty cycles. Cycle-by-cycle current limit provides
protection against shorted outputs, input under-voltage
lock-out, externally-adjustable soft-start, output under- and
over-voltage protection, and thermal shutdown provide safe
and smooth operation in all operating conditions. The
RT6236A/B is available in the UQFN-13JL 2x3 (FC)
package, with exposed thermal pad.
Features
Fast Transient Response
Advanced Constant On-Time (ACOTTM) Control
4.5V to 18V Input Voltage Range
Adjustable Output Voltage from 0.7V to 8V
6A Output Current
51mΩ Internal High-Side N-MOSFET and 18mΩ
Internal Low-Side N-MOSFET
Steady 650kHz Switching Frequency
Up to 95% Efficiency
Optimized for All Ceramic Capacitors
Externally-Adjustable, Pre-biased Compatible Soft-
Start
Cycle-by-Cycle Current Limit
Input Under-Voltage Lockout
Output Over- and Under-Voltage Protection
Power Good Output
Externally-Adjustable, Pre-biased Compatible Soft-
Start
Thermal Shutdown
Applications
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
Simplified Application Circuit
VIN
CIN
VPVCC
RPG
Enable
CSS
RT6236A/B
VIN SW
BOOT
PGOOD
EN FB
SS PVCC
GND
L
CBOOT
CFF R1
COUT
VOUT
VPVCC
CPVCC
R2
Copyright ©2018 Richtek Technology Corporation. All rights reserved.
DS6236A/B-03 January 2018
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1



Richtek RT6236B
RT6236A/B
Ordering Information
RT6236A/B
Package Type
QUF : UQFN-13JL 2x3 (U-Type) (FC)
Lead Plating System
G : Green (Halogen Free and Pb Free)
H : Hiccup Mode UVP
L : Latched OVP & UVP
A : PSM
B : PWM
Note :
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.
Pin Configuration
(TOP VIEW)
13 12 11
GND 1
10 VIN
EN 2
9 VIN
FB 3
8 PGOOD
NC 4
7 NC
56
UQFN-13JL 2x3 (FC)
Marking Information
RT6236AHGQUF
0Z : Product Code
0ZW
W : Date Code
RT6236BHGQUF
0X : Product Code
0XW
W : Date Code
RT6236ALGQUF
0Y : Product Code
0YW
W : Date Code
RT6236BLGQUF
0W : Product Code
0WW
W : Date Code
Functional Pin Description
Pin No.
Pin Name
Pin Function
1, 13
GND
Ground.
2 EN Enable control input.
3 FB
Converter feedback input. Connect to output voltage feedback resistor divider.
4, 7 NC
No internal connection.
5 SS Soft-start control. A external capacitor should be connected to GND.
6
PVCC
5V power supply output. A capacitor (typical 1F) should be connected to GND.
8 PGOOD Open drain power good output.
9, 10
VIN
Power input and connected to high-side MOSFET drain.
Bootstrap. This capacitor is needed to drive the power switch's gate above the
11
BOOT
supply voltage. It is connected between SW and BOOT pins to form a floating
supply across the power switch driver. A 0.1F capacitor is recommended for use.
12 SW
Switch output.
Copyright ©2018 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS6236A/B-03 January 2018



Richtek RT6236B
Functional Block Diagram
PVCC
BOOT
VIN
Reg
VIBIAS
PVCC
VREF
Min.
Off
PVCC
UGATE
OC
Control
Driver
LGATE
UV & OV
GND SW
PVCC
SW
Ripple
Gen.
6µA
SS
FB
+
-
-
Comparator
0.9 VREF
FB
+
-
VIN Comparator
SW On-Time
EN
RT6236A/B
VIN
SW
GND
PGOOD
Detailed Description
The RT6236A/B is a high-performance 650kHz 6A step-
down regulators with internal power switches and
synchronous rectifiers. It features an Advanced Constant
On-Time (ACOTTM) control architecture that provides
stable operation with ceramic output capacitors without
complicated external compensation, among other benefits.
The ACOTTM control mode also provide fast transient
response, especially for low output voltages and low duty
cycles.
The input voltage range is from 4.5V to 18V and the output
is adjustable from 0.7V to 8V. The proprietary ACOTTM
control scheme improves upon other constant on-time
architectures, achieving nearly constant switching
frequency over line, load, and output voltage ranges. The
RT6236A/B are optimized for ceramic output capacitors.
Since there is no internal clock, response to transients is
nearly instantaneous and inductor current can ramp quickly
to maintain output regulation without large bulk output
capacitance.
Constant On-Time (COT) Control
The heart of any COT architecture is the on-time one shot.
Each on-time is a pre-determined fixedperiod that is
triggered by a feedback comparator. This robust
Copyright ©2018 Richtek Technology Corporation. All rights reserved.
DS6236A/B-03 January 2018
EN
arrangement has high noise immunity and is ideal for low
duty cycle applications. After the on-time one-shot period,
there is a minimum off-time period before any further
regulation decisions can be considered. This arrangement
avoids the need to make any decisions during the noisy
time periods just after switching events, when the
switching node (SW) rises or falls. Because there is no
fixed clock, the high-side switch can turn on almost
immediately after load transients and further switching
pulses can ramp the inductor current higher to meet load
requirements with minimal delays.
Traditional current mode or voltage mode control schemes
typically must monitor the feedback voltage, current
signals (also for current limit), and internal ramps and
compensation signals, to determine when to turn off the
high-side switch and turn on the synchronous rectifier.
Weighing these small signals in a switching environment
is difficult to do just after switching large currents, making
those architectures problematic at low duty cycles and in
less than ideal board layouts.
Because no switching decisions are made during noisy
time periods, COT architectures are preferable in low duty
cycle and noisy applications. However, traditional COT
is a registered trademark of Richtek Technology Corporation.
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