EUTECH EUP6514

EUP6514
5V/12V Synchronous Buck
PWM Controller
DESCRIPTION
FEATURES
The EUP6514 is a high efficiency, fixed 300kHz
frequency, voltage mode, synchronous PWM controller.
The device drives two low cost N-channel MOSFETs
and is designed to work with 5V to 12V supply voltage,
providing excellent regulation for load transients.
The EUP6514 includes soft-start, frequency
compensation networks nd integrates all of the controls,
output adjustments, monitoring and protection
functions into a single package.
A power-on-reset (POR) circuit monitors the power
supply to prevent wrong logic controls. The built-in
soft-start with fixed soft-start internal prevents the
output voltage from overshoot as well as limiting the
input current. Adjustable over-current protection
monitors the voltage drop across the RDS(ON) of the
lower MOSFET, with no current sense resistor
required. The EUP6514 is available in 8-pins SOP
package.
Pulling and holding the voltage on OPS pin below
0.1V with an open drain device shuts down the
controller.
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APPLICATIONS
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Typical Application Circuit
Figure 1.
DS6514
Ver 1.1
Aug. 2008
Operating with 5~12V Supply Voltage
300 kHz Fixed Frequency Oscillator
Built-In Feedback Compensation
-Voltage-mode PWM Control with 0 to 100%
Duty Ratio
Fast Transient Response
-High-Speed GM Amplifier
Drives All Low Cost N-Channel MOSFETs
-Adaptive Shoot-Through Protection
Adjustable Over-Current Protection
-Using RDS(ON) of the Low-side MOSFET
Built-In Soft-Start
Shutdown Control using an External
Available in SOP-8
RoHS Compliant and 100% Lead (Pb)-Free
1
Motherboard
Graphics Card
High Current, up to 20A, DC-DC Converter
Telecomm Equipments
IA Equipments
EUP6514
Pin Configurations
Package Type
Pin
Configurations
SOP-8
Pin Description
PIN
PIN
1
BOOT
2
UGATE
3
GND
4
LGATE
5
VCC
6
FB
7
OPS
8
DS6514
PHASE
Ver 1.1
Aug. 2008
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.
Upper gate driver output. Connect to the gate of high-side power N-Channel
MOSEFT. This pin is monitored by the adaptive shoot-through protection circuitry to
determine when the upper MOSFET has turned off.
Both signal and power ground for the IC. All voltage levels are measured with
respect to this pin. Ties the pin directly to the low-side MOSFET source and ground
plane with the lowest impedance.
Lower gate drive output. Connect to the gate of low-side power N-Channel
MOSFET. This pin is monitored by the adaptive shoot-through protection circuitry to
determine when the lower MOSFET has turned off.
Connect this pin to a well-decoupled 5V or 12V bias supply. It is also the positive
supply for the lower gate driver, LGATE.
Switcher feedback voltage. This pin is the inverting input of the error amplifier. FB
senses the switcher output through an external resistor divider network.
This pin provides multi-function of the over-current setting, UGATE turn-on POR
sensing, and shut-down features. Connecting a resistor (ROCSET) between OPS and
PHASE pins sets the over-current trip point.
Pulling the pin to ground resets the device and all external MOSFETs are turned off
allowing the output voltage power rails to float.
This pin is also used to detect VIN in power on stage and issues an internal POR
signal.
Connect this pin to the source of the upper MOSEFT and the drain of the lower
MOSFET.
2
EUP6514
Block Diagram
Figure 2.
