Preliminary |
RT8805C |
Two Phase General Purpose PWM Controller
General Description
The RT8805C is the most compact dual-phase synchronous buck controller in the industry specifically designed for high power density applications. This part is capable of delivering up to 60A output current due to its embedded bootstrapped drivers that support 12V + 12V driving capability.
The phase currents are sensed by innovative time sharing RDS(ON) current sensing technique for current balance and over current balance. Using one common GM amplifier to sense two phase currents eliminates offset and nonlinearity of the GM amplifier and yields good current balance. Other features include adjustable operation frequency from 50kHz to 1MHz, adjustable soft-start, PGOOD, external compensation, enable/shutdown for various application and performance consideration.
The RT8805C comes to a tiny footprint package of VQFN-16L 3x3 package that is capable of dissipating up to 1.47W heat.
Ordering Information
RT8805C 
Package Type
QV : VQFN-16L 3x3 (V-Type)
Operating Temperature Range
P : Pb Free with Commercial Standard
Note :
RichTek Pb-free products are :
`RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
`Suitable for use in SnPb or Pb-free soldering processes. `100% matte tin (Sn) plating.
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.
Features
z12V Power Supply Voltage
z2 Phase Power Conversion
zEmbedded 12V Boot Strapped Driver
zPrecise Core Voltage Regulation
zLow Side MOSFET RDS(ON) Current Sensing for Power Stage Current Balance
zExternal Compensation
zAdjustable Soft-Start
zAdjustable Frequency and Typical at 300kHz Per Phase
zPower Good Indication
zAdjustable Over Current Protection
zSmall 16-Lead VQFN Package
zRoHS Compliant and 100% Lead (Pb)-Free
Applications
zMiddle-High End GPU Core Power
zHigh End Desktop PC Memory Core Power
zLow Output Voltage, High Power Density DC-DC Converters
zVoltage Regulator Modules
Pin Configurations
(TOP VIEW)
|
PHASE1 |
LGATE1 |
VCC |
LGATE2 |
|
|
|
16 |
15 |
14 |
13 |
|
|
UGATE1 |
1 |
|
|
12 |
PHASE2 |
|
BOOT1 |
2 |
GND |
11 |
UGATE2 |
||
AGND |
3 |
10 |
BOOT2 |
|||
|
|
|||||
IMAX |
4 |
|
|
9 |
PGOOD |
|
|
5 |
6 |
7 |
8 |
|
|
|
RT |
SS |
COMP |
FB |
|
|
|
VQFN-16L 3x3 |
|
||||
DS8805C-01 November 2005 |
www.richtek.com |
|
1 |
RT8805C |
Preliminary |
Typical Application Circuit |
|
|
|
|
||||
|
|
|
|
|
|
|
|
VIN |
|
|
R8 |
9 |
RT8805C |
2 |
|
C5 |
|
3.3VCC |
|
PGOOD |
BOOT1 |
|
|
|||
|
R9 |
|
|
|||||
12VCC |
|
14 |
VCC |
|
|
C4 |
|
|
|
|
UGATE1 |
1 |
|
||||
|
|
|
C9 |
|
Q1 |
|
||
|
|
R1 |
5 |
RT |
PHASE1 |
16 |
|
L1 |
|
|
R2 |
|
VOUT |
||||
|
|
4 |
IMAX |
|
15 |
|
|
|
|
|
|
LGATE1 |
Q2 |
|
|||
|
|
|
3 |
AGND |
|
|||
|
|
|
|
|
|
C8 |
||
|
|
|
8 |
|
|
10 |
|
|
|
|
C1 |
FB |
BOOT2 |
|
|
||
|
|
|
|
|
||||
|
|
7 |
|
|
|
|||
