Richtek RT7291AGQUF, RT7291BGQUF Schematic [ru]
®
RT7291A/B
6A, 23V, 500kHz, ACOTTM Synchronous Buck Converter with LDO for System 5V
General Description
The RT7291A/B is a synchronous Buck converter with Advanced Constant On-Time (ACOTTM) mode control. The main control loop of RT7291A/B uses an ACOTTM mode control which provides a very fast transient response with no external compensators. The RT7291A/B operates from 5V to 23V input voltage, provides a 5V LDO and a 300kHz CLK to drive an external charge pump. OCP, UVP and OVP are included in the RT7291A/B. This IC also provides a 1.5ms internal soft-start function and an open-drain power good indicator.
Applications
Laptop Computers
Tablet PCs
Networking Systems
Servers
Personal Video Recorders
Flat Panel Television and Monitors
Distributed Power Systems
Features
5V to 23V Input Voltage Range
Up to 98% Duty for 2S Battery Application
PWM Frequency Fixed 500kHz
ACOTTM Mode Performs Fast Transient Response
Integrated MOSFETs
31mΩ of High-Side MOSFET
20mΩ of Low-Side MOSFET
Support Output MLCC Stable
Internal Soft-Start (1.5ms typ)
Built-in OVP/UVP/OCP
Power Good Indicator
Fixed 300kHz VCLK to Support Charge Pump
Individual EN for PWM and LDO
Thermal Shutdown
Simplified Application Circuit
VOUT |
D1 |
D2 |
D3 |
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D4 |
VCP |
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C1 |
C2 |
C3 |
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C4 |
C5 |
VIN |
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VIN |
CLK |
BOOT |
RB |
CIN |
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RT7291A/B |
CB L |
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EN |
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SW |
VOUT |
VLDO |
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LDO |
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CLDO |
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COUT |
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VOUT |
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RBYP |
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PGND |
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VOUT |
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VBYP |
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RPGOOD |
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CBYP |
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PGOOD |
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VCC |
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ENLDO |
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VCC |
CVCC |
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AGND |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS7291A/B-02 September 2015 |
www.richtek.com |
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1 |
Pin Configurations
(TOP VIEW)
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Package Type |
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AGND EN ENLDO VCC BOOT |
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QUF : UQFN-16L 3x3 (FC) (U-Type) |
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Lead Plating System |
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10 |
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G : Green (Halogen Free and Pb Free) |
VIN |
1 |
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Output Voltage |
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SW |
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15 |
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A : 5V |
PGND |
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SW |
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Note : |
B : 5.1V |
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16 |
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SW |
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SW |
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Richtek products are : |
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RoHS compliant and compatible with the current require- |
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VBYP |
PGOOD |
CLK |
LDO |
VOUT |
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ments of IPC/JEDEC J-STD-020. |
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Suitable for use in SnPb or Pb-free soldering processes. |
UQFN-16L 3x3 (FC) |
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RT7291AGQUF |
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RT7291BGQUF |
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39= : Product Code |
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4M= : Product Code |
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39=YM |
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YMDNN : Date Code |
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4M=YM |
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YMDNN : Date Code |
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DNN |
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DNN |
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Pin No. |
Pin Name |
Pin Function |
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1 |
VIN |
Power Input Connect to High-Side MOSFET Drain. |
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2 |
PGND |
Power Ground. |
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Switch Over Source Voltage for VCC. A low pass filter should be connected to |
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VBYP |
AGND, if VBYP is applied. If VBYP is not used, then connect to AGND. Do not |
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connect to VCC pin. |
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4 |
PGOOD |
Open-Drain Power Good Indicator Output. |
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5 |
CLK |
300kHz Clock Output to Drive the External Charge Pump. |
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6 |
LDO |
5V Linear Regulator Output. Decouple with a minimum 4.7 F ceramic capacitor. |
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7 |
VOUT |
Output Voltage Sense Input. An internal discharging circuit is connected to this |
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pin. |
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8, 9, 15, 16 |
SW |
Switch Node. |
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Bootstrap Supply for High-Side Gate Driver. A capacitor is needed to drive the |
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BOOT |
power switch's gate above the supply voltage. It is connected between the SW |
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and BOOT pins to form a floating supply across the power switch driver. |
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5V Linear Regulator Output for Internal Control Circuit. A capacitor (typical 2.2 F) |
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11 |
VCC |
should be connected to AGND. VCC can only supply internal circuits. Do not |
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connect to external loads. |
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12 |
ENLDO |
Enable Control Input for Linear Regulator. This pin is internally pulled up to high by |
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10 A. |
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13 |
EN |
Enable Control Input. Do not leave this pin floating. |
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14 |
AGND |
Analog Ground. |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
DS7291A/B-02 September 2015 |
2 |
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RT7291A/B
Function Block Diagram
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VCC |
VBYP |
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VIN |
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Soft-Start |
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POR & |
VCC |
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BSTREG |
BOOT |
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Reference |
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VOUT |
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Switch-Over |
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VIN |
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VREF |
+ |
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On-Time |
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+ |
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VFB |
- |
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One shot |
Gate |
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SW |
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Min off Time |
Control |
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VCC |
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Logic |
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EN |
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VOUT |
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PGND |
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120% x VREF |
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SW |
+ OCP |
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PGOOD |
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VOC |
- |
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- |
OVP |
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Fault |
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+ |
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- |
POK |
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Logic |
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90% x VREF |
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AGND |
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+ |
60% x VREF |
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UVP |
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- |
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VOUT |
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VCC |
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VOUT |
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CLK |
CLK |
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VCC |
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LDO |
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LDO |
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Generator |
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Control |
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Regulator |
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Switch-Over |
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VIN |
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ENLDO |
LDO |
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Operation
Overall
The RT7291A/B is a synchronous step-down converter with advanced constant on-time control mode. Using the ACOTTM control mode can reduce the output capacitance and provide fast transient response. It can minimize the component size without additional external compensation network.