DS6514
Ver 1.1
Aug. 2008
3
EUP6514
Ordering Information
Order Number
Package Type
EUP6514DIR1
SOP-8
EUP6514
Marking
xxxxx
P6514
□ □ □ □
Lead Free Code
1: Lead Free 0: Lead
Packing
R: Tape& Reel
Operating temperature range
I: Industry Standard
Package Type
D: SOP
DS6514
Ver 1.1
Aug. 2008
4
Operating Temperature Range
-40 °C to 85°C
EUP6514
Absolute Maximum Ratings
„
„
„
„
„
„
„
„
„
„
„
„
„
Supply Voltage (VCC)
-------------------------------------------------------------------------- 16V
BOOT, VBOOT-VPHASE --------------------------------------------------------------------------- 16V
PHASE to GND
DC ----------------------------------------------------------------------------------------- -1V to 15V
BOOT to PHASE -------------------------------------------------------------------------------- 15V
BOOT to GND
DC -------------------------------------------------------------------------------- -0.3V to VCC+15V
UGATE ------------------------------------------------------------- VPHASE -0.3V to VBOOT +0.3V
LGATE ---------------------------------------------------------------- GND -0.3V to VVCC +0.3V
Input, Output or I/O Voltage --------------------------------------------------- GND -0.3V to 7V
Package Thermal Resistance
SOP-8, θJA --------------------------------------------------------------------------------- 67.9°C /W
Junction Temperature ------------------------------------------------------------------------ 150°C
Storage Temperature (Solding, 10sec.) ----------------------------------------------------- 260°C
ESD Susceptibility
HBM (Human Body Mode) -------------------------------------------------------------------- 2kV
Recommended Operating Conditions
„
„
„
Supply Voltage, VCC ---------------------------------------------------------- 5V±5%, 12V±10%
Ambient Temperature Range ------------------------------------------------------ -40°C to 85°C
Junction Temperature Range ---------------------------------------------------- -40°C to 125°C
Electrical Characteristics
Symbol
Parameter
VCC Supply Current
ICC
Norminal Supply Current
ICCS
Shutdown Supply Current
Power-on Reset
VCCRTH
POR Threshold
VCCHYS
Hysteresis
Switcher Reference
VREF
Reference Voltage
Oscillator
fOSC
Free Running Trequency
Ramp
∆VOSC
Amplitude
Error Amplifier
DC Gain
FP1
First Pole Frequency
FZ
Zero Frequency
FP2
Second Pole Frequency
FB Input Current
PWM Controller Gate Drivers
RUGATE_H
UGATE source Rdson
RUGATE_L
UGATE sink Rdson
RLGATE_H
LGATE source Rdson
RLGATE_L
LGATE sink Rdson
TDT
Dead Time
Protection
UVP
Under Voltage Level
IOC
OC Current Source
Over-current Reference
Voltage
TSS
Soft-Start Interval
VOPS_SHUT
OPS Shutdown Threshold
DS6514
Ver 1.1
Aug. 2008
Conditions
Min.
UGATE and LGATE open
EUP6514
Typ.
Max.
Unit
2
1.2
5
2.5
mA
mA
4.2
400
4.5
200
V
mV
VCC=12V
0.784
0.8
0.816
V
VCC=12V
250
300
360
kHz
VCC Rising
VCC=12V
1.5
VP-P
80
1
1
400
dB
Hz
kHz
kHz
µA
0.1
VCC=12V, IUGATE=10mA
VUGATE=1V, IUGATE=10mA
VCC=12V, ILGATE=10mA
VLGATE=1V, IUGATE=10mA
FB Falling
VPHASE=0
Falling VOPS
5
68
35
0.08
5
3
5
3
50
8
6
8
6
Ω
Ω
Ω
Ω
ns
73
40
78
45
%
µA
0.4
V
4
0.1
mS
V
0.13
EUP6514
Typical Operating Characteristics
DS6514
Ver 1.1
Aug. 2008
6
EUP6514
Typical Operating Characteristics (continued)
DS6514
Ver 1.1
Aug. 2008
7
EUP6514
Typical Operating Characteristics (continued)
DS6514
Ver 1.1
Aug. 2008
8
EUP6514
According to Figure 1 the ripple current of inductor
can be calculated as follows :
Application Information
Inductor Selection
VIN − VOUT = L
The selection of output inductor is based on the
considerations of efficiency, output power and
operating frequency. Low inductance value has smaller
size, but results in low efficiency, large ripple current
and high output ripple voltage. Generally, an inductor
that limits the ripple current (∆IL) between 20% and
50% of output current is appropriate. Figure 3 shows
the typical topology of synchronous step-down
converter and its related waveforms.
D
V
∆IL
; ∆t = ; D = OUT
∆t
fs
VIN
L = (VIN − VOUT ) ×
VOUT
VIN × fs × ∆IL
Where:
VIN = Maximum input voltage
VOUT = Output Voltage
∆t = S1 turn in time
∆IL = Inductor current ripple
fs = Switching frequency
D = Duty Cycle
rC = Equivalent series resistor of output capacitor
Output Capacitor
The selection of output capacitor depends on the output
ripple voltage requirement. Practically, the output
ripple voltage is a function of both capacitance value
and the equivalent series resistance (ESR) rC. Figure 4
shows the related waveforms of output capacitor.
Figure 3.The waveforms of synchronous
step-down converter
DS6514
Ver 1.1
Aug. 2008
Figure 4.The related waveforms of output
capacitor
9
EUP6514
Below Figures say those effects. And test conditions
are Rocset=15kΩ (over-current trip point=20.6A),
Low-side MOSFET is IR3707.
The AC impedance of output capacitor at operating
flows mainly through output capacitor. The output
ripple voltage is described as:
2. VIN_POR
∆ V OUT = ∆V OR + ∆ V OC + V OC
(2)
1
= ∆IL × rc +
CO
(3)
∆ V OUT
∫
t2
t1
∆ V OUT = ∆IL × ∆IL × rc +
ic dt
1 V OUT
(1 − D )TS2
8 C OL
UGATE will continuously generate a 10kHz clock
with 1% duty cycle before VIN is recognized ready by
detecting VOPS crossing 1.5V four times (rising &
falling). ROCSET must be kept lower than 37.5kΩ for
large ROCSET will keep VOPS always higher than 1.5V.
