®
RT6206B
5.5A, 18V, 650kHz, ACOTTM Synchronous Step-Down Converter
General Description
Features
The RT6206B is a synchronous step-down DC/DC converter
with Advanced Constant On-Time (ACOTTM) mode control.
It achieves high power density to deliver up to 5.5A output
current from a 4.5V to 18V input supply. The proprietary
ACOTTM mode offers an optimal transient response over a
wide range of loads and all kinds of ceramic capacitors,
which allows the device to adopt very low ESR output
capacitor for ensuring performance stabilization. In
addition, RT6206B keeps an excellent constant switching
frequency under line and load variation and the integrated
synchronous power switches with the ACOTTM mode
operation provides high efficiency in whole output current
load range. Cycle-by-cycle current limit provides an
accurate protection by a valley detection of low side
MOSFET and external soft-start setting eliminates input
current surge during startup. Protection functions include
thermal shutdown for RT6206B.
The RT6206B are available in the SOP-8 (Exposed Pad)
and WDFN-10L 3x3 packages.
ACOTTM Mode Enables Fast Transient Response
4.5V to 18V Input Voltage Range
5.5A Output Current
35mΩ
Ω Internal Low Site N-MOSFET
Advanced Constant On-Time Control
Support All Ceramic Capacitors
Up to 95% Efficiency
Discontinuous Operating Mode at Light Load
Adjustable Output Voltage from 0.765V to 8V
Adjustable Soft-Start
Cycle-by-Cycle Current Limit
Input Under-Voltage Lockout
Thermal Shutdown
RoHS Compliant and Halogen Free
Applications
Ordering Information
RT6206B
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
QW : WDFN-10L 3x3 (W-Type)
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
Note :
Richtek products are :
Lead Plating System
G : Green (Halogen Free and Pb Free)
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
UVP Trim Operation
H : Hiccup
Suitable for use in SnPb or Pb-free soldering processes.
Simplified Application Circuit
RT6206B
VIN
VIN
SW
VOUT
BOOT
Enable
Power Good
EN
PGOOD*
VREG5
FB
GND
SS
* : PGOOD pin for WDFN-10L 3x3 only.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS6206B-01 May 2015
is a registered trademark of Richtek Technology Corporation.
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1
RT6206B
Pin Configurations
Marking Information
(TOP VIEW)
EN
FB
2
VREG5
3
SS
4
GND
9
RT6206BHGSP
8
VIN
7
BOOT
6
SW
5
GND
RT6206BHGSP : Product Number
RT6206BH
GSPYMDNN
RT6206BHGQW
SOP-8 (Exposed Pad)
1
2
3
GND
EN
FB
VREG5
SS
PGOOD
4
5
11
10
9
8
7
6
YMDNN : Date Code
5J= : Product Code
5J=YM
DNN
VIN
VIN
BOOT
SW
SW
YMDNN : Date Code
WDFN-10L 3x3
Functional Pin Description
Pin No.
SOP-8
WDFN-10L 3x3
(Exposed Pad)
Pin Name
Pin Function
1
1
EN
Enable Control Input. A logic-high enables the converter; a
logic-low forces the IC into shutdown mode reducing the supply
current to less than 10A.
2
2
FB
Feedback Voltage Input. It is used to regulate the output of the
converter to a set value via an external resistive voltage divider.
The feedback threshold voltage is 0.765V typically.
3
3
VREG5
Internal Regulator Output. Connect a 1F capacitor to GND to
stabilize output voltage.
4
4
SS
Soft-Start Time Setting. Connect an external capacitor between this
pin and GND to set the soft- start time.
5, 9
11
GND
(Exposed Pad) (Exposed Pad)
6
6, 7
7
8
8
9, 10
--
5
Power Ground. The exposed pad must be soldered to a large
PCB and connected to GND for maximum power dissipation.
SW
Switch Node. Connect this pin to an external L-C filter.
BOOT
Bootstrap Supply for High Side Gate Driver. Connect a 0.1F
capacitor between the BOOT and SW pin.
VIN
Power Input. The input voltage range is from 4.5V to 18V. Must
bypass with a suitably large (10F x 2) ceramic capacitor.
PGOOD
Open Drain Power Good Indicator Output.
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DS6206B-01 May 2015
RT6206B
Function Block Diagram
BOOT
VREG5
POR &
Reg
EN
VBIAS
Min.
