|
|
PDF LTC3407 Data sheet ( Hoja de datos )
| Número de pieza | LTC3407 | |
| Descripción | Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LTC3407 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
FEATURES
n High Efficiency: Up to 96%
n Very Low Quiescent Current: Only 40μA
n 1.5MHz Constant Frequency Operation
n High Switch Current: 1A on Each Channel
n No Schottky Diodes Required
n Low RDS(ON) Internal Switches: 0.35Ω
n Current Mode Operation for Excellent Line
and Load Transient Response
n Short-Circuit Protected
n Low Dropout Operation: 100% Duty Cycle
n Ultralow Shutdown Current: IQ < 1μA
n Output Voltages from 5V down to 0.6V
n Power-On Reset Output
n Externally Synchronizable Oscillator
n Small Thermally Enhanced MSOP and 3mm × 3mm
DFN Packages
APPLICATIONS
n PDAs/Palmtop PCs
n Digital Cameras
n Cellular Phones
n Portable Media Players
n PC Cards
n Wireless and DSL Modems
LTC3407
Dual Synchronous, 600mA,
1.5MHz Step-Down
DC/DC Regulator
DESCRIPTION
The LTC®3407 is a dual, constant frequency, synchronous
step down DC/DC converter. Intended for low power ap-
plications, it operates from 2.5V to 5.5V input voltage
range and has a constant 1.5MHz switching frequency,
allowing the use of tiny, low cost capacitors and inductors
2mm or less in height. Each output voltage is adjustable
from 0.6V to 5V. Internal synchronous 0.35Ω, 1A power
switches provide high efficiency without the need for
external Schottky diodes.
A user selectable mode input is provided to allow the user
to trade-off ripple noise for low power efficiency. Burst
Mode® operation provides high efficiency at light loads,
while pulse-skipping mode provides low ripple noise at
light loads.
To further maximize battery life, the P-channel MOSFETs
are turned on continuously in dropout (100% duty cycle),
and both channels draw a total quiescent current of only
40μA. In shutdown, the device draws <1μA.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
VIN = 2.5V
TO 5.5V
C1
10μF
VOUT2 = 2.5V
AT 600mA
L2
2.2μH
C5, 22pF
RUN2 VIN RUN1
MODE/SYNC
POR
LTC3407
SW2 SW1
R5
100k
RESET
L1
2.2μH
C4, 22pF
C3
10μF
R4
887k R3
280k
VFB2
GND
VFB1
R2
R1 887k
442k
VOUT1 = 1.8V
AT 600mA
C2
10μF
C1, C2, C3: TAIYO YUDEN JMK316BJ106ML
L1, L2: MURATA LQH32CN2R2M33
Figure 1. 2.5V/1.8V at 600mA Step-Down Regulators
3407 TA01
LTC3407 Efficiency Curve
100
95 2.5V
90 1.8V
85
80
75
70
65
VIN = 3.3V
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
60
1
10 100
LOAD CURRENT (mA)
1000
3407 TA02
3407fa
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC3407
Efficiency vs Load Current
100
95
3.3V 2.7V
90
85 4.2V
80
75
70
65
60
1
VOUT = 1.2V Burst Mode OPERATION
CIRCUIT OF FIGURE 1
10 100
LOAD CURRENT (mA)
1000
3407 G13
Efficiency vs Load Current
100
95
3.3V 2.7V
90
85 4.2V
80
75
70
65
60
1
VOUT = 1.5V Burst Mode OPERATION
CIRCUIT OF FIGURE 1
10 100
LOAD CURRENT (mA)
1000
3407 G14
Line Regulation
0.5
0.4
VOUT = 1.8V
IOUT = 200mA
0.3 TA = 25°C
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
2
34
VIN (V)
56
3407 G15
PIN FUNCTIONS
VFB1 (Pin 1): Output Feedback. Receives the feedback volt-
age from the external resistive divider across the output.
Nominal voltage for this pin is 0.6V.
RUN1 (Pin 2): Regulator 1 Enable. Forcing this pin to VIN
enables regulator 1, while forcing it to GND causes regulator
1 to shut down. This pin must be driven; do not float.
VIN (Pin 3): Main Power Supply. Must be closely decoupled
to GND.
SW1 (Pin 4): Regulator 1 Switch Node Connection to the
Inductor. This pin swings from VIN to GND.
GND (Pin 5): Ground. This pin is not connected internally.
Connect to PCB ground for shielding.
MODE/SYNC (Pin 6): Combination Mode Selection and
Oscillator Synchronization. This pin controls the opera-
tion of the device. When tied to VIN or GND, Burst Mode
operation or pulse-skipping mode is selected, respectively.
Do not float this pin. The oscillation frequency can be
synchronized to an external oscillator applied to this pin
and pulse-skipping mode is automatically selected.
SW2 (Pin 7): Regulator 2 Switch Node Connection to the
Inductor. This pin swings from VIN to GND.
