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F72815
F72815 Datasheet
Synchronous Buck PWM DC-DC Controller with External Reference Voltage Input
Release Date: Aug, 2007 Version: V0.14
Aug, 2007
V0.14
F72815
F72815 Datasheet Revision History
Version 0.10 0.11 Date Jun, 2006 Dec, 2006 8 11 0.12 Jul, 2007 8 9 13 0.13 Jul, 2007 2 Page Revision History Preliminary version Adjust Vref description Add application circuit Adjustable input reference voltage description Add Typical characteristics Update company address Pin configuration Shut down level: 0.15V 0.14 Aug, 2007 2 4 Pin description, VREF Power Good maximum value: 4.4V Feedback under voltage trip: 0.5V Remove free running frequency test mode Remove reference voltage 14 Add SOP-8 EP dimension
Please note that all data and specifications are subject to change without notice. All the trade marks of products and companies mentioned in this data sheet belong to their respective owners.
LIFE SUPPORT APPLICATIONS These products are not designed for use in life support appliances, devices, or systems where malfunction of these products can reasonably be expected to result in personal injury. Customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Fintek for any damages resulting from such improper use or sales.
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V0.14
F72815 Table of Content
1. 2. 3. 4. 5. 6. 7. General Description ........................................................................................................ 1 Feature List..................................................................................................................... 1 Pin Configuration ............................................................................................................ 2 Pin Description ............................................................................................................... 2 Electrical Characteristic .................................................................................................. 3 Block Diagram ................................................................................................................ 5 Function Description ....................................................................................................... 5 7.1 Bootstrap Operation .................................................................................................... 6 7.2 Power On Reset.......................................................................................................... 6 7.3 Soft-Start ..................................................................................................................... 6 7.4 Over-current Protection............................................................................................... 7 7.5 Under-voltage Protection ............................................................................................ 7 7.6 Shutdown .................................................................................................................... 8 7.7 VIN Sense ................................................................................................................... 8 7.8 Adjustable Reference Voltage Input ............................................................................ 8 Typical Characteristic...................................................................................................... 9 Ordering Information..................................................................................................... 12 Package Dimensions (8-SOP/150 mil) ......................................................................... 13 Application Circuit ......................................................................................................... 15
8. 9. 10. 11.
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V0.14
F72815 1. General Description
The F72815 is a high-efficiency synchronous buck PWM controller with an adjustable reference voltage input to provide an option for over voltage function, which generates logic-supply voltages in PC based systems. This high-performance , single output device includes internal soft-start, frequency-compensation networks, power good signal with delay, and integrates all of the control, output adjustment, monitoring and protection functions into a single package. This device operates at a fixed frequency, 300K Hz and provides an optimum compromise between efficiency, external component size, and cost. Adjustable over-current protection (OCP) monitors the voltage drop across the RDS (ON) of the lower MOSFET for synchronous buck PWM DC-DC controller. The over-current function cycles the soft-start in 4-times hiccup mode to provide fault protection, and in a routine hiccup mode for under-voltage protection.
2. Feature List
Provides one synchronous rectified buck DC-DC PWM controller Fast transient response (high bandwidth error amplifier; full 0~100% duty cycle) Fixed operation frequency : 300KHz Single loop voltage-mode control Few external components Output range adjustable down to 0.8V Operates under 5V to 12V input Drives all low cost N-channel MOSFETs Uses MOSFET RDS(ON) as over current monitor, and no current sense resistor is required 0.8V internal reference voltage 2% accuracy over line, load and temperature Internal soft-start (typically 3 ms) Internal loop compensation Under voltage fault monitoring and protection Over voltage protection Adaptive Non-Overlapping Gate Driver Adjustable Reference Voltage Input for Over Voltage Function, Input Range: 0.78~1.2V, Enable Level: under 1.5V 8-SOP package (150 mil)
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F72815 3. Pin Configuration
GND 9
4. Pin Description
Pin No Pin Name Description Bootstrap supply pin for the upper gate driver. Connect the bootstrap capacitor between 1 BOOT BOOT pin and the PHASE pin. The bootstrap capacitor provides the charge to turn on the upper MOSFET. 2 3 4 5 6 UGATE VREF LGATE VCC FB Higher gate drive output. Connect this pin to gate of the high side MOSFET Reference voltage input. The input range is 0.6V~1.8V. Lower gate drive output. Connect this pin to gate of the low side MOSFET IC supply voltage. This voltage is monitored for power-on-reset purpose. Inverting input of the error amplifier used to compensate the feedback loop of the PWM controller. This is multi-function pin. Connecting a resistor ROCSET from this pin to PHASE, and an 7 internal 40uA current source from VCC. OCSET voltage can sense loading status when OCSET/SD low side MOSFET turn on. When OCSET voltage is under 0.15V, shut down (SD) function will be enabled. 8 PHASE Connect this pin to the source of the upper MOSFET and the drain of the lower MOSFET.