Off-Time
OC
UV & OV
VREG5
6µA
SS
VIN
FB
VREG5
VIN
VREF
Control
Driver
SW
GND
SW
ZC
Ripple
Gen.
FB
+
Comparator
Comparator
FB
-
0.9 x VREF
+
PGOOD*
On-Time
* : PGOOD pin for WDFN-10L 3x3 only.
Operation
The RT6206B is a synchronous step-down converter with
advanced constant on-time control mode. Using the
ACOTTM control mode can reduce the output capacitance
and provide fast transient response. It can minimize the
component size without additional external compensation
network.
UVLO Protection
To protect the chip from operating at insufficient supply
voltage, the UVLO is needed. When the input voltage of
VIN is lower than the UVLO falling threshold voltage, the
device will be latch-off.
Thermal Shutdown
Internal Regulator
The regulator provides 5V power to supply the internal
control circuit. Connecting a 1μF ceramic capacitor for
decoupling and stability is required.
Soft-Start
In order to prevent the converter output voltage from
overshooting during the startup period, the soft-start
function is necessary. The soft-start time is adjustable
and can be set by an external capacitor.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS6206B-01 May 2015
When the junction temperature exceeds the OTP
threshold value, the IC will shut down the switching
operation. Once the junction temperature cools down and
is lower than the OTP lower threshold, the converter will
automatically resume switching
Power Good (for WDFN-10L 3x3 only)
After soft-start in finished, the power good function will be
activated. When the FB is activated, the PGOOD will
become an open-drain output. If the FB is below, the
PGOOD pin will be pulled low.
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RT6206B
Absolute Maximum Ratings
(Note 1)
Supply Voltage, VIN ----------------------------------------------------------------------------------------------Switch Voltage, SW ----------------------------------------------------------------------------------------------< 10ns ---------------------------------------------------------------------------------------------------------------BOOT to SW -------------------------------------------------------------------------------------------------------EN ---------------------------------------------------------------------------------------------------------------------Other Pins -----------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------WDFN-10L 3x3 -----------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad), θJA --------------------------------------------------------------------------------------SOP-8 (Exposed Pad), θJC -------------------------------------------------------------------------------------WDFN-10L 3x3, θJA -----------------------------------------------------------------------------------------------WDFN-10L 3x3, θJC -----------------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------
Recommended Operating Conditions
−0.3V to 20V
−0.8V to (VIN + 0.3V)
−5V to 25V
−0.3V to 6V
−0.3V to 20V
−0.3V to 6V
2.041W
1.667W
49°C/W
15°C/W
60°C/W
7.5°C/W
150°C
260°C
−65°C to 150°C
(Note 3)
Supply Voltage, VIN ----------------------------------------------------------------------------------------------- 4.5V to 18V
Junction Temperature Range ------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 12V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Supply Current
Shutdown Current
ISHDN
VEN = 0V
--
1
10
A
Quiescent Current
IQ
VEN = 5V, VFB = 0.8V
--
1
1.3
mA
Logic-High
2
--
18
Logic-Low
--
--
0.4
Logic Threshold
EN Input Voltage
V
VFB Voltage
TA = 25C
0.757 0.765 0.773
TA = 40C to 85C
0.755
--
0.775
--
0.01
0.1
A
4.8
5.1
5.4
V
--
--
20
mV
Feedback Threshold Voltage
VFB
