Preliminary
RT8101/A
12V Synchronous Buck PWM DC-DC
General Description
The RT8101/A are DC/DC synchronous buck PWM
controllers with embedded driver support up to 12V+12V
boot-strapped voltage for high efficiency power driving. The
parts are with full functions of voltage regulation, power
monitoring and protection into a single small footprint
packages SOP-8 and SOP-8 (Exposed Pad).
The RT8101/A apply a high-gain voltage mode PWM control
for simple application design. An internal 0.8V reference
allows the output voltage to be precisely regulated to low
voltage requirement. The parts are proposed with two type
including RT8101 and RT8101A with fixed operating
frequency of 300kHz and 600kHz respectively. Based on
the features that RT8101/A offered, the parts provide an
optimum solution between efficiency, total B.O.M. count,
and cost.
Features
Single 12V Bias Supply
Drives All Low Cost N-MOSFETs
High-Gain Voltage Model PWM Control
300kHz/600kHz Fixed Frequency Oscillator
Fast Transient Response :
High-Speed GM Amplifier
Full 0 to 100% Duty Ratio
External Compensation in the Control Loop
Internal Soft-Start
Adaptive Non-Overlapping Gate Driver
Over-Current Fault Monitor on MOSFET, No
Current Sense Resistor Required
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Graphic Card
Motherboard, Desktop Servers
IA Equipments
Telecomm Equipments
High Power DC-DC Regulators
Ordering Information
RT8101/A
Package Type
S : SOP-8
SP : SOP-8 (Exposed Pad)
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
600kHz
300kHz
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
UGATE
GND
LGATE
2
3
4
8
7
6
5
PHASE
COMP
FB
VCC
SOP-8
BOOT
UGATE
GND
LGATE
2
3
4
GND
8
7
6
5
PHASE
COMP
FB
VCC
SOP-8(Exposed Pad)
DS8101/A-01 March 2007
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1
RT8101/A
Typical Application Circuit
12V
Preliminary
R
BOOT
V
IN
(+3.3V/+5V/+12V)
RT8101/A
1
5
6
3
BOOT
VCC
FB
GND
UGATE
PHASE
LGATE
COMP
2
8
4
7
C
PSC
Q2
R
UGATE
Q1
C
IN
L
OUT
V
OUT
R
C
OUT
Functional Pin Description
BOOT (Pin 1)
Bootstrap supply for the upper gate driver. Connect the
bootstrap capacitor between BOOT pin and the PHASE
pin. The bootstrap capacitor provides the charge to turn
on the upper MOSFET.
UGATE (Pin 2)
Upper gate driver output. Connect to gate of the high-
side power N-Channel MOSFET. This pin is monitored by
the adaptive shoot-through protection circuitry to
determine when the upper MOSFET
is turned off.
GND (Pin 3)
Signal ground for the IC.
LGATE (Pin 4)
Lower gate driver output. Connect to the gate of the low-
side power N-Channel MOSFET. This pin is monitored by
the adaptive shoot-through protection
circuitry to determine
when the lower MOSFET is turned off.
VCC (Pin 5)
Connect this pin to a well-decoupled 12V bias supply. It
is also the positive supply for the lower gate driver, LGATE.
FB (Pin 6)
Buck converter feedback voltage. This pin is the inverting
input of the error amplifier. FB senses the switcher output
through an external resistor divider network.
COMP (Pin 7)
Buck converter external compensation. This pin is used
to compensate the control loop of the buck converter.
PHASE (Pin 8)
Connect this pin to the source of the upper MOSFET and
the drain of the lower MOSFET. This pin is monitored by
the adaptive shoot-through protection circuitry to
determine when the upper MOSFET
is turned
off.
Exposed Pad
Exposed pad should be soldered to PCB board and
connected to GND.
