2.1A Synchronous Current Boost DC/DC Regulator

Preliminary Datasheet
LP6250
2.1A Synchronous Current Boost DC/DC Regulator
General Description
Features
The LP6250 is high efficiency Synchronous Boost
DC/DC Converter, fixed frequency, current-mode
step-up converter with output to input disconnect. A
PWM step-up DC/DC converters optimized to
provide a high efficiency solution to medium power
system. Its PWM circuitry with built-in
[email protected] power mosfet makes this converter
highly power efficiently. Selectable high switching
frequency allows faster loop response and easy
filtering with a low noise output. The non-inverting
input its error amplifier is connected to an internal
0.5V precision reference voltage. Soft-start time can
be programmed with an external capacitor, which
sets the input current ramp rate. Current mode
control and external compensation network make it
easy and flexible to stabilize the system. the devices
regulates the output voltage up to 5V from either a
2cell NiMH/NiCd or a single-cell Li-ion Battery
with a 500KHz fixed frequency switching. These
features minimize overall solution footprint by
allowing the use of tiny, low profile inductors and
ceramic capacitors.
‹
Up to 94% efficiency ‹
Shut-down current:<1uA ‹
Output voltage Up to 5V
‹ 500KHz fixed frequency switching
‹ High switch on current:[email protected]
Available in TDFN-10 Package ‹
Applications
—
—
—
Battery products
Host Products
Motor Power Devices
Typical Application Circuit
LP6250QVF
Vin
5V
9
6.8uH
C1
22uF
6
□ □
2
R3
100K
BATT
7
ON/OFF
1
R5
LBI
LBO
EN
FB
R5
5
GND
GND
4
R1
90K
10
Pin Configurations
Package Type
QV: TDFN-10
Marking Information
EN
1
10
GND
OUT
2
9
SW
FB
3
8
NC
LBO
4
7
LBI
GND
5
6
BATT
11
GND
Please see website.
LP6250 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
LBO
3
□
F: Pb-Free
C2
47uF
R4
Ordering Information
LP6250 -
OUT
SW
Page 1 of 8
R2
10K
C3
22pF
Preliminary Datasheet
LP6250
Functional Pin Description
PIN
PIN Name
Description
1
EN
2
3
Out
FB
4
5,10
6
7
8
9
LBO
GND
BATT
LBI
NC
SW
11
EPGND
Regulator On/off Control Input. A logic high input(VEN>1.4V) turns on
the regulator. A logic low input(VEN<0.4V) puts the LP6250 into low
current shutdown mode.
Voltage output pin.
Regulation Feedback Input. Connect to an external resistive voltage
divider from the output to FB to set the output voltage.
Open-drain Low Battery Detector output pin.
Power Ground.
Battery supply input pin.
Battery detector input pin.
No Connector.
Output switching node. SW is the drain of the internal N-Channel
MOSFET and RDS-ON is 250mΩ. Connect the inductor to SW to
Complete the step-up converter.
Exposed PAD. Must connect to Ground.
SW
Function Block Diagram
LP6250 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 2 of 8
Preliminary Datasheet
LP6250
Absolute Maximum Ratings
Supply Input Voltage---------------------------------------------------------------------------------------------------------------6V
Power Dissipation, PD @ TA = 25°C
TDFN-10--------------------------------------------------------------------------------------------------------600mW
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------------------260°C
Storage Temperature Range --------------------------------------------------------------------------------- −65°C to 150°C
Recommended Operating Conditions
Supply Input Voltage------------------------------------------------------------------------------------------------- 2.2V to 6V
SW Pin Voltage----------------------------------------------------------------------------------------------------------------- 7V
EN Input Voltage -------------------------------------------------------------------------------------------------------0V to 5.5V
Operation Junction Temperature Range ------------------------------------------------------------------−40°C to 125°C
Operation Ambient TemperatureRange----------------------------------------------------------------------−40°C to 85°C
Electrical Characteristics
Parameter
Conditions
LP6250
Supply Voltage
Min
2.2
Output Voltage Range
2.5
Supply Current(Shutdown)
Supply Current
Disable Supply Current
Feedback Voltage
Feedback Input Current
Switching Frequency
VEN=VOUT=0V,VSW=5V
VFB=1.3V
EN=GND
VFB=1.2V
FREQ
Maximum Duty Cycle
80
Low Battery Detector Input
EN Input Low Voltage
EN Input High Voltage
Mosfet On Resistance
Mosfet Voltage(VDS)
NMOS Current Limit
Soft-start Reset Switch Resistance
Soft-start Input Source Current
LP6250 –00 Version 1.0 Datasheet
Typ.
Units
Max
5
V
5
V
0.05
0.2
0.1
0.5
50
500
1
uA
mA
uA
V
nA
KHz
85
90
%
0.5
V
0.4
1.4
Ron(N-mos)
Ron(P-mos)
235
250
14
2.1
100
VSS=1.2V
Sep.-2010
4.0
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Page 3 of 8
V
V
mΩ
mΩ
V
A
Ω
uA
Preliminary Datasheet
LP6250
Typical Operating Characteristics (VDD=3.3V,Vout=5V)
LP6250 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 4 of 8
Preliminary Datasheet
LP6250 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
LP6250
Page 5 of 8
Preliminary Datasheet
LP6250
Operation Information
Output Voltage
The error amplifier compares a sample of the dc-dc
converter output voltage with the 0.5V (VREF)
reference and generates an error signal for the PWM
comparator. Output voltage of dc-dc converter is
setting with the resistor divider by the following
equation:
Vout=(R1/R2+1) X 0.5V
Oscillator
The switching frequency of LP6250 up to operate at
either 500KHz.
Soft Start
The soft start is functional after power on. The
interval of soft start time is determined by a
capacitor connected to SS pin. When EN pin is
taken high, the soft start capacitor (CSS) is charged
by a constant current of 4μA (typ.). During this
interval, the SS voltage directly controls the peak
inductor current. The maximum load current is
available after the soft-start interval is completed.
Once the EN pin is taken low, the soft-start
capacitor is discharged to ground to prepare for next
start-up.
The load must wait for the soft-start interval to
finish before drawing a significant amount of load
current. The duration after which the load can begin
to draw maximum load current is:
EN
The LP6250 can be turn off to reduce the supply
current to 0.1μA when EN is low. In this mode, the
internal reference, error amplifier, comparators, and
biasing circuitry turn off while the N-channel
MOSFET is turned off. The boost converter’s
output is connected to VCC by the external inductor
and catch diode.
Output Current Capability
The output current capability of the LP6250 is a
function of current limit, input voltage, operation
frequency, and inductor value. Because of the slope
compensation used to stabilize the feedback loop,
the duty cycle affects the current limit. The output
LP6250 –00 Version 1.0 Datasheet
Sep.-2010
current capability is governed by the following
equation:
Current Limitation
The internal power-MOS switch current is
monitored cycle-by-cycle and is limited to the value
not exceed 2.1A (Typ.). When the switch current
reaches the limited value, the internal power-MOS
is turned off immediately until the next cycle.
Low Battery Detector
The LP6250 provides an on-chip comparator with
35mV internal hysteresis for low battery detection.If
the LBI pin voltage falls below the internal
reference voltage(0.5V),the LBO pin(an open-drain
output) sinks current to GND.The LBI pin should be
connected to BAT pin if the low battery comparator
is not used.
Layout considerations
Typical for all switching power supplies, the
layout is an important step in the design;
especially at high peak-currents and
switching frequencies. If the layout is not
carefully done, the regulator might show
noise problem sand duty cycle fitter. The
input capacitor should be placed as close as
possible to the input pin for good input
voltage viltering. The inductor and diode
should be placed as close as possible to the
switch pin to minimize the noise coupling in
to other circuits. Since the feedback pin and
network is a high impedance circuit the
feedback network should be routed away
from the inductor. The feedback pin and
feedback network should be shielded with a
ground plane or trace to minimize noise
coupling into this circuit.
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Page 6 of 8
Preliminary Datasheet
LP6250
Application Circuit Information
LP6250QVF
Vin
5V
9
6.8uH
C1
47uF
6
SW
OUT
2
R3
100K
BATT
C2
47uF
R4
7
ON/OFF
1
R5
LBI
LBO
EN
FB
R5
5
GND
GND
4
LBO
R1
90K
C3
22pF
3
10
R2
10K
Figure1. LP6250 application circuit of used Low Battery Circuit
LP6250QVF
Vin
5V
9
6.8uH
C1
47uF
6
SW
OUT
2
R3
100K
BATT
C2
47uF
R4
7
ON/OFF
1
LBI
LBO
EN
FB
R5
5
GND
GND
4
LBO
R1
90K
C3
22pF
3
10
R2
10K
Figure2. LP6250 application of not used Low Battery Circuit
Layout Circuit Information
LP6250 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 7 of 8
Preliminary Datasheet
LP6250
Packaging Information
LP6250 –00 Version 1.0 Datasheet
Sep.-2010
www.lowpowersemi.com
Page 8 of 8