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RT8208BGQW

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18
RT8208A/B
1
DS8208A/B-04 May 2011 www.richtek.com
Programmable Output Voltage Single Synchronous
Buck Controller
General Description
The RT8208A/B is a constant-on-time PWM controller
which provides four resistor programmable DC output
voltages by controlling the G0 and G1 digital input. The
output voltage is programmable from 0.75V to 3.3V. The
RT8208A/B offers the lowest total solution cost in systems
where need output voltage slewing. The RT8208A/B
provides an automatic masking power good output during
output voltage transition.
The constant-on-time PWM control scheme handles wide
input/output ratios with ease and provides 100ns “instant-
on” response to load transient while maintaining a
relatively constant frequency. It provides the high efficiency,
excellent transient response, and DC output accuracy
needed for stepping down high voltage batteries to
generate low voltage CPU core, graphics, I/O and chipset
RAM supplies in notebook computers.
The RT8208A/B achieves high efficiency at a reduced cost
by eliminating the current sense resistor 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 from high voltage batteries for the highest
possible efficiency. Additional features include soft-start,
under voltage protection, programmable over current
protection and non-overlapping gate drive. The RT8208A/
B is available in a WQFN-16L 3x3 package.
Features
zz
zz
z Ultra-High Efficiency
zz
zz
z Resistor Programmable Output Voltage from 0.75V
to 3.3V with Integrated Transition Support
zz
zz
z Quick Load Step Response within 100ns
zz
zz
z 1% V
FB
Accuracy over Line and Load
zz
zz
z 4.5V to 26V Battery Input Range
zz
zz
z Resistor Programmable Frequency
zz
zz
z Integrated Bootstrap Switch
zz
zz
z Resistor Programmable Positive Current Limit by
Low Side R
DS(ON)
Sense (Lossless Limit)
zz
zz
z Negative Current Limiter
zz
zz
z Voltage Transient Overshoot Eliminator*
zz
zz
z Over Voltage Protection
zz
zz
z Under Voltage Protection
zz
zz
z 4 Steps Current Limit During Soft-Start
zz
zz
z Power Good Indicator
zz
zz
z RoHS Compliant and Halogen Free
Applications
z Notebook Computers
z System Power Supplies
z I/O Supplies
z Programmable-Output Power Supplies
Ordering Information
* Paten Pending
Note :
Richtek 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.
Pin Configurations
WQFN-16L 3x3
(TOP VIEW)
PGOOD
FB
VOUT
VDD
UGATE
PHASE
VDDP
CS
D1
G0
D0
LGATE
TON
EN/DEM
BOOT
G1
12
11
10
9
13141516
1
2
3
4
8765
GND
17
RT8208
Package Type
QW : WQFN-16L 3x3 (W-Type)
Turn-on D0/D1 MOSFET
A : G0/G1 High
B : G0/G1 Low
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
RT8208A/B
2
DS8208A/B-04 May 2011www.richtek.com
Typical Application Circuit
Marking Information
FF= : Product Code
YMDNN : Date Code
RT8208AGQW
FG= : Product Code
YMDNN : Date Code
FF : Product Code
YMDNN : Date Code
FG : Product Code
YMDNN : Date Code
RT8208AZQW
RT8208BGQW
RT8208BZQW
FF=YM
DNN
FF YM
DNN
FG=YM
DNN
FG YM
DNN
Functional Pin Description
Pin No. Pin Name Pin Function
1 VOUT
Output Voltage Pin. Connect to the output of PWM converter. VOUT is an input of
