RT9618/A
Synchronous-Rectified Buck MOSFET Drivers
General Description
The RT9618/A is a high frequency, dual MOSFET driver
specifically designed to drive two power N-Channel
MOSFETs in a synchronous-rectified buck converter
topology. This driver combined with Richtek’ s series of
Multi-Phase Buck PWM controller form a complete core-
voltage regulator solution for advanced micro-processors.
The RT9618/A drives both the lower/upper gate in a
synchronous-rectifier bridge with 12V. This drive-voltage
flexibility provides the advantage of optimizing applications
involving trade-offs between switching losses and
conduction losses.
RT9618A has longer UGATE/LGATE deadtime which can
drive the MOSFETs with large gate RC value, avoiding the
shoot-through phenomenon. RT9618 is targeted to drive
low gate RC MOSFETs and performs better efficiency.
The output drivers in the RT9618/A can efficiently switch
power MOSFETs at frequency up to 500kHz. Switching
frequency above 500kHz has to take into account the
thermal dissipation of SOP-8 package. RT9618/A is
capable to drive a 3nF load with a 30ns rise time. RT9618/
A implements bootstrapping on the upper gate with an
external capacitor and
an embedded diode.
This reduces
implementation complexity and allows the use of higher
performance, cost effective N-Channel MOSFETs. Adaptive
shoot-through protection is integrated to prevent both
MOSFETs from conducting simultaneously.
Features
Drives Two N-Channel MOSFETs
Adaptive Shoot-Through Protection
Embedded Boot Strapped Diode
Support High Switching Frequency
Fast Output Rise Time
Small SOP-8 Package
Tri-State Input for Bridge Shutdown
Supply Under Voltage Protection
Upper MOSFET Direct Shorted Protection
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Core Voltage Supplies for Desktop, Motherboard CPU
High Frequency Low Profile DC-DC Converters
High Current Low Voltage DC-DC Converters
Ordering Information
RT9618/A
Package Type
S : SOP-8
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Long Dead Time
Short Dead Time
Note :
RichTek Pb-free and Green 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.
100% matte tin (Sn) plating.
Pin Configurations
(TOP VIEW)
BOOT
PWM
OD
VCC
2
3
4
8
7
6
5
UGATE
PHASE
PGND
LGATE
SOP-8
DS9618/A-04 March 2007
www.richtek.com
1
RT9618/A
Typical Application Circuit
ATX_12V
C8
10uF
C9
10uF
L1
2.2uH
V
IN
C10
1000uF
C11
1000uF
C12
1000uF
C13
10uF
C2
1uF
C14
10uF
D1
R2
1
1
BOOT
ATX_12V
R1
10
C1
1uF
+5V
PWM
4 VCC
UGATE
8
R3
2.2
Q1
L2
1uH
+
+
+
RT9618/A
3
2
OD
PWM
PHASE
LGATE
PGND
6
7
5
R4
0
R5
2.2
Q2
V
CORE
+
C3
3.3nF
C4
2200uF
C5
2200uF
C6
10uF
C7
10uF
Functional Pin Description
Pin No.
1
2
3
4
5
6
7
8
Pin Name
BOOT
PWM
OD
VCC
LGATE
PGND
PHASE
UGATE
Pin Function
Floating bootstrap supply pin for upper gate drive.
Input PWM signal for controlling the driver.
Output Disable. When low, both UGATE and LGATE are driven low and the normal
operation is disabled.
+12V Supply Voltage.
Lower Gate Drive Output. Connected to gate of low-side power N-Channel MOSFET.
Common Ground.
Connected this pin to the source of the high-side MOSFET and the drain of the low-side
MOSFET.
Upper Gate Drive Output. Connected to gate of high-side power N-Channel MOSFET.
