View F72814_4419760.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

F72814
F72814 Datasheet
Synchronous Buck PWM DC-DC Controller
Release Date: July, 2007 Version: V0.23P
V0.23P
F72814
F72814 Datasheet Revision History
Version 0.20P 0.21P 0.22P 0.23P Apr, 2006 May,2006 Jul, 2007 3 4 8 11 Re-compose Remove free run frequency Add dead time measurement loading Add typical characteristic diagram Update company address Date Page Revision History Preliminary version
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.
V0.23P
F72814
Table of Content
General Description ........................................................................................................................1 Feature List .....................................................................................................................................1 Pin Configuration............................................................................................................................2 Pin Description................................................................................................................................2 Electrical Characteristic ..................................................................................................................2 Block Diagram ................................................................................................................................4 Function Description.......................................................................................................................5 7.1 Bootstrap Operation ....................................................................................................................5 7.2 Power On Reset...........................................................................................................................5 7.3 Soft-Start .....................................................................................................................................6 7.4 Over-current Protection ..............................................................................................................6 7.5 Under-voltage Protection ............................................................................................................6 7.6 Shutdown ....................................................................................................................................7 7.7 VIN Sense ...................................................................................................................................7 8. Typical Characteristic .................................................................................................................8 9. Ordering Information ......................................................................................................................9 10. Package Dimensions (8-SOP/150 mil) .........................................................................................11 11. Application Circuit........................................................................................................................12 1. 2. 3. 4. 5. 6. 7.
V0.23P
F72814 1. General Description
The F72814 is a high-efficiency synchronous buck PWM controller that 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 0~80% 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 8-SOP package (150 mil)
F72814
-1-
V0.23P
F72814 3. Pin Configuration
BOOT UGATE GND LGATE 1 2 3 4 8 7 6 5 PHASE OCSET FB VCC
F72814
4. Pin Description
Pin No 1 Pin Name BOOT Description Bootstrap supply pin for the upper gate driver. Connect the bootstrap capacitor between BOOT pin and the PHASE pin. The bootstrap capacitor provides the charge to turn on the upper MOSFET. 2 3 4 5 6 UGATE GND LGATE VCC FB Higher gate drive output. Connect this pin to gate of the high side MOSFET Power ground pin for the chip 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. 7 OCSET/SD This is multi-function pin. Connecting a resistor ROCSET from this pin to PHASE, and an internal 40uA current source from VCC. OCSET voltage can sense loading status when low side MOSFET turn on. When OCSET voltage is under 0.1V, 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.
5. Electrical Characteristic
Absolute Maximum Ratings
PARAMETER
IC supply voltage PHASE to GND BOOT to PHASE
SYMBOL
VCC VPHASE - GND VBOOT - VPHASE
RATINGS
15 15 15
UNIT
V V V
F72814
-2-
V0.23P
F72814
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) VBOOT - GND UGATE LGATE FB HBM Tj TSTO 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 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
160
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 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 IOCSET TSS FOSC VOSC FB Falling 0.48 35 1 250 300 1.5 0.5 40 3 0.52 45 6 350 kHz VP-P V uA ms 4.1 3.6 4.4 3.75 V V ICC UGATE, LGATE and DRIVE2 open 6 15 mA
F72814
-3-
V0.23P
F72814
PARAMETER
Dead time REFERENCE VOLTAGE Reference voltage 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 1.67 85
*
SYMBOL
TDT
TEST CONDITIONS
2V to 2V, Loading =2A
MIN.
10
TYP.
MAX.
100
UNIT
ns
VREF
VCC=5V, T= 25
0.784
0.8
0.816
V
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
6. Block Diagram
VDDA V3VAA
0.4V Reference Voltage Bias & Regulator (VDD & V3VAA) Power On Reset OC Comp 0.15V SD UVP UV Comp
40uA
OCSET
0.6V
Control Logic VDD
1.5V PH_M Comp
0.8V GM
BOOT
Comp
FB
UGATE PHASE
VDDA
LGATE
300KHz Tri-OSC
GND
Figure 1: Block Diagram
F72814
-4-
V0.23P
F72814 7. Function Description
The F72814 is a single PWM DC-DC converter controller for application which requires high current such as motherboard, graphic card etc. The F72814 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 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 F72814 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 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 F72814S 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.
F72814
-5-
V0.23P
F72814
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.
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.
F72814
-6-
V0.23P
F72814
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.
7.6 Shutdown
It can shut down the F72814 PWM controller to pull low the OCSET pin under 0.15V.
7.7 VIN Sense
The F72814 Vin power is sensed by OCSET voltage at first soft start event, when soft start event occurs. UGATE pulse will be enabled, and the F72814 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
F72814
-7-
V0.23P
F72814 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
Reference Voltage V.S. Temperature 0.806 Reference Voltage (V) 0.802 0.798 0.794 0.79 0.786 -10 5 20 35 50 65 80 95 110 Temperature ()
Frequency V.S. Temperature 350 330 310 290 270 250 -10 5 20 35 50 65 80 95 110 Temperature ()
POR V.S. Temperature 4.6
Rising
Voltage (V)
4.2
3.8
Falling
3.4 -10 5 20 35 50 65 80 95 110 Temperature ()
F72814
Frequency (KHz)
-8-
V0.23P
F72814
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
F72814
-9-
V0.23P
F72814
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
9. Ordering Information
Part Number F72814SG Package Type 8-SOP (Green Package) Production Flow Commercial, 0C to +70C
F72814
-10-
V0.23P
F72814 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
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
F72814
-11-
V0.23P
F72814S 11. Application Circuit
VIN(5V/12V)
L1 1u
VCC(5V/12V) C1 1u C2 470u C3 470u D1 DIODE
C4 0.1u R3 20k R1 2.2
VCC1P8V
Q1 MOSFET_EN_GDS L2 3.3u
R2
2.2 U1 1 2 3 4 BOOT UGATE GND LGATE F72814SG PHASE OCSET FB VCC 8 7 6 5
C5 1000u
C6 1000u
C7 1000u
C8 1u
Q2 MOSFET_EN_GDS
R4
2.2
C9 1u
R5 R6 200
2.5k C10 0.1u
FB
R7 2k
12
F72814S
13

▲Up To Search▲

Price & Availability of F72814

	To Download F72814 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .