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PDF UP6109 Data sheet ( Hoja de datos )
| Número de pieza | UP6109 | |
| Descripción | 5V/12V Synchronous-Rectified Buck Controller | |
| Fabricantes | uPI Semiconductor | |
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uP6109
5V/12V Synchronous-Rectified
Buck Controller with Enable Input
General Description
Features
The uP6109 is a compact synchronous-rectified buck
controller specifically designed to operate from 5V or 12
supply voltage and to deliver high quality output voltage as
low as 0.8V. This (P)SOP-8 device operates at fixed 300
kHz frequency and provides an optimal level of integration
to reduce size and cost of the power supply.
This controller integrates internal MOSFET drivers that
support 12V+12V bootstrapped voltage for high efficiency
power conversion. The bootstrap diode is built-in to simplify
the circuit design and minimize external part count.
Other features include internal softstart, undervoltage
protection, overcurrent protection and shutdown function.
With aforementioned functions, this part provides
customers a compact, high efficiency, well-protected and
cost-effective solutions. This part is available in (P)SOP-8
packages.
Ordering Information
Order Number Package Type
Remark
uP6109ASA8
SOP-8
uP6109ASU8 PSOP-8
Note: uPI products are compatible with the current IPC/
JEDEC J-STD-020 and RoHS requirements. They are 100%
matte tin (Sn) plating and suitable for use in SnPb or Pb-
free soldering processes.
Operate from 5V or 12V Supply Voltage
3.3V to 12V V Input Range
IN
0.8 VREF with 1.5% Accuracy
Output Range from VREF to 80% of VIN
Simple Single-Loop Control Design
Voltage-Mode PWM Control
Fast Transient Response
High-Bandwidth Error Amplifier
0% to 80% Duty Cycle
Lossless, Programmable Overcurrent Protection
Uses Lower MOSFET RDS(ON)
300 kHz Fixed Frequency Oscillator
Internal Soft Start
Integrated Bootstrap Diode
Applications
Power Supplies for Microprocessors or
Subsystem Power Supplies
Cable Modems, Set Top Boxes, and xDSL
Modems
Industrial Power Supplies; General Purpose
Supplies
5V or 12V Input DC-DC Regulators
Low Voltage Distributed Power Supplies
Pin Configuration & Typical Application Circuit
VIN
BOOT
UGATE
GND
LGATE
BOOT
UGATE
GND
LGATE
18
27
36
45
SOP-8
18
27
GND
36
45
PSOP-8
PHASE
EN
FB
VCC
Disable
Enable
EN
7
PHASE
EN
FB
VCC
FB
6
Option
VCC
5
BOOT
1
UGATE
2
PHASE
8
LGATE
4
3
GND
VOUT
uPI Semiconductor Corp., http://www.upi-semi.com
Rev. F00, File Name: uP6109-DS-F0000
1
Free Datasheet http://www.Datasheet4U.com
1 page  
uP6109
Functional Description
OCP level can be calculated according the on-resistance
of the lower MOSFET used.
VIN
5V/Div
VOUT
0 .5 V /D iv
IOCP
=
− VOCP
RDS(ON)
(A)
LGATE
5 V /D iv
IX
2.5/Div
2ms/Div
Figure 2. Softstart Behavior.
Power Input Detection
The uP6109 detects PHASE voltage for the present of power
input when the UGATE turns on the first time. If the PHASE
voltage does not exceed 3.0V when the UGATE turns on,
the uP6109 asserts that power input in not ready and stops
the softstart cycle. However, the internal SS continues
ramping up to 4VDD. Another softstart is initiated after SS
ramps up to 4VDD. The hiccup period is about 12ms. Figure
3 shows the start up interval where VIN does not present
initially.
VIN
5V/Div
Connecting a resistance from LGATE to GND selects the
appropriate VOCP as shown in Table 1. Also shown in Table
1 is OCP level if a lower MOSFET with 10mΩ RDS(ON) is
used.
Table 1. OCP Level Selection
ROCP (Ω)
VOCP (mV)
IOCP (A)
open
-375
37.5
42k
-300
30
26k
-225
22.5
10k
-150
15
When programming the OCP level, take into consideration
the conditions that affect R of the lower MOSFET,
DS(ON)
including operation junction temperature, gate driving voltage
and distribution. Consider the RDS(ON) at maximum operation
temperature and lowest gate driving voltage.
Another factor should taken into consideration is the ripple
of the inductor current. The current near the valley of the
ripple current is used for OCP, resulting the averaged OCP
level a little higher than the calculated value.
Undervoltage Protection (UVP)
The FB voltage is monitored for undervoltage protection.
The UVP threshold level is typical 0.6V for both stand-
alone and tracking mode. The uP6109 shuts down upon
the detection of UVP and can be reset only by POR or
toggling EN pin.
VOUT
5V/Div
LGATE
5V/Div
1ms/Div
Figure 3. Softstart where VIN does not Present Initially.