Feedback Input Current
IFB
VFB = 0.8V
VREG5
6V VIN 18V, 0 < IVREG5 5mA
V
VREG5 Output
VREG5 Output Voltage
Line Regulation
6V VIN 18V, IVREG5 = 5mA
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DS6206B-01 May 2015
RT6206B
Parameter
Symbol
Min
Typ
Max
Unit
0 IVREG5 5mA
--
--
100
mV
IVREG5
VIN = 6V, VREG5 = 4V, TA = 25C
--
70
--
mA
High-Side
RDS(ON)_H
(VBOOT VSW ) = 5.5V
--
80
--
Low-Side
RDS(ON)_L
--
35
--
5.8
6.9
8.4
--
150
--
--
20
--
Load Regulation
Output Current
Test Conditions
RDS(ON)
Switch On
Resistance
m
Current Limit
Current Limit
ILIM
A
Thermal Shutdown
Thermal Shutdown Threshold
TSD
Shutdown Temperature
Thermal Shutdown Hysteresis TSD
C
On-Time Timer Control
On-Time
tON
VOUT = 1.05V
--
135
--
ns
Minimum Off-Time
tOFF(MIN)
VFB = 0.7V
--
260
310
ns
SS Charge Current
VSS = 0V
--
6
--
A
SS Discharge Current
VSS = 0.5V
0.1
0.2
--
mA
Wake Up VREG5
3.6
3.85
4.1
0.16
0.35
0.47
115
120
125
%
OVP Prop Delay
--
5
--
s
UVP Trip Threshold
65
70
75
UVP Hysteresis
--
10
--
UVP Prop Delay
--
250
--
s
Relative to Soft-Start Time
--
tSS
x 1.7
--
ms
VFB Rising
85
90
95
VFB Falling
--
85
--
2.5
5
--
Soft-Start
UVLO
UVLO Threshold
Hysteresis
V
Output Under Voltage and Over Voltage Protection
OVP Trip Threshold
UVP Enable Delay
OVP Detect
tUVPEN
%
Power Good
PGOOD Threshold
PGOOD Sink Current
PGOOD = 0.5V
%
mA
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS6206B-01 May 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
RT6206B
Typical Application Circuit
L1
1.4µH
RT6206B
VIN
C1
10µF x 2
C2
0.1µF
Input Signal
Power Good
VIN
SW
BOOT
EN
FB
PGOOD*
SS
R3
100k
C4
1µF
C6
0.1µF
C5
3.3nF
VOUT
1.05V/5.5A
C3
C7
22µF x 2
R1
8.25k
R2
22k
VREG5
GND
* : PGOOD pin for WDFN-10L 3x3 only.
Table 1. Suggested Component Values (VIN = 12V)
VOUT (V)
R1 (k)
R2 (k)
C3 (pF)
L1 (H)
C7 (F)
1
6.81
22.1
--
1.4
22 to 68
1.05
8.25
22.1
--
1.4
22 to 68
1.2
12.7
22.1
--
1.4
22 to 68
1.8
30.1
22.1
5 to 22
2
22 to 68
2.5
49.9
22.1
5 to 22
2
22 to 68
3.3
73.2
22.1
5 to 22
2
22 to 68
5
124
22.1
5 to 22
3.3
22 to 68
7
180
22.1
5 to 22
3.3
22 to 68
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RT6206B
Typical Operating Characteristics
Efficiency vs. Output Current
Output Voltage vs. Output Current
1.10
100
VOUT = 5V
90
1.09
1.08
Output Voltage (V)
Efficiency (%)
80
70
60
VOUT = 1.05V
50
40
30
1.07
1.06
1.05
1.04
1.03
1.02
20
10
1.01
VIN = 12V
0
0.001
0.01
0.1
1
VIN = 12V, VOUT = 1.05V, IOUT = 0A to 5.5A
1.00
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
10
Output Current (A)
Output Current (A)
Switching Frequency vs. Temperature
700
700
680
Switching Frequency (kHz)1
Switching Frequency (kHz)1
Switching Frequency vs. Output Current
800
600
500
400
300
200
100
VIN = 12V, VOUT = 1.05V, IOUT = 0A to 5.5A
0
660
640
620
600
580
560
540
520
500
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
-50
-25
0
Output current (A)
0.775
0.790
0.765
0.760
0.755
0.750
0.745
VIN = 12V, VOUT = 0.765V, IOUT = 0.6A
0.740
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18
Input Voltage (V)
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DS6206B-01 May 2015
50
75
100
125
Feedback Voltage vs. Temperature
0.800
Feedback Voltage (V)
Feedback Voltage (V)
Feedback Voltage vs. Input Voltage
0.780
0.770
25
Temperature (°C)
0.780
0.770
0.760
0.750
0.740
0.730
0.720
0.710
VIN = 12V, VOUT = 0.765V, IOUT = 0.6A
0.700
-50
-25
0
25
50
75
100
125
Temperature (°C)
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RT6206B
Shutdown Current vs. Temperature
Quiescent Current vs. Temperature
1000
VIN = 12V, VOUT = 1.05V, IOUT = 0A
VIN = 12V, VOUT = 1.05V, IOUT = 0A
950
25
Quiescent Current (μA)
Shutdown Current (μA)1
30
20
15
10
5
900
850
800
750
700
650
0
600
