RT8803A
2/3-Phase PWM Controller for High-Density Power Supply
General Description
The RT8803A is a 2/3-phase synchronous buck controller
specifically designed to power Intel
®
/ AMD next generation
microprocessors. It implements an internal 8-bit DAC that is
identified by VID code of microprocessor directly. RT8803A
generates VID table that conform to Intel
®
VRD10.x and
VRD11 core power with 6.25mV increments and 0.5%
accuracy.
RT8803A adopts innovative time-sharing DCR current sensing
technique to sense phase currents for phase current balance,
load line setting and over current protection. Using a common
GM to sense all phase currents eliminates offset and linearity
variation between GMs in conventional current sensing
methods. As sub-milli-ohm-grade inductors are widely used
in modern motherboards, slight offset and linearity mismatch
will cause considerable current shift between phases. This
technique ensures good current balance at mass production.
Other features include over current protection, programmable
soft start, over voltage protection, and output offset setting.
RT8803A comes to a small footprint package with
VQFN-32L 5x5.
Features
5V Power Supply
2/3-Phase Power Conversion with Automatic Phase
Selection
8-bit VID Interface, Supporting Intel VRD11/VRD10.x
and AMD K8, K8_M2 CPUs
VR_HOT and VR_FAN Indication
Precision Core Voltage Regulation
Power Stage Thermal Balance by DCR Current
Sensing
Adjustable Soft-start
Over-Voltage Protection
Adjustable Frequency and Typical at 300kHz per
Phase
Power Good Indication
32-Lead VQFN Package
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Intel
®
/AMD New generation microprocessor for Desktop
PC and Motherboard
Low Output Voltage, High power density DC-DC
Converters
Voltage Regulator Modules
Ordering Information
RT8803A
Package Type
QV : VQFN-32L 5x5 (V-Type)
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
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
(TOP VIEW)
VID_SEL
VID0
VID1
VID2
VID3
VID4
27
VID5
26
32
31
30
29
28
25
24
23
22
VTT/EN
VR_Ready
FBRTN
FB
COMP
SS
VR_FAN
VR_HOT
VID6
21
20
19
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
33
GND
VID7
VDD
PWM3
PWM2
PWM1
ISP1
ISP2
ISP3
18
17
IMAX
RT
ISN1
VQFN-32L 5x5
DS8803A-06 April 2011
ISN23
TSEN
DVD
OFS
ADJ
www.richtek.com
1
RT8803A
Functional Pin Description
OFS (Pin 12)
VTT/EN (Pin 1)
The pin is defined as the chip enable, and the VTT is
applied for internal VID pull high power and power sequence
monitoring.
VR_Ready (Pin 2)
Power good open-drain output.
FBRTN (Pin 3)
Feedback return pin. VID DAC and error amplifier reference
for remote sensing of the output voltage.
FB (Pin 4)
Inverting input pin of the internal error amplifier.
COMP (Pin 5)
Output pin of the error amplifier and input pin of the PWM
comparator.
SS (Pin 6)
Connect this SS pin to GND with a capacitor to set the
soft-start time interval.
VR_FAN (Pin 7)
The pin is defined to signal VR thermal information for
external VR thermal dissipation scheme triggering.
VR_HOT (Pin 8)
The pin is defined to signal VR thermal information for
external VR thermal dissipation scheme triggering.
TSEN (Pin 9)
Temperature detect pin for VR_HOT and VR_FAN.
DVD (Pin 10)
Programmable power UVLO detection input. Trip threshold
is 1V at V
DVD
rising.
RT (Pin 11)
The pin is defined to set internal switching operation
frequency. Connect this pin to GND with a resistor R
RT
to
set the frequency F
SW
.
F
SW
=
4.463 e
9
R
RT
+
3500
The pin is defined for load line offset setting.
ADJ (Pin 13)
Current sense output for active droop adjusting. Connect
a resistor from this pin to GND to set the load droop.
IMAX (Pin 14)
The pin is defined to set threshold of over current.
ISN1 (Pin 15)
Current sense negative input pin for channel 1 current
sensing.
ISN23 (Pin 16)
Current sense negative input pins for channel 2 and
channel 4 current sensing.
ISP1 (Pin 19), ISP2
(Pin 18), ISP3 (Pin 17)
Current sense positive input pins for individual converter
channel current sensing.
PWM1 (Pin 20), PWM2 (Pin 21), PWM3 (Pin 22)
PWM outputs for each driven channel. Connect these pins
to the PWM input of the MOSFET driver. For systems
which using 2/3/4 channels, pull PWM 3/4/5 pins up to
high.
VDD (Pin 23)
IC power supply. Connect this pin to a 5V supply.
VID7 (Pin 24), VID6 (Pin 25), VID5 (Pin 26), VID4 (Pin
27), VID3 (Pin 28), VID2 (Pin 29), VID1 (Pin 30),
VID0 (Pin 31), VID_SEL (32)
DAC voltage identification inputs for VRD10.x / VRD11 /
K8 / K8_M2 . These pins are internally pulled up to VTT.
VIDSEL
VTT
GND
VDD
VDD
VID [7]
X
X
NC
GND
Table
VR11
VR10.x
K8
K8_M2
GND [Exposed pad (33)]
The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
www.richtek.com
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DS8803A-06 April 2011
京公网安备 11010802033920号
EEWORLD