Internal VCC Regulator
The regulator provides 5V power to supply the internal control circuit. Connecting a 2.2μF ceramic capacitor for decoupling and stability is required.
Soft-Start
In order to prevent the converter output voltage from overshooting during the startup period, the soft-start function is necessary. The soft-start time is internal setting and the duration is around 1.5ms
OCP
The inductor valley current is monitored via the internal switches in cycle-by-cycle. Once the output voltage drops below UV threshold, the device enters latch mode.
Power Good
After soft-start is finished, the power good function will be activated. The PGOOD pin is an open-drain output.
CLK Generator
Provide a 300kHz clock to drive external charge pump.
VCC Switch-Over
The internal regulator output will switch over to VBYP if VBYP level is higher than 4.6V.
LDO
Built-in 5V, 100mALDO with 1% accuracy. The LDO output will switch over to VOUT once PGOOD goes high.
Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS7291A/B-02 September 2015 |
www.richtek.com |
|
3 |
RT7291A/B
Absolute Maximum Ratings (Note 1)
Supply Input Voltage, VIN ---------------------------------------------------------------------------------- |
−0.3V to 27V |
Switch Voltage, SW ----------------------------------------------------------------------------------------- |
− 0.3V to (VIN + 0.3V) |
<30ns ----------------------------------------------------------------------------------------------------------- |
−5V to 28V |
BOOT Switch Voltage --------------------------------------------------------------------------------------- |
(VSW − 0.3V) to (VSW + 6V) |
EN, ENLDO Pin Voltages ---------------------------------------------------------------------------------- |
−0.3V to 27V |
Other I/O Pin Voltages -------------------------------------------------------------------------------------- |
−0.3V to 6V |
Power Dissipation, PD @ TA = 25°C |
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UQFN-16L 3x3 (FC) ------------------------------------------------------------------------------------------ |
1.4W |
Package Thermal Resistance (Note 2) |
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UQFN-16L 3x3 (FC), θJA ------------------------------------------------------------------------------------ |
70°C/W |
UQFN-16L 3x3 (FC), θJC ------------------------------------------------------------------------------------ |
15°C/W |
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------ |
260°C |
Junction Temperature ---------------------------------------------------------------------------------------- |
150°C |
Storage Temperature Range ------------------------------------------------------------------------------- |
−65°C to 150°C |
ESD Susceptibility (Note 3) |
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HBM (Human Body Model) --------------------------------------------------------------------------------- |
2kV |
MM (Machine Model) ---------------------------------------------------------------------------------------- |
200V |
Recommended Operating Conditions |
(Note 4) |
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Supply Input Voltage, VIN |
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5V to 23V |
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Junction Temperature Range ------------------------------------------------------------------------------- |
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−40°C to 125°C |
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Ambient Temperature Range ------------------------------------------------------------------------------- |
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−40°C to 85°C |
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Electrical Characteristics |
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(VIN = 12V, TA = 25°C, unless otherwise specified) |
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Parameter |
Symbol |
Test Conditions |
Min |
Typ |
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Max |
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Unit |
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Supply Current |
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Shutdown Current |
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VEN = VENLDO = 0V |
-- |
2.5 |
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5 |
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A |
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Quiescent Current |
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VEN = 2V, VENLDO = 2V, No Switching |
-- |
100 |
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130 |
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A |
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Standby Current |
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VEN = 0V, VENLDO = 2V, LDO Load |
-- |
35 |
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45 |
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A |
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Current = 0A |
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Switch On-Resistance |
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Switch On-Resistance |
RDS(ON)_H |
VBOOT – VSW = 5V |
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31 |
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-- |
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m |
RDS(ON)_L |
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-- |
20 |
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-- |
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Current Limit |
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Current Limit |
IOC |
Valley current of low-side switch |
7.6 |
-- |
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11.4 |
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A |
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Switching Frequency and Minimum Off Timer |
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Switching Frequency |
fSW |
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450 |
500 |
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550 |
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kHz |
Minimum Off-Time |
TOFF |
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-- |
200 |
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-- |
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Protections |
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OVP Trip Threshold |
VOVP |
With respect to output voltage |
115 |
120 |
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125 |
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% |
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OVP Propagation Delay |
TOVPDLY |
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-- |
5 |
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-- |
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s |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
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www.richtek.com |
DS7291A/B-02 September 2015 |
4 |