www.richtek.com
2
DS9618/A-04 March 2007
RT9618/A
Function Block Diagram
VCC
Internal
5V
POR
R
PWM
R
Turn Off Detect
OD
Shoot-Through
Protection
PHASE
Input
Disable
Shoot-Through
Protection
BOOT
UGATE
VCC
LGATE
PGND
Timing Diagram
PWM
LGATE
t
pdlLGATE
90%
2V
t
pdlUGATE
2V
90%
2V
UGATE
t
pdhUGATE
t
pdhLGATE
2V
DS9618/A-04 March 2007
www.richtek.com
3
RT9618/A
Absolute Maximum Ratings
(Note 1)
−0.3V
to 15V
−0.3V
to 15V
−0.3V
to V
CC
+ 15V
−0.3V
to 42V
−5V
to 15V
Supply Voltage, V
CC
-------------------------------------------------------------------------------------
BOOT to PHASE -----------------------------------------------------------------------------------------
BOOT to GND
DC ------------------------------------------------------------------------------------------------------------
< 200ns -----------------------------------------------------------------------------------------------------
PHASE to GND
DC ------------------------------------------------------------------------------------------------------------
< 200ns -----------------------------------------------------------------------------------------------------
−10V
to 30V
LGATE
DC ------------------------------------------------------------------------------------------------------------ GND
−
0.3V to V
CC
+ 0.3V
< 200ns -----------------------------------------------------------------------------------------------------
−2V
to V
CC
+ 0.3V
UGATE ------------------------------------------------------------------------------------------------------ V
PHASE
−
0.3V to V
BOOT
+ 0.3V
< 200ns ----------------------------------------------------------------------------------------------------- V
PHASE
−
2V to V
BOOT
+ 0.3V
PWM Input Voltage -------------------------------------------------------------------------------------- GND
−
0.3V to 7V
OD ------------------------------------------------------------------------------------------------------------ GND
−
0.3V to 7V
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 -------------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 4)
SOP-8,
θ
JA
-------------------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------
Storage Temperature Range ---------------------------------------------------------------------------
ESD Susceptibility (Note 2)
HBM (Human Body Mode) -----------------------------------------------------------------------------
MM (Machine Mode) -------------------------------------------------------------------------------------
0.625W
160°C/W
260°C
−
40°C to 150°C
2kV
200V
Recommended Operating Conditions
(Note 3)
Supply Voltage, V
CC
------------------------------------------------------------------------------------- 12V
±10%
Junction Temperature Range --------------------------------------------------------------------------- 0°C to 125°C
Ambient Temperature Range --------------------------------------------------------------------------- 0°C to 70°C
Electrical Characteristics
(Recommended Operating Conditions, T
A
= 25°C unless otherwise specified)
Parameter
V
CC
Supply Voltage
Power Supply Voltage
V
CC
Supply Current
Power Supply Current
Power-On Reset
POR Threshold
Hysteresis
Symbol
Test Conditions
Min
Typ
Max
Units
V
CC
I
VCC
V
BOOT
= 12V, PWM = 0V
7.3
--
13.5
V
--
1
2.5
mA
V
VCCrth
V
VCChys
V
CC
Rising
5.5
--
6.4
2.2
7.3
--
V
V
To be continued
www.richtek.com
4
DS9618/A-04 March 2007
RT9618/A
Parameter
PWM Input
Maximum Input Current
PWM Floating Voltage
PWM Rising Threshold
PWM Falling Threshold
Output Disable Input
OD Rising Threshold
OD Hysteresis
Timing
UGATE Rise Time
UGATE Fall Time
LGATE Rise Time
LGATE Fall Time
RT9618
RT9618A
Propagation Delay
t
rUGATE
t
fUGATE
t
rLGATE
t
fLGATE
t
pdhUGATE
t
pdlUGATE
RT9618/A t
pdhLGATE
t
pdlLGATE
Output
UGATE Drive Source
UGATE Drive Sink
LGATE Drive Source
LGATE Drive Sink
R
UGATEsr
R
UGATEsk
R
LGATEsr
R
LGATEsk
V
BOOT
−
V
PHASE
= 12V
V
BOOT
−
V
PHASE
= 12V
V
CC
= 12V
V
CC
= 12V
--
--
--
--
1.9
1.4
1.9
1.1
3
3
3
2.2
Ω
Ω
Ω
Ω
See Timing Diagram
V
CC
= 12V, 3nF load
V
CC
= 12V, 3nF load
V
CC
= 12V, 3nF load
V
CC
= 12V, 3nF load
V
BOOT
−
V
PHASE
= 12V
See Timing Diagram
--
--
--
--
--
--
--
--
--
27
32
35
27
20
90
15
20
8
35
45
45
38
--
--
--
--
--
ns
ns
ns
ns
ns
V
ODrth
V
ODhys
1.5
--
1.8
0.5
2.1
--
V
V
I
PWM
V
PWMfl
V
PWMrth
V
PWMfth
PWM = 0V or 5V
V
CC
= 12V
--
--
3.2
1.1
300
2.4
3.6
1.3
--
--
3.9
1.5
μA
V
V
V
Symbol
Test Conditions
Min
Typ
Max
Units
Note 1.
Stresses listed as the above
“Absolute
Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. 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 for extended periods may
remain possibility to affect device reliability.
Note 2.
Devices are ESD sensitive. Handling precaution recommended.
Note 3.
The device is not guaranteed to function outside its operating conditions.
Note 4.
θ
JA
is measured in the natural convection at T
A
= 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
DS9618/A-04 March 2007
www.richtek.com
5
京公网安备 11010802033920号
EEWORLD