the PWM controller.
2 VDD
Analog supply voltage input for the internal analog integrated circuit. Bypass to
GND with a 1μF ceramic capacitor.
3 FB
Feedback Input Pin. Connect FB to a resistor voltage divider from VOUT to GND
to adjust output voltage from 0.75V to 3.3V
4 PGOOD
Power good signal open-drain output of PWM converter. This pin will be pulled
high when the output voltage is within the target range.
5 D1 Drain of the internal MOSFET which is controlled by G1.
6 D0 Drain of the internal MOSFET which is controlled by G0.
To be continued
V
I
N
P
G
O
O
D
V
D
D
P
R
2
R
1
C
2
R
3
Q
1
Q
2
C
1
V
O
U
T
=
0
.
9
V
R
6
2
5
0
k
1
0
1
0
0
k
1
µ
F
1
8
k
0
R
4
R
5
C
3
0
0
.
1
µ
F
4
.
5
V
t
o
2
6
V
B
S
C
1
1
9
N
0
3
S
C
4
1
0
µ
F
R
7
C
7
R
8
R
9
L
1
1
µ
H
C
5
*
C
6
*
2
2
0
µ
F
1
0
1
2
1
1
8
3
V
D
D
P
C
S
U
G
A
T
E
F
B
RT8208A/B
L
G
A
T
E
9
1
3
B
O
O
T
P
H
A
S
E
V
O
U
T
1
V
D
D
2
P
G
O
O
D
4
T
O
N
1
6
R
1
0
0
1
2
k
C
C
M
/
D
E
M
EN/DEM
1
5
G
N
D
1
7
(
E
x
p
o
s
e
d
P
a
d
)
*
:
O
p
t
i
o
n
a
l
6
0
k
7
G
0
G
0
1
4
G
1
G
1
5
D
1
6
D
0
R
1
1
*
R
1
2
*
B
S
C
1
1
9
N
0
3
S
RT8208A/B
3
DS8208A/B-04 May 2011 www.richtek.com
Function Block Diagram
Min. T
OFF
QTRIG
1-SHOT
+
-
+
-
GM
0.75V V
REF
SQ
Latch
SQ
Latch
+
-
OV
+
-
UV
125% V
REF
70% V
REF
+
-
90% V
REF
SS Timer
Thermal
Shutdown
Diode
Emulation
DRV
DRV
On-time
Compute
1-SHOT
CS
FB
VOUT
VDD
UGATE
PHASE
VDDP
PGOOD
GND
LGATE
TON
BOOT
TRIG
EN
R
QS
SS
(internal)
Control
Logic
G0 G1 D0 D1
R
R
G0, G1
Counter
Blanking Signal
EN
-
+
GM
+
-
10µA
Pin No. Pin Name Pin Function
7 G0
Control Input Pin for the D0 MOSFET. A logic high for RT8208A and low for
RT8208B turn on the D0 MOSFET on, pulling D0 to the ground.
8 LGATE
Low side N-MOSFET gate driver output for PWM. This pin swings between GND
and VDDP.
9 VDDP
VDDP is the gate driver supply for external MOSFETs. Bypass to GND with a 1μF
ceramic capacitor.
10 CS
Over Current Trip Point Set Input. Connect a resistor from this pin to signal ground
to set threshold for both over current and negative over current limit.
11 PHASE
The UGATE High Side Gate Driver Return. Also serves as anode of over current
comparator.
12 UGATE
High side N-MOSFET floating gate driver output for the PWM converter. This pin
swings between PHASE and BOOT.
13 BOOT
Boost Capacitor Connection for PWM Converter. Connect to an external ceramic
capacitor to PHASE.
14 G1
Control Input Pin for the D1 MOSFET. A logic high for RT8208A and low for
RT8208B turn on the D1 MOSFET on, pulling D1 to the ground.
15 EN/DEM
Enable/Diode Emulation Mode Control Input. Connect to VDD for diode–emulation
mode, connect to GND for shutdown and floating the pin for CCM mode.
16 TON
On Time/Frequency Adjustment Pin. Connect to PHASE through a resistor. TON is
an input for the PWM controller.
17 (Exposed pad) GND
The exposed pad must be soldered to a large PCB and connected to GND for
maximum power dissipation.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

RT8208BGQW

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Description:
IC REG CTRLR BUCK 16WQFN
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New from this manufacturer.
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