SGS Thomson Microelectronics L6727, L6727TR Datasheet
Feature
■ Flexible power supply from 5V to 12V
■ Power conversion input as low as 1.5V
■ 1% output voltage accuracy
■ High-current integrated drivers
■ Adjustable output voltage
■ 0.8V internal reference
■ Simple voltage mode control loop
■ Sensorless and programmable OCP across
Low-Side R
■
Oscillator internally fixed at 300kHz
■ Internal Soft-Start
■ LS-LESS to manage pre-bias start-up
■ Disable function
■ OV / UV protection
■ FB disconnection protection
■ SO-8 package
dsON
Applications
L6727
Single phase PWM controller
SO-8
Description
L6727 is a single-phase step-down controller with
integrated high-current drivers that provides
complete control logic, protections and reference
voltage to realize in an easy and simple way
general DC-DC converters by using a compact
SO-8 package.
Device flexibility allows managing conversions
with power input V
supply voltage in the range of 5V to 12V.
L6727 provides simple control loop with voltagemode error-amplifier. The integrated 0.8V
reference allows regulating output voltages with
±1% accuracy over line and temperature
variations. Oscillator is internally fixed to 300kHz.
as low as 1.5V and device
IN
■ Subsystem power supply (MCH, IOCH, PCI...)
■ Memory and termination supply
■ CPU & DSP power supply
■ Distributed power supply
■ General DC / DC converters
L6727 provides programmable over current
protection as well as over and under voltage
protection. Current information is monitored
across the Low-Side mosfet R
saving the use
dsON
of expensive and space-consuming sense
resistors while output voltage is monitored
through FB pin.
FB disconnection protection prevents excessive
and dangerous output voltages in case of floating
FB pin.
Table 1. Device summary
Part Number Package Packaging
L6727 SO-8 Tube
L6727TR SO-8 Tape & Reel
June 2007 Rev 3 1/22
www.st.com
1
Contents L6727
Contents
1 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 4
1.1 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Pins description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 Driver section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6 Soft Start and Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 Low-Side-Less Start up (LSLess) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.2 Enable / Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7 Over current protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1 Over current threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8 Output voltage monitor and protections . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1 Under voltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2 Over voltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.3 Feedback disconnection protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.4 Under voltage lock out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2/22
L6727 Contents
9 Application details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1 Output voltage selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.2 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.3 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.4 Embedding L6727-based VRs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3/22
Typical application circuit and block diagram L6727
1 Typical application circuit and block diagram
1.1 Application circuit
Figure 1. Typical application circuit
VCC = 5V to 12V
VIN = 1.5V to 19V (**)
C
DEC
R
C
C
P
R
OS
R
R
L6727 Reference Schematic
(*) R
OCSET
(**) Up to 12V with Vcc > 5V
1.2 Block diagram
Figure 2. Block diagram
VCC
GND
5
UGATE
PHASE
L6727
3
OCSET
(*)
7
COMP /
DIS / OC
F
F
6
FB
FB
not to be connected when VCC > 5V
VCC
BOOT
LGATE
D
R
D
1
C
BOOT
2
R
8
4
gHS
R
gLS
HS
LS
C
HF
L
R
SN
C
SN
C
BULK
Vout
C
OUT
LOAD
CONTROL LOGIC
& PROTECTIONS
OCSET
I
300 kHz
OSCILLATOR
L6727
ERROR
AMPLIFIER
COMP
/ DIS / OC
4/22
Vout Monitor
DISABLE
+
-
FB
CURRENT READ
& OCP
CROSS CONDUCTION
ADAPTIVE ANTI
PWM
0.8V
HS
VCC
LS
BOOT
UGATE
PHASE
LGATE
GND
L6727 Pins description and connection diagrams
2 Pins description and connection diagrams
Figure 3. Pins connection (top view)
BOOT
UGATE
LGATE
2.1 Pin descriptions
Table 2. Pins descriptions
Pin # Name Function
1BOOT
2 UGATE HS Driver Output. Connect to HS mosfet gate.
3GND
4 LGATE LS Driver Output. Connect to LS mosfet gate.
5VCC
1
2
L6727
GND
HS Driver Supply.