POR (Pin 8): Power-On Reset . This common-drain logic
output is pulled to GND when the output voltage is not
within ±8.5% of regulation and goes high after 175ms
when both channels are within regulation.
RUN2 (Pin 9): Regulator 2 Enable. Forcing this pin to VIN
enables regulator 2, while forcing it to GND causes regulator
2 to shut down. This pin must be driven; do not float.
VFB2 (Pin 10): Output Feedback. Receives the feedback
voltage from the external resistive divider across the output.
Nominal voltage for this pin is 0.6V.
Exposed Pad (GND) (Pin 11): Power Ground. Connect to
the (–) terminal of COUT, and (–) terminal of CIN. Must be
soldered to electrical ground on PCB.
3407fa
5
5 Page 
LTC3407
APPLICATIONS INFORMATION
produce the most improvement. Percent efficiency can
be expressed as:
%Efficiency = 100% - (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, 4 main sources usually account for most of the
losses in LTC3407 circuits: 1)VIN quiescent current, 2)
switching losses, 3) I2R losses, 4) other losses.
1) The VIN current is the DC supply current given in the
Electrical Characteristics which excludes MOSFET driver
and control currents. VIN current results in a small (<0.1%)
loss that increases with VIN, even at no load.
2) The switching current is the sum of the MOSFET driver
and control currents. The MOSFET driver current results
from switching the gate capacitance of the power MOSFETs.
Each time a MOSFET gate is switched from low to high
to low again, a packet of charge dQ moves from VIN to
ground. The resulting dQ/dt is a current out of VIN that is
typically much larger than the DC bias current. In continu-
ous mode, IGATECHG = fO(QT + QB), where QT and QB are
the gate charges of the internal top and bottom MOSFET
switches. The gate charge losses are proportional to VIN
and thus their effects will be more pronounced at higher
supply voltages.
3) I2R losses are calculated from the DC resistances of the
internal switches, RSW, and external inductor, RL. In con-
tinuous mode, the average output current flowing through
inductor L, but is “chopped” between the internal top and
bottom switches. Thus, the series resistance looking into
the SW pin is a function of both top and bottom MOSFET
RDS(ON) and the duty cycle (DC) as follows:
RSW = (RDS(ON)TOP)(DC) + (RDS(ON)BOT)(1 – DC)
The RDS(ON) for both the top and bottom MOSFETs can
be obtained from the Typical Performance Characteristics
curves. Thus, to obtain I2R losses:
I2R losses = (IOUT)2 (RSW + RL)
4) Other ‘hidden’ losses such as copper trace and internal
battery resistances can account for additional efficiency
degradations in portable systems. It is very important
to include these “system” level losses in the design of a
system. The internal battery and fuse resistance losses
can be minimized by making sure that CIN has adequate
charge storage and very low ESR at the switching frequency.
Other losses including diode conduction losses during
dead-time and inductor core losses generally account for
less than 2% total additional loss.
Thermal Considerations
In a majority of applications, the LTC3407 does not dis-
sipate much heat due to its high efficiency. However, in
applications where the LTC3407 is running at high ambient
temperature with low supply voltage and high duty cycles,
such as in dropout, the heat dissipated may exceed the
maximum junction temperature of the part. If the junction
temperature reaches approximately 150°C, both power
switches will be turned off and the SW node will become
high impedance.
To prevent the LTC3407 from exceeding the maximum
junction temperature, the user will need to do some thermal
analysis. The goal of the thermal analysis is to determine
whether the power dissipated exceeds the maximum
junction temperature of the part. The temperature rise is
given by:
TRISE = PD • θJA
where PD is the power dissipated by the regulator and θJA
is the thermal resistance from the junction of the die to
the ambient temperature.
The junction temperature, TJ, is given by:
TJ = TRISE + TAMBIENT
As an example, consider the case when the LTC3407 is
in dropout on both channels at an input voltage of 2.7V
with a load current of 600mA and an ambient temperature
of 70°C. From the Typical Performance Characteristics
graph of Switch Resistance, the RDS(ON) resistance of
the main switch is 0.425Ω. Therefore, power dissipated
by each channel is:
PD = IOUT2 • RDS(ON) = 153mW
The MS package junction-to-ambient thermal resistance,
θJA, is 45°C/W. Therefore, the junction temperature of
3407fa
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC3407.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LTC3400 | 600mA/ 1.2MHz Micropower Synchronous Boost Converter in ThinSOT | Linear Technology |
| LTC3400-1 | 1.2MHz Micropower Synchronous Boost Converter |  Linear |
| LTC3400B | 600mA/ 1.2MHz Micropower Synchronous Boost Converter in ThinSOT | Linear Technology |
| LTC3400BES6 | 600mA/ 1.2MHz Micropower Synchronous Boost Converter in ThinSOT | Linear Technology |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |