FINTEK F72815SG Synchronous buck pwm dc-dc controller with external reference voltage input Datasheet

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
Date
0.10
Jun, 2006
0.11
Dec, 2006
0.12
0.13
Jul, 2007
Jul, 2007
Page
Revision History
Preliminary version
8
Adjust Vref description
11
Add application circuit
8
Adjustable input reference voltage description
9
Add Typical characteristics
13
Update company address
2
Pin configuration
Shut down level: 0.15V
0.14
Aug, 2007
2
Pin description, VREF
4
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.
Aug, 2007
V0.14
F72815
Table of Content
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
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
Aug, 2007
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
„
F72815
±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)
-1-
Aug, 2007
V0.14
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
UGATE
3
VREF
4
LGATE
5
VCC
6
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
F72815
PHASE
Connect this pin to the source of the upper MOSFET and the drain of the lower MOSFET.
-2-
Aug, 2007
V0.14
F72815
9
GND
Power ground pin for the chip
5. Electrical Characteristic
Absolute Maximum Ratings
PARAMETER
SYMBOL
RATINGS
UNIT
VCC
15
V
VPHASE – GND
15
V
VBOOT - VPHASE
15
V
VBOOT - GND
VCC + 15
V
PWM controller outputs
UGATE
(VPHASE - 0.3) to (VBOOT + 0.3)
V
PWM controller outputs
LGATE
(GND - 0.3) to (VCC + 0.3)
V
Feedback voltages
FB
(GND - 0.3) ~ 7
V
ESD classification
HBM
2
kV
Tj
150
°C
TSTO
-65 ~ 150
°C
260
°C
IC supply voltage
PHASE to GND
BOOT to PHASE
BOOT to GND
※ Maximum junction temperature (plastic package)
※ Maximum storage temperature
※ Maximum lead temperature (soldering 10s)
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
SYMBOL
RATINGS
UNIT
Supply Voltage
VCC
5 ± 5%,12 ± 10%
V
Ambient Temperature
0 ~ 70
°C
Junction Temperature
0 ~ 125
°C
Package thermal information
PARAMETER
Thermal resistance junction-ambient
SYMBOL
SOIC
UNIT
Rth_ja
133(R), 160(O)
°C/W
DC and AC electrical characteristics (VCC = 12V, TA = 25℃)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN.
TYP.
MAX.
UNIT
6
15
mA
VCC SUPPLY CURRENT/Regulated Voltage
Nominal supply current 5VCC
F72815
ICC
UGATE, LGATE and DRIVE2 open
-3-
Aug, 2007
V0.14
F72815
PARAMETER
SYMBOL
TEST CONDITIONS
MIN.
TYP.
MAX.
UNIT
Rising VCC threshold
4.1
4.4
V
Falling VCC threshold
3.6
3.75
V
300
350
kHz
POWER-ON RESET
OSCILLATOR AND Protection
Free running frequency
※ Ramp Amplitude
FOSC
250
1.5
△VOSC
FB Under Voltage Trip
0.48
0.5
0.52
V
IOCSET
35
40
45
uA
Soft-start interval
TSS
1
3
6
ms
Dead time
TDT
100
ns
OCSET Current Source
FB Falling
VP-P
2V to 2V
20
PWM CONTROLLER GATE DRIVERS
Upper Drive Source
RUGATE
VDS = 1V, VGS = 12V,
5
10
Ω
Upper Drive Sink
RUGATE
VDS = 1V, VGS = 12V
4
8
Ω
Lower Drive Source
RLGATE
VDS = 1V, VGS = 12V
4
8
Ω
Lower Drive Sink
RLGATE
VDS = 1V, VGS = 12V
3
5
Ω
Error Amplifier
※ E/A Transconductance
gm
2.5
※ DC Gain
A0
85
*
u A/V
dB
※: Design Guarantee
F72815
-4-
Aug, 2007
V0.14
F72815
6. Block Diagram
VDDA
V3VAA
0.4V
Reference
Voltage
Bias & Regulator
(VDD & V3VAA)
OC
Power On
Reset
OCSET
0.1V
0.8V
VREF
40uA
Comp
SD
TRAP_SEL
0.6V
UVP
Comp
UV
Control
Logic
1.5V
PH_M
Comp
VDD
BOOT
GM
FB
Comp
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
F72815
-5-
Aug, 2007
V0.14
F72815
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
BOOT
VCC
C BOOT
UGATE
Q1
PHASE
LGATE
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.
F72815
-6-
Aug, 2007
V0.14
F72815
VCC = 12V
12V
6V
VCC = 5V
VOUT
0V
TIME
3mS
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 40μA 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
0V
VOUT
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.
F72815
-7-
Aug, 2007
V0.14
F72815
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.
VCC
5V
PWOK
VOUT
0V
1
2
3
4
5
6
7
TIME (ms)
UGATE
Figure 5
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.
F72815
-8-
Aug, 2007
V0.14
F72815
8. Typical Characteristic
Efficiency V.S. Output Current
95
90
90
Efficiency (%)
95
85
80
75
85
80
75
70
70
0
5
10
15
20
0
5
10
Output Current (A)
15
20
Output Current (A)
VCC=12V, VIN=5V, VOUT=2.5V
VCC=5V, VIN=5V, VOUT=2.5V
POR V.S. Temperature
Frequency V.S. Temperature
4.6
350
Rising
330
Voltage (V)
Frequency (KHz)
Efficiency (%)
Efficiency V.S. Output Current
310
290
4.2
Falling
3.8
270
3.4
250
-10
5
20
35
50
65
80
95
110
5
20
35
50
65
80
95
Temperature (℃)
Temperature (℃)
F72815
-10
-9-
Aug, 2007
V0.14
110
F72815
Dead Time (Rising)
Dead Time (Falling)
UGATE
UGATE
LGATE
LGATE
Time 20.0ns/Div.
Time 20.0ns/Div.
VCC=12V, VIN=5V, IOUT=2.5A
Under Voltage Protection
UGATE
UGATE
FB
FB
FB > 0.5V
F72815
FB < 0.5V
-10-
Aug, 2007
V0.14
F72815
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
F72815
-11-
Aug, 2007
V0.14
F72815
9. Ordering Information
F72815
Part Number
Package Type
Production Flow
F72815SG
8-SOP (Green Package)
Commercial, 0°C to +70°C
-12-
Aug, 2007
V0.14
F72815
10. Package Dimensions (8-SOP/150 mil)
8
5
c
E
HE
L
4
1
0.25
D
O
A
Y
e
SEATING PLANE
GAUGE PLANE
A1
b
Control demensions are in milmeters .
SYMBOL
A
A1
b
c
E
D
e
HE
Y
L
θ
F72815
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
-13-
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
Aug, 2007
V0.14
F72815
Feature Integration Technology Inc.
Headquarters
Taipei Office
3F-7, No 36, Tai Yuan St.,
Bldg. K4, 7F, No.700, Chung Cheng Rd.,
Chupei City, Hsinchu, Taiwan 302, R.O.C.
Chungho City, Taipei, Taiwan 235, R.O.C.
TEL : 886-3-5600168
TEL : 866-2-8227-8027
FAX : 886-3-5600166
FAX : 866-2-8227-8037
www: http://www.fintek.com.tw
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
F72815
-14-
Aug, 2007
V0.14
F72815
11. Application Circuit
15
Similar pages