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DS8101/A-01 March 2007
Preliminary
Function Block Diagram
VCC
RT8101/A
Voltage
Reference
Bias
Enable
Power On
Reset (POR)
5V
Regulator
PH_M
+
-
1.5V
5VDD
+
-
POR
0.8V
0.4V
Soft-Start
&
Fault Logic
+
-
UV
30uA
OC
+
-
21.6k
Driver
Logic
0.4V
SSE
INHIBIT
BOOT
UGATE
0.8V
FB
+
+ EA
-
SS
+
+
-
PWM
PHASE
LGATE
Oscillator
COMP
GND
DS8101/A-01 March 2007
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3
RT8101/A
Absolute Maximum Ratings
Preliminary
(Note 1)
Supply Voltage, V
CC
-------------------------------------------------------------------------------------- 16V
BOOT, V
BOOT
- V
PHASE
------------------------------------------------------------------------------------ 16V
PHASE to GND
DC -------------------------------------------------------------------------------------------------------------
−5V
to 15V
< 200ns ------------------------------------------------------------------------------------------------------
−10V
to 30V
BOOT to PHASE ------------------------------------------------------------------------------------------ 15V
BOOT to GND
DC -------------------------------------------------------------------------------------------------------------
−0.3V
to V
CC
+15V
< 200ns ------------------------------------------------------------------------------------------------------
−0.3V
to 42V
UGATE ------------------------------------------------------------------------------------------------------- V
PHASE
−
0.3V to V
BOOT
+ 0.3V
LGATE ------------------------------------------------------------------------------------------------------- GND
−
0.3V to V
CC
+ 0.3V
Input, Output or I/O Voltage ----------------------------------------------------------------------------- GND
−
0.3V to 7V
Power Dissipation, P
D
@ T
A
= 25°C (Note 4)
SOP-8 -------------------------------------------------------------------------------------------------------- 0.83W
SOP-8 (Exposed Pad) ----------------------------------------------------------------------------------- 1.33W
Package Thermal Resistance
SOP-8,
θ
JA
-------------------------------------------------------------------------------------------------- 120°C/W
SOP-8 (Exposed Pad),
θ
JA
------------------------------------------------------------------------------ 75°C/W
Junction Temperature ------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------- 260°C
Storage Temperature Range ----------------------------------------------------------------------------
−
65°C to 150°C
ESD Susceptibility (Note 2)
HBM (Human Body Mode) ------------------------------------------------------------------------------ 2kV
MM (Machine Mode) -------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 3)
Supply Voltage, V
CC
-------------------------------------------------------------------------------------- 12V
±
10%
Junction Temperature Range ----------------------------------------------------------------------------
−
40°C to 125°C
Ambient Temperature Range ----------------------------------------------------------------------------
−
40°C to 85°C
Electrical Characteristics
(V
CC
= 12V, T
A
= 25°C, unless otherwise specified)
Parameter
Supply Input
Supply Voltage
Supply Current
Power-On Reset
POR Threshold
POR Hysteresis
Oscillator
Free Running Frequency
Symbol
V
CC
I
CC
V
CCRTH
V
CCHYS
Test Conditions
UGATE and LGATE Open
V
CC
= 12V
Min
10.8
--
8.8
--
Typ
12
3
9.6
0.8
300
600
Max
13.2
--
10.4
1.6
350
700
Units
V
mA
V
V
kHz
kHz
f
OSC
V
CC
= 12V, RT8101
V
CC
= 12V, RT8101A
250
500
To be continued
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4
DS8101/A-01 March 2007
Preliminary
Parameter
Ramp Amplitude
Reference Voltage
PWM Error Amplifier Reference
Error Amplifier
Open Loop DC Gain
Gain-Bandwidth Product
Slew Rate
A
O
GBW
SR
V
BOOT
−
V
P HASE
= 12V,
V
BOOT
−
V
UGATE
= 6V
V
BOOT
−
V
P HASE
= 12V,
V
BOOT
−
V
UGATE
= 1V
V
BOOT
−
V
PHA SE
= 12V,
V
UGATE
−
V
PHASE
= 1V
V
CC
= 12V, V
LGATE
= 6V
V
CC
−
V
LG ATE
= 1V
V
LGATE
= 1V
Measuring V
FB
V
OC
T
SS
Measuring V
PHAS E
--
--
--
V
REF
0.792
Symbol
ΔV
OSC
Test Conditions
V
CC
= 12V
Min
--
RT8101/A
Typ
1.5
0.8
88
15
6
Max
--
0.808
--
--
--
Units
V
P-P
V
dB
MHz
V/us
PWM Controller Gate Drivers (V
CC
= 12V)
Upper Gate Source
Upper Gate Source
Upper Gate Sink
Lower Gate Source
Lower Gate Source
Lower Gate Sink
Protection
Under Voltage Protection
Over Current Threshold
Soft-Start Interval
0.3
−210
2
0.4
−250
3.2
0.5
−290
4.2
V
mV
ms
I
UGATE
R
UGATE
R
UGATE
I
LGATE
R
LGATE
R
LGATE
--
--
--
--
--
--
300
7
4
500
4
2
--
10
8
--
6
4
mA
Ω
Ω
mA
Ω
Ω
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 high effective 4-layers thermal conductivity test board of
JEDEC 51-7 thermal measurement standard.
DS8101/A-01 March 2007
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