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RT7291A/B
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
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UVP Trip Threshold |
VUVP |
With respect to output voltage |
55 |
60 |
65 |
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% |
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UVP Propagation Delay |
TUVPDLY |
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-- |
5 |
-- |
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Reference and Soft-Start |
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Output Voltage Valley |
VOUT |
RT7291A |
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4.95 |
5 |
5.05 |
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RT7291B |
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5.049 |
5.1 |
5.151 |
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Soft-Start Time |
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TSS |
From EN high to PGOOD high |
1 |
1.5 |
2 |
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Enable and UVLO |
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EN Input High Voltage |
VENH |
RT7291A |
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1.25 |
1.35 |
1.45 |
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RT7291B |
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1.3 |
1.4 |
1.5 |
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EN Hysteresis |
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VENHYS |
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-- |
200 |
-- |
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mV |
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EN Input Current |
IEN |
VEN = 2V |
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1 |
-- |
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A |
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VEN = 0V |
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-- |
0 |
-- |
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VCC UVLO Rising |
VCCUVLO |
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-- |
4.2 |
-- |
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V |
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VCC UVLO Hysteresis |
VCCHYS |
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-- |
400 |
-- |
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mV |
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CLK Output |
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CLK Output |
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High-Level |
VCLKH |
IVCLK = 10mA |
RT7291A |
-- |
-- |
5.05 |
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RT7291B |
-- |
-- |
5.151 |
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V |
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Voltage |
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Low-Level |
VCLKL |
IVCLK = 10mA |
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0 |
0.1 |
0.2 |
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CLK Frequency |
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fCLK |
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-- |
300 |
-- |
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kHz |
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LDO Regulator |
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LDO Regulator |
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VLDO |
RT7291A |
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4.95 |
5 |
5.05 |
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V |
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RT7291B |
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5.049 |
5.1 |
5.151 |
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EN = GND, |
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1 |
-- |
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LDO Load Current = 5mA |
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LDO Load Regulation |
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% |
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EN = GND, |
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-- |
5 |
-- |
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LDO Load Current = 100mA |
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Switch On-Resistance |
RSW |
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-- |
3 |
5 |
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VCC Regulator |
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VCC Regulator |
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VVCC |
RT7291A |
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4.805 |
5 |
5.295 |
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V |
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RT7291B |
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4.905 |
5.1 |
5.395 |
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VCC Switch Over Threshold to |
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VBYP Rising |
RT7291A |
4.45 |
4.6 |
4.75 |
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V |
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VBYP |
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Edge |
RT7291B |
4.542 |
4.692 |
4.842 |
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VCC Switch Over Hysteresis |
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VBYP Falling Edge |
-- |
200 |
-- |
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mV |
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Switch Over On-Resistance |
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-- |
3 |
5 |
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Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
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DS7291A/B-02 September 2015 |
www.richtek.com |
|
5 |
RT7291A/B
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
Power Good Indicator |
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PGOOD Threshold From Lower |
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VOUT Rising |
85 |
90 |
95 |
% |
PGOOD Low Hysteresis |
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VOUT Falling |
-- |
10 |
-- |
% |
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PGOOD Low to High Delay |
TPGDLY |
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-- |
0.5 |
-- |
ms |
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PGOOD Sink Current Capability |
VPGSINK |
Sink 4mA |
-- |
-- |
0.4 |
V |
|
|
|
|
|
|
|
PGOOD Leakage Current |
IPGLEAK |
VPGOOD = 5V |
-- |
-- |
100 |
nA |
|
|
|
|
|
|
|
Thermal Shutdown |
|
|
|
|
|
|
|
|
|
|
|
|
|
Thermal Shutdown Threshold |
TSD |
|
135 |
150 |
-- |
°C |
|
|
|
|
|
|
|
Thermal Shutdown Hysteresis |
|
|
-- |
25 |
-- |
°C |
|
|
|
|
|
|
|
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and 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 may affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright ©2014 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
DS7291A/B-02 September 2015 |
6 |
|
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