RT8202/A/B
Single Synchronous Buck Controller
General Description
The RT8202/A/B PWM controller provides high efficiency,
excellent transient response, and high DC output accuracy
needed for stepping down high voltage batteries to
generate low voltage CPU core, I/O, and chipset RAM
supplies in notebook computers.
The constant on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides 100ns
“instant-on”
response to load transients while maintaining
a relatively constant switching frequency.
The RT8202/A/B achieves high efficiency at a reduced
cost by eliminating the current sense resistor found in
traditional current mode PWMs. Efficiency is further
enhanced by its ability to drive very large synchronous
rectifier MOSFETs. The buck conversion allows this device
to directly step down high voltage batteries for the highest
possible efficiency. The RT8202/A/B is intended for CPU
core, chipset, DRAM, or other low voltage supplies as
low as 0.75V. RT8202 is available in WQFN-16L 4x4,
RT8202A is available in WQFN-16L 3x3 and RT8202B is
available in WQFN-14L 3.5x3.5 packages.
Features
Ultra-High Efficiency
Resistor Programmable Current Limit by Low Side
R
DS(ON)
Sense (Lossless Limit) or Sense Resistor
(High Accuracy)
Quick Load Step Response within 100ns
1% V
OUT
Accuracy over Line and Load
Adjustable 0.75V to 3.3V Output Range
4.5V to 26V Battery Input Range
Resistor Programmable Frequency
Over/Under Voltage Protection
2 Steps Current Limit During Soft-Start
Drives Large Synchronous-Rectifier FETs
Power Good Indicator
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Notebook Computers
CPU Core Supply
Chipset/RAM Supply as Low as 0.75V
Pin Configurations
(TOP VIEW)
TON
EN/DEM
NC
BOOT
12
Ordering Information
RT8202/A/B
Package Type
QW : WQFN-16L 4x4 (W-Type) (RT8202)
QW : WQFN-16L 3x3 (W-Type) (RT8202A)
QW : WQFN-14L 3.5x3.5 (W-Type) (RT8202B)
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
16 15 14 13
VOUT
VDD
FB
PGOOD
1
2
3
4
5
6
7
8
UGATE
PHASE
OC
VDDP
GND
17
11
10
9
Note :
Richtek Pb-free and Green products are :
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
RoHS compliant and compatible with the current require-
WQFN-16L 4x4/WQFN-16L 3x3
EN/DEM
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area, otherwise visit our website for detail.
DS8202/A/B-03 April 2010
TON
VOUT
VDD
FB
PGOOD
1
2
3
4
5
6
7
14
BOOT
GND
15
8
PGND
LGATE
UGATE
PHASE
11
OC
10
VDDP
9
LGATE
13
12
NC
GND
WQFN-14L 3.5x3.5
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1
PGND
GND
RT8202/A/B
Typical Application Circuit
V
DDP
5V
C1
1µF
R2
51k
D1
BAT254
R3
1M
RT8202/A/B
BOOT
TON
VDDP
R1
10
VDD
C2
1µF
PGOOD
CCM/DEM
PGOOD
EN/DEM
GND
PGND
VOUT
UGATE
PHASE
LGATE
OC
FB
C8
0.1µF
R9
20k
R6 10k
Q2
AO4702
R4
2.2
R5 0
C3
0.1µF
C4
10µF
Q1
AO4702
V
OUT
1.2V
L1
2.4µH
C7
220µF
V
IN
4.5V to 26V
R7
C5
R8
12k
C6
Functional Pin Description
Pin No.
RT8202/A
RT8202B
1
2
3
4
3
4
5
6
Pin Name
VOUT
VDD
FB
PGOOD
Pin Function
VOUT Sense Input. Connect to the output of PWM converter. VOUT is an
input of the PWM controller.
Analog Supply Voltage Input for the internal analog integrated circuit.
Bypass to GND with a 1μF ceramic capacitor.
VOUT Feedback Input. Connect FB to a resistor voltage divider from
VOUT to GND to adjust the output from 0.75V to 3.3V.
Power Good Signal Open-Drain Output of PWM Converter. This pin will
be pulled high when the output voltage is within the target range.
No Internal Connection.