Figure 6 shows the detail actions of OCP and POR. It
is highly recommend-ed that ROCSET be lower than
30kΩ.
(4)
Where △VOR is by ESR and ΔVOC by capacitance.
For electrolytic capacitor application, typically 90 to
95% of the output voltage ripple is contributed by the
ESR of output capacitor. So Equation (4) could be
simplified as :
∆ V OUT = ∆IL × rc
(5)
Users could connect capacitors in parallel to get
calculated ESR.
Output Capacitor
The selection of input capacitor is mainly based on its
maximum ripple current capability. The buck converter
draws pulsewise current from the input capacitor
during the on time of S1 as shown in Figure 3. The
RMS value of ripple current flowing through the input
capacitor is described as:
Irms = IOUT D (1 − D ) (A )
(6)
Figure 5. UV_FB trigger VIN power sensing
The input capacitor must be cable of handling this
ripple current. Sometime, for higher efficiency the low
ESR capacitor is necessarily.
3. Shutdown
OPS (Over Current Setting, VIN_POR and
Shutdown)
Pulling low the OPS pin by a small single transistor
can shutdown the EUP6514 PWM controller as
shown in typical application circuit.
1.OCP
Soft Start
Sense the low-side MOSFET’s RDS(ON) to set
over-current trip point.
A built-in soft-start is used to prevent surge current
from power supply input during power on. The
soft-start voltage is controlled by an internal digital
counter. It clamps the ramping of reference voltage at
the input of error amplifier and the pulse-width of the
output driver slowly. The typical soft-start duration is
3ms.
Connecting a resistor (ROCSET) from this pin to the
source of the upper MOSFET and the drain of the
lower MOSFET sets the over-current trip point. ROCSET,
an internal 40µA current source, and the lower
MOSFET on resistance, RDS(ON), set the converter
over-current trip point (IOCSET) according to the
following equation :
IOCSET =
40 µA × R OCSET − 0.4 V
R DS ( ON ) of the lower MOSFET
OPS pin function is similar to RC charging or
charging or discharging circuit, so the over-current
trip point is very sensitive to parasitic capacitance (ex.
Shut-down MOSFET) and the duty ratio.
DS6514
Ver 1.1
Aug. 2008
10
EUP6514
output inductor and output capacitors between the
MOSEFTs and the load. Also locate the PWM
controller near by MOSFETs.
Under Voltage Protection
The voltage at FB pin is monitored and protected
against UV (under voltage). The UV threshold is the
FB or FBL under 80%. UV detection has 15µs
triggered delay. A hiccup restart sequence will be
operating until UV state is exited.
A multi-layer printed circuit board is recommended.
Figure 6.
PWM Layout Considerations
MOSFETs switch very fast and efficiently. The speed
with which the current transitions form one device to
another causes voltage spikes across the
interconnecting impedances and parasitic circuit
elements. The voltage spikes can degrade efficiency
and radiate noise, that results in over-voltage stress on
devices. Careful component placement layout and
printed circuit design can minimize the voltage spikes
induced in the converter. Consider, as an example, the
turn-off, the upper MOSFET was carrying the full
load current. During turn-off, current stops flowing in
the upper MOSFET and is picked up by the low side
MOSFET or schottky diode. Any inductance in the
switched current path generates a large voltage spike
during the switching interval. Careful component
selections, layout of the critical components, and use
shorter and wider PCB traces help in minimizing the
magnitude of voltage spikes.
There are two sets of critical components in a DC-DC
converter using the EUP6514. The switching power
components are most critical because they switch
large amounts of energy, and as such, they tend to
generate equally large amounts of noise. The critical
small signal components are those connected to
sensitive nodes or those supplying critical bypass
current.
The power components and the PWM controller
should be placed firstly. Place the input capacitors,
especially the high-frequency ceramic decoupling
capacitors, close to the power switches. Place the
DS6514
Ver 1.1
Aug. 2008
11
EUP6514
Packaging Information
SOP-8
SYMBOL
S
A
A1
D
E
E1
L
b
e
DS6514
Ver 1.1
Aug. 2008
MILLIMETERS
MIN.
MAX.
1.35
1.75
0.10
0.25
4.90
5.80
6.20
3.90
0.40
1.27
0.31
0.51
1.27
12
INCHES
MIN.
0.053
0.004
0.193
0.228
0.153
0.016
0.012
0.050
MAX.
0.069
0.010
0.244
0.050
0.020