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9 GND Power ground pin for the chip
5. Electrical Characteristic
Absolute Maximum Ratings
PARAMETER
IC supply voltage PHASE to GND BOOT to PHASE BOOT to GND PWM controller outputs PWM controller outputs Feedback voltages ESD classification Maximum junction temperature (plastic package) Maximum storage temperature Maximum lead temperature (soldering 10s)
SYMBOL
VCC VPHASE - GND VBOOT - VPHASE VBOOT - GND UGATE LGATE FB HBM Tj TSTO
RATINGS
15 15 15 VCC + 15 (VPHASE - 0.3) to (VBOOT + 0.3) (GND - 0.3) to (VCC + 0.3) (GND - 0.3) ~ 7 2 150 -65 ~ 150 260
UNIT
V V V V V V V kV C C C
Note: If ICs are stressed beyond the limits listed in the "absolute maximum ratings", they may be permanently destroyed. These are stress ratings only and functional operations of the device at these or any other condition beyond those indicated under "recommended operating conditions" are not implied. Exposure to absolute maximum rated conditions for extended periods may affect device reliability.
Recommended Operating Conditions
PARAMETER Supply Voltage Ambient Temperature Junction Temperature SYMBOL VCC RATINGS 5 5%,12 10% 0 ~ 70 0 ~ 125 UNIT V C C
Package thermal information
PARAMETER
Thermal resistance junction-ambient
SYMBOL
Rth_ja
SOIC
133(R), 160(O)
UNIT
C/W
DC and AC electrical characteristics (VCC = 12V, TA = 25)
PARAMETER SYMBOL TEST CONDITIONS MIN. TYP. MAX. UNIT
VCC SUPPLY CURRENT/Regulated Voltage Nominal supply current 5VCC ICC UGATE, LGATE and DRIVE2 open 6 15 mA
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PARAMETER
POWER-ON RESET Rising VCC threshold Falling VCC threshold OSCILLATOR AND Protection Free running frequency Ramp Amplitude FB Under Voltage Trip OCSET Current Source Soft-start interval Dead time PWM CONTROLLER GATE DRIVERS Upper Drive Source Upper Drive Sink Lower Drive Source Lower Drive Sink Error Amplifier E/A Transconductance DC Gain gm A0 2.5 85
*
SYMBOL
TEST CONDITIONS
MIN.
TYP.
MAX.
UNIT
4.1 3.6
4.4 3.75
V V
FOSC VOSC FB Falling IOCSET TSS TDT 2V to 2V
250
300 1.5
350
kHz VP-P
0.48 35 1 20
0.5 40 3
0.52 45 6 100
V uA ms ns
RUGATE RUGATE RLGATE RLGATE
VDS = 1V, VGS = 12V, VDS = 1V, VGS = 12V VDS = 1V, VGS = 12V VDS = 1V, VGS = 12V
5 4 4 3
10 8 8 5

u A/V dB
: Design Guarantee
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F72815 6. Block Diagram
VDDA V3VAA
0.4V Reference Voltage 0.8V Bias & Regulator (VDD & V3VAA) Power On Reset OC Comp 0.1V SD TRAP_SEL 0.6V UVP UV Comp
40uA
OCSET
VREF
Control Logic VDD
1.5V PH_M Comp
GM
BOOT
Comp
FB
UGATE PHASE
VDDA
LGATE
300KHz Tri-OSC
GND
Figure 1: Block Diagram
7. Function Description
The F72815 is a single PWM DC-DC converter controller for application which requires high current such as motherboard, graphic card etc. The F72815 uses voltage mode PWM controller with fast transient response (driving two external N-channel MOSFETs in a synchronous rectified buck converter topology) and integrates some functions such as adjustable reference voltage input for overclock, soft-start, over current and short circuit protections etc. Over current protection is achieved by monitoring the PHASE negative voltage when heavy loading without the need of a current sensing resistor and short circuit condition is detected through FB pin. If over current condition occurs, the F72815 will initiate the soft start cycle. After two cycles and the fault condition persist, the controller will go into shut down status. In shut down status, both gate drive signals will be low. To restart the controller, either recycling VCC supply or momentarily pulling the OCSET pin below 0.15V. If under voltage condition occurs, it will keep hiccup mode in
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this event.
7.1 Bootstrap Operation
In the single power supply system, UGATE is powered by an external bootstrap circuit as Figure 3. The Boot capacitor, CBOOT is charged and generated a floating reference voltage at PHASE pin. Typically, a 0.1uF CBOOT is enough for the most of applications. The CBOOT capacitor is refreshed and charged to a voltage of "VCC - Diode Drop" while low side power MOS turns on.
5V to 12V 3.3V/5V/12V VCC BOOT C BOOT UGATE PHASE LGATE Q1 VOUT Q2
Fig 2. Power Supply Operation.
7.2 Power On Reset
The F72815 Power-on-reset monitors VCC supply voltage and input voltage at OCSET pin. POR level is 4.1V with 0.5V hysteresis at VCC voltage and 0.15V at OCSET voltage, The POR function initiates soft-start operation and resets control logic after the supply voltages exceeds its POR threshold voltage.