Overcurrent Protection (OCP)
The uP6109 detects voltage drop across the lower MOSFET
(VPHASE) for overcurrent protection when it is turn on. If VPHASE
is lower than the user-programmable voltage VOCP, the
uP6109 asserts OCP and shuts down the converter. The
uPI Semiconductor Corp., http://www.upi-semi.com
Rev. F00, File Name: uP6109-DS-F0000
5
Free Datasheet http://www.Datasheet4U.com
5 Page 
uP6109
Application Information
Power MOSFET Selection
External component selection is primarily determined by
the maximum load current and begins with the selection of
power MOSFET switches. The uP6109 requires two
external N-channel power MOSFETs for upper (controlled)
and lower (synchronous) switches. Important parameters
for the power MOSFETs are the breakdown voltage V(BR)DSS,
on-resistance RDS(ON), reverse transfer capacitance CRSS,
maximum current I , gate supply requirements, and
DS(MAX)
thermal management requirements.
The gate drive voltage is powered by VCC pin that receives
4.5V~13.2V supply voltage. When operating with a 12V
power supply for VCC (or down to a minimum supply
voltage of 8V), a wide variety of NMOSFETs can be used.
Logic-level threshold MOSFET should be used if the input
voltage is expected to drop below 8V. Since the lower
MOSFET is used as the current sensing element, particular
attention must be paid to its on-resistance. Look for RDS(ON)
ratings at lowest gate driving voltage.
Both MOSFETs have I2R losses and the top MOSFET
includes an additional term for switching losses, which are
largest at high input voltages. The bottom MOSFET losses
are greatest when the bottom duty cycle is near 100%,
during a short-circuit or at high input voltage. These
equations assume linear voltage current transitions and do
not adequately model power loss due the reverse-recovery
of the lower MOSFET’s body diode. Ensure that both
MOSFETs are within their maximum junction temperature
at high ambient temperature by calculating the temperature
rise according to package thermal-resistance
specifications. A separate heatsink may be necessary
depending upon MOSFET power, package type, ambient
temperature and air flow.
The gate-charge losses are dissipated by the uP6109 and
don’t heat the MOSFETs. However, large gate charge
increases the switching interval, TSW that increases the
MOSFET switching losses. The gate-charge losses are
calculated as:
Special cautions should be exercised on the lower switch
exhibiting very low threshold voltage VGS(TH). The shoot-
through protection present aboard the uP6109 may be
circumvented by these MOSFETs if they have large
parasitic impedances and/or capacitances that would inhibit
the gate of the MOSFET from being discharged below its
threshold level before the complementary MOSFET is
turned on. Also avoid MOSFETs with excessive switching
times; the circuitry is expecting transitions to occur in under
50 nsec or so.
In high-current applications, the MOSFET power
dissipation, package selection and heatsink are the
dominant design factors. The power dissipation includes
two loss components; conduction loss and switching loss.
The conduction losses are the largest component of power
dissipation for both the upper and the lower MOSFETs.
These losses are distributed between the two MOSFETs
according to duty cycle. Since the uP6109 is operating in
continuous conduction mode, the duty cycles for the
MOSFETs is:
DUP
=
VOUT
VIN
;
DLO
=
VIN
− VOUT
VIN
The resulting power dissipation in the MOSFETs at
maximum output current are:
PUP = IO2 UT × RDS(ON) × DUP + 0.5 × IOUT × VIN × TSW × fOSC
PLO = IO2 UT × RDS(ON) × DLO
where TSW is the combined switch ON and OFF time.
PG = VCC × (VCC × (CISS _ UP + CISS _ LO ) + VIN × CRSS ) × fOSC
where CISS_UP is the input capacitance of the upper
MOSFET, CISS_LO is the input capacitance of the lower
MOSFET, and CRSS_UP is the reverse transfer capacitance
of the upper MOSFET. Make sure that the gate-charge loss
will not cause over temperature at uP6109, especially with
large gate capacitance and high supply voltage.
Output Inductor Selection
Output inductor selection usually is based the
considerations of inductance, rated current, size
requirement, and DC resistance (DC)
Given the desired input and output voltages, the inductor
value and operating frequency determine the ripple current:
ΔIL
=
1
fOSC × LOUT
× VOUT
× (1−
VOUT
VIN
)
Lower ripple current reduces core losses in the inductor,
ESR losses in the output capacitors and output voltage
ripple. Highest efficiency operation is obtained at low
frequency with small ripple current. However, achieving this
requires a large inductor. There is a tradeoff between
component size, efficiency and operating frequency. A
reasonable starting point is to choose a ripple current that
is about 40% of IOUT(MAX).
There is another tradeoff between output ripple current/
voltage and response time to a transient load. Increasing
the value of inductance reduces the output ripple current
and voltage. However, the large inductance values reduce
the converter’s response time to a load transient.
uPI Semiconductor Corp., http://www.upi-semi.com
Rev. F00, File Name: uP6109-DS-F0000
11
Free Datasheet http://www.Datasheet4U.com
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet UP6109.PDF ] | |
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