Ground for Analog Circuitry.
The exposed pad must be soldered to a large
PCB and connected to GND for maximum power dissipation.
Power Ground.
Low side N-MOSFET Gate-Drive Output for PWM. This pin swings
between GND and VDDP.
VDDP is the gate driver supply for the external MOSFETs. Bypass to
GND with a 1μF ceramic capacitor.
PWM Current Limit Setting and sense. Connect a resistor between OC to
PHASE for current limit setting.
Inductor Connection. This pin is not only the zero-current-sense input for
the PWM converter, but also the UGATE high side gate driver return.
High Side N-MOSFET Floating Gate-Driver Output for the PWM
converter. This pin swings between PHASE and BOOT.
Boost Capacitor Connection for PWM Converter. Connect an external
ceramic capacitor to PHASE and an external diode to VDDP.
PWM Enable and Operation Mode Selection Input. Connect to VDD for
diode-emulation mode, connect to GND for shutdown mode and floating
the pin for CCM mode.
VIN Sense Input. Connect to VIN through a resistor. TON is an input of
the PWM controller.
DS8202/A/B-03 April 2010
5, 14
--
NC
6,
7,
Exposed Pad Exposed Pad GND
(17)
(15)
7
8
PGND
8
9
10
11
12
13
15
16
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2
9
10
11
12
13
14
1
2
LGATE
VDDP
OC
PHASE
UGATE
BOOT
EN/DEM
TON
RT8202/A/B
Function Block Diagram
VOUT
TON
TRIG
On-time
Compute
1-SHOT
SS(Internal)
- +
GM
+
-
-
+
R
Comp
S
Q
BOOT
DRV
UGATE
PHASE
0.75V V
REF
+
Q
OV
Latch
S1
Q
Latch
S1
Q
-
Min. T
OFF
TRIG
1-SHOT
DRV
VDDP
LGATE
PGND
Diode
Emulation
115% V
REF
FB
70% V
REF
-
-
+
UV
90% V
REF
VDD
GND
SS Timer
+
20uA
Thermal
Shutdown
+
-
OC
EN/DEM
PGOOD
DS8202/A/B-03 April 2010
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3
RT8202/A/B
Absolute Maximum Ratings
(Note 1)
−
0.3V to 32V
−
0.3V to 38V
−
6V to 0.3V
−
0.3V to 6V
−
0.3V to 6V
−
0.3V to 32V
−
0.3V to 6V
PGND to GND --------------------------------------------------------------------------------------------------------------
−
0.3V to 0.3V
Input Voltage, TON to GND ----------------------------------------------------------------------------------------------
BOOT to GND --------------------------------------------------------------------------------------------------------------
PHASE to BOOT ----------------------------------------------------------------------------------------------------------
VDD, VDDP, VOUT, EN/DEM, FB, PGOOD to GND --------------------------------------------------------------
UGATE to PHASE --------------------------------------------------------------------------------------------------------
OC to GND ------------------------------------------------------------------------------------------------------------------
LGATE to GND -------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
WQFN-16L 4x4 ------------------------------------------------------------------------------------------------------------ 1.852W
WQFN-16L 3x3 ------------------------------------------------------------------------------------------------------------ 1.471W
WQFN-14L 3.5x3.5 ------------------------------------------------------------------------------------------------------- 1.667W
Package Thermal Resistance (Note 2)
WQFN-16L 4x4,
θ
JA
------------------------------------------------------------------------------------------------------- 54°C/W
WQFN-16L 4x4,
θ
JC
------------------------------------------------------------------------------------------------------ 7°C/W
WQFN-16L 3x3,
θ
JA
------------------------------------------------------------------------------------------------------- 68°C/W
WQFN-16L 3x3,
θ
JC
------------------------------------------------------------------------------------------------------
WQFN-14L 3.5x3.5,