|
|
COMP |
|
|
|
|||
|
C2 |
|
|
11 |
C6 |
C7 |
||
|
R3 |
|
|
UGATE2 |
Q3 |
|||
|
|
|
6 |
|
PHASE2 |
12 |
|
L2 |
|
|
|
SS |
|
|
|||
|
|
|
|
|
|
|
|
|
EN |
Q5 |
C3 |
|
GND |
LGATE2 |
13 |
Q4 |
R4 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
R5 |
Function Block Diagram
|
|
|
|
|
VCC |
|
BOOT1 |
|
|
|
PWMCP |
|
|
|
UGATE1 |
PGOOD |
|
|
- |
PWM1 |
|
|
PHASE1 |
|
|
+ |
|
|
|||
|
|
|
Logic |
|
|
VCC |
|
0.8V |
+ |
|
|
|
|
|
LGATE1 |
FB |
-EA |
|
|
|
VCC |
|
BOOT2 |
COMP |
|
|
|
|
|
||
|
External |
|
PWMCP |
|
|
|
UGATE2 |
|
|
+ |
PWM2 |
|
|
PHASE2 |
|
|
Soft Star |
|
|
|
|||
|
|
- |
Logic |
|
|
||
|
|
|
|
|
VCC |
||
SS |
|
|
|
|
|
|
LGATE2 |
|
CLK1 |
RAMP1 RAMP2 |
CLK2 |
|
|
|
|
AGND |
|
Current |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Balance |
|
- |
MUX |
PHASE2 |
|
|
|
|
S/H |
PHASE1 |
|||
|
|
|
GM |
|
|
||
IMAX |
|
OCP |
|
+ |
|
|
|
|
|
|
|
To PWM Logic |
|||
|
|
|
|
|
|
||
VCC |
Reg |
OC |
|
|
|
|
|
VDD |
|
|
|
|
Central |
||
|
|
|
|
PGOOD |
|
||
|
|
|
|
|
Logic |
||
|
|
CLK1 |
|
|
|
|
|
RT |
Clock |
|
|
|
|
|
|
CLK2 |
|
|
|
|
|
||
|
|
|
|
|
|
OC |
|
|
|
|
|
|
|
|
|
|
|
GND |
|
|
|
|
|
www.richtek.com |
|
|
|
|
|
|
DS8805C-01 November 2005 |
2
Preliminary |
RT8805C |
Functional Pin Description
UGATE1 (Pin 1), UGATE2 (Pin 11)
UpperGateDrive. These pins drive the gates of the highside MOSFETs.
BOOT1 (Pin 2), BOOT2 (Pin 10)
Bootstrap Power Pin. These pins power the high-side MOSFET drivers. Connect These pins to the junctions of the bootstrap capacitors.
AGND (Pin 3)
Chip Analog Ground.
IMAX (Pin 4)
Maximum Current Setting. This pin sets the current limiting level. Connect this pin with resistor to ground to set the current limit.
RT (Pin 5)
Timing Resistor. Connect a resistor from RT to AGND to set the clock frequency.
SS (Pin 6)
Soft-Start Pin. This pin provides soft-start function for controller. The COMP voltage of the converter follows the ramping voltage on the SS pin.
COMP (Pin 7)
Compensation Pin. This pin is output node of the error amplifier.
FB (Pin 8)
Feedback Pin. This pin is negative input pin of the error amplifier.
PGOOD (Pin 9)
Power Good. PGOOD is an open drain output used to indicate the status of the voltages on SS pin and FB pin. PGOOD will go high impedance when SS > 3.7V and FB > 0.6V.
LGATE1 (Pin 15), LGATE2 (Pin 13)
Lower Gate Drive. These pins drive the gate of the lowside MOSFETs.
PHASE1 (Pin 16), PHASE2 (Pin 12)
These pins are return nodes of the high-side driver. Connect These pins to high-side MOSFET sources together with the low-side MOSFET drains and the inductors.
VCC (Pin 14)
The VCC pin is the external 12V power. Internal 5V power (VDD) is regulated from this pin. This pin also powers the low side MOSFETS drivers.
GND (Exposed Pad)
Exposed pad should be soldered to PCB board and connected to GND.
