RT8800/B
General Purpose 2/3-Phase PWM Controller for High-Density
Power Supply
General Description
The RT8800/B are general purpose multi-phase
synchronous buck controllers dedicating for high density
power supply regulation. The parts implement 2, and 3
buck switching stages operating in interleaved phase set
automatically. The output voltage is regulated and
controlled following the input voltage of FB pin. With such
a single analog control, the RT8800/B provide a simple,
flexible, wide-range and extreme cost-effective high-
density voltage regulation solutions for various high-density
power supply application. The RT8800/B multi-phase
architecture provide high output current while maintaining
low power dissipation on power devices and low stress
on input and output capacitors. The high equivalent
operating frequency also reduces the component
dimension and the output voltage ripple in load transient.
RT8800/B implement both voltage and current loops to
achieve good regulation, response and power stage
thermal balance. The RT8800/B apply the time sharing
DCR current sensing technology newly as well; with such
a topology, the RT8800/B extract the DCR of output
inductor as sense component to deliver a more precise
load line regulation and better thermal balance capability.
Moreover, the parts monitor the output voltage for over-
current and over-voltage protection; Soft-start and
programmable under-voltage lockout are also provided to
assure the safety of power system.
Features
5V Power Supply Voltage
2/3-Phase Power Conversion with Automatic Phase
Selection (RT8800 : 2/3-Phase, RT8800B : 2-Phase)
Output Voltage Controlled by External Reference
Voltage
Precise Core Voltage Regulation
Power Stage Thermal Balance by DCR Current
Sensing
Extreme Low-Cost, Lossless Time Sharing Current
Sensing
Internal Soft-start
Hiccup Mode Over-Current Protection
Over-Voltage Protection
Adjustable Operating Frequency and Typical at
300kHz Per Phase
Power Good indication
Small 16-Lead VQFN Package (For RT8800 only)
RoHS Compliant and 100% Lead (Pb)-Free
Ordering Information
RT8800/B
Package Type
QV : VQFN-16L 3x3 (V-Type)
S : SOP-16
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
2-Phase
2/3-Phase
Applications
Desktop CPU core power
Low Output Voltage, High power density DC-DC
Converters
Voltage Regulator Modules
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.
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
DS8800/B-08 April 2011
www.richtek.com
1
RT8800/B
Pin Configurations
(TOP VIEW)
PWM3
PWM2
PWM1
VDD
16 15 14 13
DACFB
DACQ
FB
DVD
1
2
3
4
5
6
7
8
12
ISP1
ISP2
ISP3
PGOOD
GND
17
11
10
9
RT
ICOMMON
COMP
VDD
DACFB
DACQ
FB
DVD
COMP
PI
RT
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
PWM2
PWM1
N/C
ISP
1
ISP
2
PGOOD
GND
ICOMMON
PI
SOP-16
RT8800B
VQFN-16L 3x3
RT8800
Functional Pin Description
DACFB
Negative input of internal buffer amplifier for reference
voltage regulation. The pin voltage is locked at internal
V
REF
= 0.8V by properly close the buffer amplifier feedback
loop.
DACQ
The pin is defined as the output of internal buffer amplifier
for reference voltage regulation.
FB
The pin is defined as the inverting input of internal error
amplifier.
DVD
The pin is defined as a programmable power UVLO
detection input. Trip threshold = 0.8V at V
DVD
rising.
COMP
The pin is defined as the output of the error amplifier and
the input of all PWM comparators.
PI
The pin is defined as the positive input of the error amplifier.
RT
Switching frequency setting. Connect this pin to GND with
a resistor to set the frequency.
VDD
Chip power supply. Connect this pin to a 5V supply.
GND
Chip power ground.
Exposed Pad (17) (RT8800)
The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
ICOMMON
Common negative input of current sense amplifiers for all
three channels.
PGOOD
Output power-good indication. The signal is implemented
as an output signal with open-drain type.
ISP1 , ISP2 , ISP3
Current sense positive inputs for individual converter
channel current sense.
PWM1 , PWM2 , PWM3
PWM outputs for each phase switching drive.
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DS8800/B-08 April 2011
Wireless Connectivity
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