θ
JA
--------------------------------------------------------------------------------------------------
WQFN-14L 3.5x3.5,
θ
JC
-------------------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------
Junction Temperature ----------------------------------------------------------------------------------------------------
Storage Temperature Range --------------------------------------------------------------------------------------------
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ----------------------------------------------------------------------------------------------
MM (Machine Mode) ------------------------------------------------------------------------------------------------------
7.5°C/W
60°C/W
7°C/W
260°C
150°C
−
65°C to 150°C
2kV
200V
Recommended Operating Conditions
(Note 4)
4.5V to 26V
4.5V to 5.5V
−40°C
to 125°C
−40°C
to 85°C
Input Voltage, V
IN
----------------------------------------------------------------------------------------------------------
Supply Voltage, V
DD
, V
DDP
----------------------------------------------------------------------------------------------
Junction Temperature Range --------------------------------------------------------------------------------------------
Ambient Temperature Range --------------------------------------------------------------------------------------------
Electrical Characteristics
(V
DD
= V
DDP
= 5V, V
IN
= 15V, V
OUT
= 1.25V, EN/DEM = V
DD
, R
TON
= 1MΩ, T
A
= 25°C, unless otherwise specified)
Parameter
PWM Controller
Quiescent Supply Current
TON Operating Current
Shutdown Current
Symbol
Test Conditions
Min
Typ
Max
Unit
VDD + VDDP, FB = 0.8V
R
TON
= 1M
I
SHDN
VDD + VDDP
TON
EN/DEM = 0V
--
--
--
--
−10
--
15
1
1
−1
1250
--
10
5
--
μA
μA
μA
μA
μA
To be continued
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4
DS8202/A/B-03 April 2010
RT8202/A/B
Parameter
FB Reference Voltage
FB Input Bias Current
Output Voltage Range
On-Time
Minimum Off-Time
V
OUT
Shutdown Discharge
Resistance
Current Sensing
ILIM Source Current
Current Comparator Offset
Current Limit Setting Range R
ILIM
Zero Crossing Threshold
Fault Protection
Current Limit Sense
Voltage
Output UV Threshold
OVP Threshold
OV Fault Delay
VDD UVLO Threshold
Soft-Start Ramp Time
UV Blank Time
Thermal Shutdown
Thermal Shutdown
Hysteresis
Driver On-Resistance
UGATE Driver Pull Up
UGATE Driver Sink
LGATE Driver Pull Up
LGATE Driver Pull Down
UGATE Driver Source/Sink
Current
LGATE Driver Source
Current
LGATE Driver Sink Current
Dead Time
UGATE Rising
--
30
--
To be continued
DS8202/A/B-03 April 2010
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5
Symbol
V
FB
Test Conditions
V
DD
= 4.5 to 5.5V
FB = 0.75V
Min
0.742
−1
0.75
Typ
0.75
0.1
--
334
400
20
Max
0.758
1
3.3
401
550
--
Unit
V
μA
V
ns
ns
Ω
V
OUT
V
IN
= 15V, V
OUT
= 1.25V, R
TON
= 1M
267
250
EN/DEM = GND
--
LGATE = High
GND
−
OC
18
−10
2.5
20
--
--
--
22
10
10
5
μA
mV
kΩ
mV
GND
−
PHASE, EN/DEM = 5V
GND
−
PHASE, R
ILIM
= 2.5k
GND
−
PHASE, R
ILIM
= 10k
With respect to error comparator
threshold
FB forced above OV threshold
Rising edge, Hysteresis = 20mV,
PWM disabled below this level
From EN high to internal V
REF
reach
0.71V (0 95%)
From EN signal going high
−10
V
RILIM
35
170
60
10
--
4.1
--
--
--
--
50
200
70
15
20
4.3
1.35
3.1
155
10
65
230
80
20
--
4.5
--
--
--
--
mV
mV
%
%
μs
V
ms
ms
°C
°C
BOOT
−
PHASE = 5V
R
UGATEsk
BOOT
−
PHASE = 5V
LGATE, High State (Source)
LGATE, Low State (Sink)
UGATE
−
PHASE = 2.5V,
BOOT
−
PHASE = 5V
LGATE forced to 2.5V
LGATE forced to 2.5V
LGATE Rising (PHASE = 1.5V)
--
--
--
--
--
--
--
--
1.5
1.5
1.5
0.6
1
1
3
30
5
5
5
2.5
--
--
--
--
Ω
Ω
Ω
Ω
A
A
A
ns
PCB Design
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