Connect through a capacitor (100nF) to the floating node (LS-Drain) pin
and provide necessary bootstrap diode from VCC.
All internal references, logic and drivers are connected to this pin.
Connect to the PCB ground plane.
Device and LS Driver power supply.
Operative range from 4.1V to 13.2V. Filter with at least 1µF MLCC to GND.
3
4
8
PHASE
7
COMP / DIS / OC
6
FB
5
VCC
Error Amplifier Inverting Input.
6FB
COMP / DIS
7
8 PHASE
/ OC
Connect with a resistor R
resistor R
reference.
COMP. Error Amplifier Output. Connect with an R
compensate the control-loop.
DIS. The device can be disabled by forcing this pin lower than 0.5V(typ). To
disable the device, the external pull-down need to overcome 10mA of
COMP output current for about 15µs. Once disabled, COMP output current
drops to 20µA.
OC. Over current threshold set. Connect with an R
(ONLY IF VCC is supplied by 5V bus) to program OC threshold. When
VCC > 5V, R
HS Driver return path, current-reading and adaptive-dead-time monitor.
Connect to the LS drain to sense R
current. This pin is also used by the adaptive-dead-time control circuitry to
monitor when HS mosfet is OFF.
to the output regulated voltage. Additional
to GND may be used to regulate voltages higher than the
OS
OCSET
FB
need to be not-connected.
drop to measure the output
dsON
- CF // CP to FB to
F
resistor to VCC
OCSET
5/22
Electrical specifications L6727
2.2 Thermal data
Table 3. Thermal data
Symbol Parameter Value Unit
R
thJA
T
MAX
T
STG
T
J
1. Measured with the component mounted on a 2S2P board in free air (6.7cm x 6.7cm, 35µm (P) and 17.5µm
(S) copper thickness).
Thermal Resistance Junction to Ambient
Maximum Junction Temperature 150 °C
Storage Temperature Range -40 to 150 °C
Junction Temperature Range -20 to 150 °C
(1)
85 °C/W
3 Electrical specifications
3.1 Absolute maximum ratings
Table 4. Absolute maximum ratings
Symbol Parameter
(1)
Val ue Un it
V
V
BOOT
V
UGATE
CC
to GND -0.3 to 15 V
to PHASE
to GND
to PHASE
-0.3 to (V
to PHASE; t < 50ns
to GND
V
PHASE
V
LGATE
to GND -8 to 30 V
to GND
to GND; t < 50ns
COMP to GND -0.3 to 7 V
FB to GND -0.3 to 3.6 V
1. ESD immunity for FB pin is guaranteed up to ±1000V (Human Body Model).
BOOT
V
BOOT
-0.3 to V
15
45
- V
-1
+ 0.3
CC
-1
PHASE)
+ 0.3
V
+ 0.3
V
V
6/22
L6727 Electrical specifications
3.2 Electrical characteristics
Table 5. Electrical characteristics
(V
= 12V; TA = -20°C to +85°C, unless otherwise specified).
CC
Symbol Parameter Test conditions Min. Typ. Max. Unit
Recommended operating conditions
V
V
Device supply voltage
CC
Conversion input voltage
IN
Supply current and power-ON
I
CC
I
BOOT
VCC supply current UGATE and LGATE = OPEN 6 mA
BOOT supply current UGATE = OPEN; PHASE to GND 0.5 mA
VCC turn-ON VCC Rising 4.1 V
UVLO
Hysteresis 0.2 V
Oscillator
∆V
d
F
MAX
Main oscillator accuracy
SW
PWM ramp amplitude 1.5 V
OSC
Maximum duty cycle 80 %
Reference
Output voltage accuracy
Error amplifier
A
DC gain
0
(1)
GBWP Gain-bandwidth product
SR Slew-rate
(1)
See Figure 1
4.1 13.2 V
13.2 V
V
< 7.0V 19.0 V
CC
0°C to +70°C 270 300 330 kHz
250 300 350 kHz
V
= 0.8V, TA = 0°C to 70°C -1 - 1 %
OUT
= 0.8V -1.5 1.5 %
V
OUT
120 dB
(1)
15 MHz
8V/µs
I
FB
Input bias current Sourced from FB 100 nA
DIS Disable threshold COMP Falling 0.43 0.5 V
7/22
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