®
RT8298E
6A, 24V, 600kHz Step-Down Converter with Synchronous
Gate Driver
General Description
The RT8298E is a synchronous step-down DC/DC converter
with an integrated high side internal power MOSFET and
a gate driver for a low side external power MOSFET. It
can deliver up to 6A output current from a 4.5V to 24V
input supply. The RT8298E'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
RT8298E is synchronizable to an external clock with
frequency ranging from 300kHz to 1.5MHz.
The RT8298E is available in WDFN-14L 4x3 and SOP-8
(Exposed Pad) packages.
Features
4.5V to 24V Input Voltage Range
6A Output Current
45mΩ Internal High Side N-MOSFET
Ω
Current Mode Control
600kHz Switching Frequency
Adjustable Output from 0.8V to 15V
Up to 95% Efficiency
Internal Compensation
Stable with Ceramic Capacitors
Synchronous External Clock : 300kHz to 1.5MHz
Cycle-by-Cycle Current Limit
Input Under Voltage Lockout
Output Under Voltage Protection
Power Good Indicator
Thermal Shutdown Protection
RoHS Compliant and Halogen Free
Applications
Point of Load Regulator in Distributed Power System
Digital Set top Boxes
Personal Digital Recorders
Broadband Communications
Flat Panel TVs and Monitors
Simplified Application Circuit
V
IN
C
IN
VIN
RT8298E
BOOT
C
BOOT
SW
L
V
OUT
Q1
R1
C
OUT
R2
VCC
C
VCC
Power Good
Enable
PGOOD
EN/SYNC
BG
FB
GND
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8298E-02
October 2015
www.richtek.com
1
RT8298E
Ordering Information
RT8298E
Package Type
QW : WDFN-14L 4x3 (W-Type)
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Note :
Richtek products are :
½
Marking Information
RT8298EZQW
00 : Product Code
YMDNN : Date Code
00 YM
DNN
RT8298EZSP
RT8298EZSP : Product Number
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.
RT8298E
ZSPYMDNN
YMDNN : Date Code
½
Pin Configurations
(TOP VIEW)
FB
PGOOD
EN/SYNC
VIN
VIN
VIN
NC
1
2
3
4
5
6
7
14
13
12
GND
15
11
10
9
8
GND
BG
VCC
BOOT
SW
SW
SW
SW
BOOT
VCC
BG
2
3
4
8
VIN
EN/SYNC
FB
GND
GND
9
7
6
5
WDFN-14L 4x3
SOP-8 (Exposed Pad)
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8298E-02
October 2015
RT8298E
Functional Pin Description
Pin No.
WDFN-14L 4x3
SOP-8
(Exposed Pad)
6
Pin Name
Pin Function
Feedback Input. This pin is connected to the converter output. It
is used to set the output of the converter to regulate to the
desired value via an external resistive divider. The feedback
reference voltage is 0.808V typically.
Power Good Indicator with Open Drain (for RT8298EZQW only).
100k pull-high resistor is needed. The output of this pin is
pulled to low when the FB is lower than 0.75V; otherwise, it is
high impedance.
Enable or External Frequency Synchronization Input. A
logic-high (2V < EN < 5.5V) enables the converter; a logic-low
forces the IC into shutdown mode reducing the supply current to
less than 3A. For external frequency synchronization operation,
the available frequency range is from 300kHz to 1.5MHz.
Power Input. The available input voltage range is from 4.5V to
24V. A 22F or larger input capacitor is needed to reduce
voltage spikes at the input.
No Internal Connection.
Switching Node. Output of the internal high side MOSFET.
Connect this pin to external low-side N-MOSFET, inductor and
bootstrap capacitor.
Bootstrap for High Side Gate Driver. Connect a 1F ceramic
capacitor between the BOOT and SW pins
BG Driver Bias Supply. Decouple with a 1F X5R/X7R ceramic
capacitor between the VCC pin and GND.
Gate Driver Output. Connect this pin to the Gate of the external
low-side N-MOSFET.
Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum thermal dissipation.