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
Temperature (°C)
Temperature (°C)
Current Limit vs. Input Voltage
Output Ripple Voltage
100
125
9.0
Current Limit (A)
8.5
VOUT
(10mV/Div)
8.0
7.5
7.0
6.5
VSW
(5V/Div)
6.0
5.5
VIN = 12V, VOUT = 1.05V, IOUT = 5A
5.0
4
6
8
10
12
14
16
Time (500ns/Div)
18
Input Voltage (V)
Load Transient Response
VIN
(10V/Div)
VOUT
(20mV/Div)
VOUT
(0.5V/Div)
IOUT
(2A/Div)
VIN = 12V, VOUT = 1.05V, IOUT = 1A to 5A
Time (100μs/Div)
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Power On from VIN
IOUT
(5A/Div)
VIN = 12V, VOUT = 1.05V, IOUT = 5A
Time (2.5ms/Div)
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RT6206B
Power Off from VIN
Power On from EN
VIN
(10V/Div)
VEN
(5V/Div)
VOUT
(0.5V/Div)
VOUT
(0.5V/Div)
IOUT
(5A/Div)
IOUT
(5A/Div)
VIN = 12V, VOUT = 1.05V, IOUT = 5A
VIN = 12V, VOUT = 1.05V, IOUT = 5A
Time (10ms/Div)
Time (500μs/Div)
EN Threshold Voltage vs. Temperature
Power Off from EN
EN Threshold Voltage (V)
1.4
VEN
(5V/Div)
VOUT
(0.5V/Div)
IOUT
(5A/Div)
1.3
Rising
1.2
1.1
1.0
0.9
Falling
0.8
0.7
0.6
VIN = 12V, VOUT = 1.05V, IOUT = 5A
Time (50μs/Div)
VIN = 12V, VOUT = 1.05V
0.5
-50
-25
0
25
50
75
100
125
Temperature (°C)
UVLO vs. Temperature
4.0
UVLO Voltage (V)
3.9
Rising
3.8
3.7
3.6
Falling
3.5
3.4
-50
-25
0
25
50
75
100
125
Temperature (°C)
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS6206B-01 May 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
9
RT6206B
Application Information
The RT6206B is a synchronous high voltage Buck converter
that can support the input voltage range from 4.5V to 18V
and the output current up to 5.5A. It adopts ACOTTM mode
control to provide a very fast transient response with few
external compensation components.
on the device again. For external timing control, the EN
pin can also be externally pulled high by adding a REN
resistor and CEN capacitor from the VIN pin (see Figure 1).
EN
VIN
PWM Operation
It is suitable for low external component count
configuration with appropriate amount of Equivalent Series
Resistance (ESR) capacitors at the output. The output
ripple valley voltage is monitored at a feedback point
voltage. The synchronous high side MOSFET is turned
on at the beginning of each cycle. After the internal
on-time expires, the MOSFET is turned off. The pulse
width of this on-time is determined by the converter's input
and output voltages to keep the frequency fairly constant
over the entire input voltage range.
Advanced Constant On-Time Control
The RT6206B has a unique circuit which sets the on-time
by monitoring the input voltage and SW signal. The circuit
ensures the switching frequency operating at 700kHz over
input voltage range and loading range.
EN
RT6206B
CEN
GND
Figure 1. External Timing Control
An external MOSFET can be added to implement digital
control on the EN pin when no system voltage above 2V
is available, as shown in Figure 2. In this case, a 100kΩ
pull-up resistor, REN, is connected between the VIN and
EN pins. MOSFET Q1 will be under logic control to pull
down the EN pin.
VIN
REN
100k
EN
Q1
EN
RT6206B
GND
Figure 2. Digital Enable Control Circuit
Soft-Start
The RT6206B contains an external soft-start clamp that
gradually raises the output voltage. The soft-start timing
can be programmed by the external capacitor between
the SS and GND pins. The chip provides a 6μA charge
current for the external capacitor. If a 3.9nF capacitor is
used, the soft-start will be 0.87ms (typ.). The available
capacitance range is from 2.7nF to 220nF.
t SS (ms) =
REN
C5 (nF) 1.365
ISS ( A)
Chip Enable Operation
The EN pin is the chip enable input. Pulling the EN pin
low (
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