DS8805C-01 November 2005 |
www.richtek.com |
|
3 |
RT8805C |
Preliminary |
Absolute Maximum Ratings |
(Note 1) |
z Supply Voltage, VCC -------------------------------------------------------------------------------------------------- |
−0.3V to 16V |
z PHASE to GND |
|
DC ------------------------------------------------------------------------------------------------------------------------- |
−5V to 15V |
< 200ns ------------------------------------------------------------------------------------------------------------------ |
−10V to 30V |
z BOOT to PHASE ------------------------------------------------------------------------------------------------------ |
15V |
z BOOT to GND |
|
DC ------------------------------------------------------------------------------------------------------------------------- |
−0.3V to VCC+15V |
< 200ns ------------------------------------------------------------------------------------------------------------------ |
−0.3V to 42V |
z Input, Output or I/O Voltage ----------------------------------------------------------------------------------------- |
GND-0.3V to 7V |
z Power Dissipation, PD @ TA = 25°C |
|
VQFN−16L 3x3 --------------------------------------------------------------------------------------------------------- |
1.47W |
z Package Thermal Resistance (Note 4) |
|
VQFN−16L 3x3, θJA --------------------------------------------------------------------------------------------------- |
68°C/W |
z Junction Temperature ------------------------------------------------------------------------------------------------- |
150°C |
z Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- |
260°C |
z ESD Susceptibility (Note 2) |
|
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ |
1.5kV |
MM (Machine Mode) -------------------------------------------------------------------------------------------------- |
200V |
Recommended Operating Conditions (Note 3) |
|
z Supply Voltage --------------------------------------------------------------------------------------------------------- |
9V to 14V |
z Junction Temperature Range ---------------------------------------------------------------------------------------- |
−20°C to 70°C |
Electrical Characteristics
(VIN = 12V, TA = 25°C, unless otherwise specified)
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Units |
|
Supply Input |
|
|
|
|
|
|
|
Power Supply Voltage |
VCC |
|
-- |
12 |
15 |
|
V |
|
|
|
|
|
|
|
|
Power On Reset |
VCC |
|
5.4 |
5.9 |
6.5 |
|
V |
Power On Reset Hysteresis |
|
|
-- |
0.3 |
-- |
|
V |
|
|
|
|
|
|
|
|
Power Supply Current |
IVCC |
VSS = 0V |
-- |
10 |
-- |
|
mA |
Soft Start |
|
|
|
|
|
|
|
Soft Start Current |
ISS |
|
8 |
10 |
15 |
|
μA |
Oscillator |
|
|
|
|
|
|
|
Free Running Frequency |
fOSC |
RT = 33kΩ |
255 |
300 |
345 |
|
kHz |
Frequency Variation |
|
|
-15 |
-- |
15 |
|
% |
Frequency Range |
|
|
50 |
300 |
1000 |
|
kHz |
Maximum Duty Cycle |
|
|
70 |
75 |
80 |
|
% |
|
|
|
|
|
To be continued |
||
|
|
|
|
|
|
|
|
www.richtek.com |
|
|
DS8805C-01 |
November |
2005 |
||
4
|
Preliminary |
|
RT8805C |
|||
|
|
|
|
|
|
|
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Units |
Reference Voltage |
|
|
|
|
|
|
Feedback Voltage |
VFB |
VFB = 0.8V |
0.784 |
0.8 |
0.816 |
V |
Error Amplifier |
|
|
|
|
|
|
|
|
|
|
|
|
|
DC Gain |
|
|
60 |
70 |
-- |
dB |
|
|
|
|
|
|
|
Gain-Bandwidth Product |
GBW |
CLOAD = 5pF |
6 |
10 |
-- |
MHz |
Trans-conductance |
GM |
RLOAD = 20kΩ |
600 |
660 |
-- |
μA/V |
MAX Current (Source & Sink) |
ICOMP |
VCOMP = 2.5V |
300 |
360 |
-- |
μ |
|
|
|
|
A |
||
Current Sense GM Amplifier |
|
|
|
|
|
|
|
|
|
|
|
|
|
OC |
VPHASE |
RIMAX = 33kΩ |
-- |
-220 |
-- |
mV |
Gate Driver |
|
|
|
|
|
|
Maximum Upper Drive Source |
IUGATE(MAX) |
BOOT − PHASE = 12V |
1 |
-- |
-- |
A |
Upper Drive Sink |
RUGATE |
VUGATE = 1V |
-- |
3.5 |
7 |
Ω |
Maximum Lower Drive Source |
ILGATE(MAX) |
PVCC = 12V |
1 |
-- |
-- |
A |
Lower Drive Sink |
RLGATE |
VLGATE = 1V |
-- |
2 |
4 |
Ω |
Protection |
|
|
|
|
|
|
|
|
|
|
|
|
|
Under Voltage Protection |
|
|
0.55 |
0.6 |
0.65 |
V |
|
|
|
|
|
|
|
Power Sequence |
|
|
|
|
|
|
|
|
|
|
|
|
|
Power Good Threshold |
|
|
3.4 |
3.7 |
4 |
V |
|
|
|
|
|
|
|
Power Good Sink Capability (4mA) |
|
|
-- |
0.05 |
0.2 |
V |
|
|
|
|
|
|
|
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. θJA is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard.
DS8805C-01 November 2005 |
www.richtek.com |
|
5 |
Loading...