1
FB
2
--
PGOOD
3
7
EN/SYNC
4, 5, 6
7
8, 9, 10
8
--
1
VIN
NC
SW
11
12
13
2
3
4
BOOT
VCC
BG
14,
5,
GND
15 (Exposed Pad) 9 (Exposed Pad)
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8298E-02
October 2015
www.richtek.com
3
RT8298E
Function Block Diagram
VIN
VCC
Internal
Regulator
Enable
Comparator
+
1.7V
-
5k
3V
V
CC
Slope
Current Sense
Compensator Amplifier
+
-
V
CC
OTP
BOOT
UV Comparator
V
CC
6nA
V
SS
15pF
FB
0.808V
54pF
+
+
EA
-
OSC
R
SENSE
EN/SYNC
Foldback
Control
0.4V
+
-
Switch
Controller
Current
Signal
COMP
+
-
45m
SW
Current
Comparator
BG
Driver
BG
300k
1pF
PGOOD
Comparator
0.75V
+
-
PGOOD
GND
Operation
The RT8298E is a synchronous high voltage Buck
Converter that can support the input voltage range from
4.5V to 24V and the output current can be up to 6A. The
RT8298E uses a constant frequency, current mode
architecture. In normal operation, the high side N-MOSFET
is turned on when the Switch Controller is set by the
oscillator (OSC) and is turned off when the current
comparator resets the Switch Controller. While the N-
MOSFET is turned off, the external low side N-MOSFET
is turned on by BG Driver with 5V driving voltage from
Internal Regulator (V
CC
) until next cycle begins.
Error Amplifier
The error amplifier EA adjusts COMP voltage by comparing
the feedback signal (V
FB
) from the output voltage with the
internal 0.808V 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.
UV Comparator
If the feedback voltage (V
FB
) is lower than threshold voltage
0.4V, the UV Comparator's output will go high and the
Switch Controller will turn off the high side MOSFET. The
output under voltage protection is designed to operate in
Hiccup mode.
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
Oscillator (OSC)
The internal oscillator runs at nominal frequency 600kHz
and can be synchronized by an external clock in the range
between 300kHz and 1.5MHz from EN/SYNC pin.
PGOOD Comparator
This function is available for RT8298EZQW only. When
the feedback voltage (V
FB
) is higher than threshold voltage
0.75V, the PGOOD open drain output will be high
impedance.
Enable Comparator
Internal 5kΩ resistor and Zener diode are used to clamp
the input signal to 3V. A 1.7V reference voltage is for EN
logic-high threshold voltage. The EN pin can be connected
to VIN through a 100kΩ resistor for automatic startup.
Foldback Control
When V
FB
is lower than 0.7V, the oscillation frequency
will be proportional to the feedback voltage.
Soft-Start (SS)
An internal current source (6nA) charges an internal
capacitor (15pF) to build the soft-start ramp voltage (V
SS
).
The V
FB
voltage will track the internal ramp voltage during
soft-start interval. The typical soft-start time is 2ms.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8298E-02
October 2015
RT8298E
Absolute Maximum Ratings
(Note 1)
−0.3V
to 26V
−0.3V
to (V
IN
+ 0.3V)
−5V
to 30V
−0.3V
to 6V
−0.3V
to 6V
1.667W
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------
Switching Voltage, SW --------------------------------------------------------------------------------------------
SW (AC) < 20ns -----------------------------------------------------------------------------------------------------
BOOT to SW ---------------------------------------------------------------------------------------------------------
Other Pins -------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
WDFN-14L 4x3 -------------------------------------------------------------------------------------------------------
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------- 1.333W
Package Thermal Resistance (Note 2)
WDFN-14L 4x3,
θ
JA
------------------------------------------------------------------------------------------------- 60°C/W
WDFN-14L 4x3,
θ
JC
------------------------------------------------------------------------------------------------- 7.5°C/W
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------------- 75°C/W
SOP-8 (Exposed Pad),
θ
JC
--------------------------------------------------------------------------------------- 15°C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C
Junction Temperature ----------------------------------------------------------------------------------------------- 150°C
Storage Temperature Range --------------------------------------------------------------------------------------
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------- 200V
(Note 4)
Recommended Operating Conditions
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 4.5V to 24V
Junction Temperature Range --------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 12V, T
A
= 25°C, unless otherwise specified)
Parameter
Shutdown Supply Current
Supply Current
Feedback Reference Voltage
Feedback Current
High-Side Switch On Resistance
High-Side Switch Current Limit
Oscillation Frequency
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On-Time
Input Under Voltage Lockout Threshold
Input Under Voltage Lockout Threshold
Hysteresis
Symbol
Test Conditions
V
EN
= 0V
V
EN
= 3V, V
FB
= 1V
Min
--
--
--
--
--
--
--
--
--
4
--
Typ
1
0.9
10
45
10
600
190
90
100
4.2
400
Max
--
--
0.82
--
--
--
--
--
--
--
4.4
--
Unit
A
mA
V
nA
m
A
kHz
kHz
%
ns
V
mV
V
REF
I
FB
R
DS(ON)
4.5V
V
IN
24V
V
FB
= 0.8V
BOOT
SW = 4.8V
0.796 0.808
f
OSC1
f
OSC2
D
MAX
t
ON
V
UVLO
V
UVLO
V
FB
= 0V
V
FB
= 0.6V
V
FB
= 1V
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8298E-02
October 2015
www.richtek.com
5
FPGA/CPLD
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