7.3 Soft-Start
When the POR function initiates the digital soft-start sequence, PWM error amplifier reference inputs are forced to track a voltage level proportional to the soft-start voltage. As the soft-start voltage slews up, the PWM comparator regulates the output relative to the tracked soft-start voltage, and slowly charges the output capacitor(s). In the digital soft-start sequence initiated by the POR function, the soft start function is used to prevent surge current from power supply input during power on. The soft start duration is 3mS in typical case.
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12V VCC = 12V
6V
VCC = 5V VOUT
0V
3mS
TIME
Figure 3 : Soft start duration
7.4 Over-current Protection
To sense the low-side MOSFET's RDS (ON) to set over-current trip point. Connecting a resistor (ROCSET) from this pin to PHASE to set the over-current trip point, ROCSET, an internal 40A current source, and the lower MOSFET on resistance, RDS (ON), sets the converter over-current trip point (IOCSET) according to the following equation:
7.5 Under-voltage Protection
If the FB voltage drops under 0.5V, a fault signal is generated. When under voltage condition occurs, it will keep hiccup mode in this event.
3V
1.5V
VOUT
0V
t0
tss
2tss
3tss
4tss
TIME
Figure 4 : Under voltage event occur
But UV_FB has some differences from OC, it always trigger VIN power sensing after 4 times hiccup.
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7.6 Shutdown
It can shut down the F72815 PWM controller to pull low the OCSET pin under 0.15V.
7.7 VIN Sense
The F72815 Vin power is sensed by OCSET voltage at first soft start event, when soft start event occurs. UGATE pulse will be enabled, and the F72815 detects the first ten UGATE high pulse. If there are four PH_M pulse during the ten pulse period, it means Vin ready, If Vin is ready, VOUT will be ramped up in next soft start event. Otherwise, we will check Vin voltage at the next soft start event.
5V
VCC
PWOK
VOUT
0V 1 UGATE
Figure 5
2
3
4
5
6
7
TIME (ms)
7.8 Adjustable Reference Voltage Input
The F72815 supports external reference voltage input to replace the internal feedback reference voltage. The output voltage can be adjusted according to the different external reference voltage. The high level of input reference voltage is over 0.6V, and then the F72815 will be active to track the reference voltage. The maximum of the reference voltage input is 1.8V.
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F72815 8. Typical Characteristic
Efficiency V.S. Output Current 95 90 Efficiency (%) 85 80 75 70 0 5 10 Output Current (A) 15 20
Efficiency (%) 95 90 85 80 75 70 0 5 10 Output Current (A) 15 20 Efficiency V.S. Output Current
VCC=12V, VIN=5V, VOUT=2.5V
VCC=5V, VIN=5V, VOUT=2.5V
POR V.S. Temperature
Frequency V.S. Temperature 350
4.6
Rising
Voltage (V)
Frequency (KHz)
330 310 290 270 250 -10 5 20 35 50 65 80 95 110 Temperature ()
4.2
Falling
3.8
3.4 -10 5 20 35 50 65 80 95 110 Temperature ()
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Dead Time (Rising) Dead Time (Falling)
UGATE UGATE
LGATE
LGATE
Time 20.0ns/Div. VCC=12V, VIN=5V, IOUT=2.5A
Time 20.0ns/Div.
Under Voltage Protection
UGATE UGATE
FB
FB
FB > 0.5V
FB < 0.5V
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Transient Response Time Rising
UGATE, 20.0V/Div.
VOUT, 100mV/Div.
IOUT, 5.0A/Div
VCC=5V VIN=5V IOUT=0-15A Falling
UGATE, 20.0V/Div.
VOUT, 100mV/Div.
IOUT, 5.0A/Div
VCC=5V VIN=5V IOUT=15-0A * The external reference input is 0.8V in all test conditions
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F72815 9. Ordering Information
Part Number F72815SG Package Type 8-SOP (Green Package) Production Flow Commercial, 0C to +70C
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F72815 10. Package Dimensions (8-SOP/150 mil)
8 5
c
E
HE
L
1
D
4
0.25 O
A Y SEATING PLANE b e A1 GAUGE PLANE
Control demensions are in milmeters .
SYMBOL A A1 b c E D e HE Y L DIMENSION IN MM MIN. MAX. 1.35 1.75 0.10 0.25 0.33 0.51 0.19 0.25 3.80 4.00 4.80 5.00 1.27 BSC 6.20 5.80 0.10 0.40 1.27 0 10 DIMENSION IN INCH MIN. MAX. 0.053 0.069 0.010 0.004 0.013 0.020 0.008 0.010 0.150 0.157 0.188 0.196 0.050 BSC 0.228 0.016 0 0.244 0.004 0.050 10
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Feature Integration Technology Inc.
Headquarters 3F-7, No 36, Tai Yuan St., Chupei City, Hsinchu, Taiwan 302, R.O.C. TEL : 886-3-5600168 FAX : 886-3-5600166 www: http://www.fintek.com.tw Taipei Office Bldg. K4, 7F, No.700, Chung Cheng Rd., Chungho City, Taipei, Taiwan 235, R.O.C. TEL : 866-2-8227-8027 FAX : 866-2-8227-8037
Please note that all datasheet and specifications are subject to change without notice. All the trade marks of products and companies mentioned in this datasheet belong to their respective owner
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F72815 11. Application Circuit
15

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