|
|
PDF LTC1436AIGN-PLL Data sheet ( Hoja de datos )
| Número de pieza | LTC1436AIGN-PLL | |
| Descripción | High Efficiency Low Noise Synchronous Step-Down Switching Regulators | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LTC1436AIGN-PLL (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
|
No Preview Available !
LTC1436A
LTC1436A-PLL/LTC1437A
High Efficiency Low Noise
Synchronous Step-Down
Switching Regulators
FEATURES
s Maintains Constant Frequency at Low Output Currents
s Dual N-Channel MOSFET Synchronous Drive
s Programmable Fixed Frequency (PLL Lockable)
s Wide VIN Range: 3.5V to 36V Operation
s Low Minimum On-Time (≤300ns) for High
Frequency, Low Duty Cycle Applications
s Very Low Dropout Operation: 99% Duty Cycle
s Low Dropout, 0.5A Linear Regulator for CPU I/O
or Low Noise Audio Supplies
s Built-In Power-On Reset Timer
s Programmable Soft Start
s Low-Battery Detector
s Remote Output Voltage Sense
s Foldback Current Limiting (Optional)
s Pin Selectable Output Voltage
s Logic Controlled Micropower Shutdown: IQ < 25µA
s Output Voltages from 1.19V to 9V
s Available in 24-Lead Narrow SSOP and 28-Lead
SSOP Packages
U
APPLICATIONS
s Notebook and Palmtop Computers, PDAs
s Cellular Telephones and Wireless Modems
s Portable Instruments
s Battery-Operated Devices
s DC Power Distribution Systems
DESCRIPTION
The LTC®1436A/LTC1437A are synchronous step-down
switching regulator controllers that drive external
N-channel power MOSFETs in a phase lockable, fixed
frequency architecture. The Adaptive PowerTM output stage
selectively drives two N-channel MOSFETs at frequencies
up to 400kHz while reducing switching losses to maintain
high efficiencies at low output currents.
An auxiliary 0.5A linear regulator using an external PNP
pass device provides a low noise, low dropout voltage
source. A secondary winding feedback control pin (SFB)
guarantees regulation regardless of the load on the main
output by forcing continuous operation.
An additional comparator is available for use as a low-
battery detector. A power-on reset timer (POR) is included
which generates a signal delayed by 65536/fCLK (300ms
typically) after the output is within 5% of the regulated
output voltage. Internal resistive dividers provide pin
selectable output voltages with remote sense capability.
The operating current level is user-programmable via an
external current sense resistor. Wide input supply range
allows operation from 3.5V to 30V (36V maximum).
, LTC and LT are registered trademarks of Linear Technology Corporation.
Adaptive Power is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
COSC
43pF
CSS
0.1µF
RC
10k
COSC
RUN/SS
VIN
TGL
TGS
CC
510pF
100pF
ITH
SGND
LTC1436A
SW
INTVCC
BOOST
VPROG
VOSENSE
SENSE –
BG
PGND
SENSE+
1000pF
VIN
4.5V TO 22V
M3
IRLML2803
DB
CMDSH-3
CB
0.1µF
M1
Si4412DY
L1
4.7µH
+
CIN
22µF
35V
×2
RSENSE
0.02Ω
+
4.7µF
M2
Si4412DY
D1
MBRS140T3
Figure 1. High Efficiency Step-Down Converter
R1
35.7k +
R2
102k
VOUT
1.6V
5A
COUT
100µF
6.3V
×2
1436 F01
1
1 page  
LTC1436A
LTC1436A-PLL/LTC1437A
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Input Voltage
VOUT = 3.3V
100
VOUT = 3.3V
95
ILOAD = 1A
90
85
ILOAD = 100mA
80
75
70
0
5 10 15 20 25 30
INPUT VOLTAGE (V)
1436 G01
VIN – VOUT Dropout Voltage
vs Load Current
0.5
RSENSE = 0.033Ω
VOUT DROP OF 5%
0.4
0.3
0.2
0.1
Efficiency vs Input Voltage
VOUT = 5V
100
VOUT = 5V
95
ILOAD = 1A
90
ILOAD = 100mA
85
80
75
70
0
5 10 15 20 25 30
INPUT VOLTAGE (V)
1436 G02
Load Regulation
0
– 0.25
RSENSE = 0.033Ω
– 0.50
– 0.75
–1.00
–1.25
Efficiency vs Load Current
100
VIN = 10V
95 VOUT = 5V
90 RSENSE = 0.033Ω
85
80
CONTINUOUS
MODE
75 Burst ModeTM
OPERATION
70
65
Adaptive Power
60 MODE
55
50
0.001
0.01 0.1
1
LOAD CURRENT (A)
10
1435 G03
VITH Pin Voltage vs Output Current
3.0
2.5
2.0
1.5
Burst Mode
OPERATION
1.0
CONTINUOUS/Adaptive
Power MODE
0.5
0
0 0.5 1.0 1.5 2.0 2.5 3.0
LOAD CURRENT (A)
1436 G04
Input Supply Current
vs Input Voltage
2.5
100
2.0 80
1.5
VOUT = 5V
EXTVCC = VOUT
60
1.0 VOUT = 3.3V
EXTVCC = OPEN
40
0.5 20
SHUTDOWN
00
0 5 10 15 20 25 30
INPUT VOLTAGE (V)
1436 G07
Burst Mode is a trademark of Linear Technology Corporation.
–1.50
0
0.5 1.0 1.5 2.0 2.5 3.0
LOAD CURRENT (A)
1436 G05
INTVCC Regulation
vs INTVCC Load Current
0.5
VEXTVCC = 0V
0.3
70°C
0
25°C
– 0.3
– 0.5
0
5 10 15
INTVCC LOAD CURRENT (mA)
20
1436 G08
0
0 10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (%)
1436 G06
EXTVCC Switch Drop
vs INTVCC Load Current
200
180
160 70°C
140
120 25°C
100
– 55°C
80
60
40
20
0
0 2 4 6 8 10 12 14 16 18 20
INTVCC LOAD CURRENT (mA)
1436 G09
5
5 Page 
U
OPERATIO (Refer to Functional Diagram)
Power-On Reset
The POR pin is an open drain output which pulls low when
the main regulator output voltage is out of regulation.
When the output voltage rises to within 7.5% of regula-
tion, a timer is started which releases POR after 216
(65536) oscillator cycles. In shutdown, the POR output is
pulled low.
Auxiliary Linear Regulator
The auxiliary linear regulator in the LTC1436A/LTC1437A
controls an external PNP transistor for operation up to
500mA. An internal AUXFB resistive divider set for 12V
operation is invoked when AUXDR pin is above 9.5V to
allow 12V VPP supplies to be easily implemented. When
AUXDR is below 8.5V an external feedback divider may be
used to set other output voltages. Taking the AUXON pin
low shuts down the auxiliary regulator providing a conve-
nient logic controlled power supply.
LTC1436A
LTC1436A-PLL/LTC1437A
The AUX block can be used as a comparator having its
inverting input tied to the internal 1.19V reference. The
AUXDR pin is used as the output and requires an external
pull-up to a supply less than 8.5V in order to inhibit the
invoking of the internal resistive divider.
INTVCC/DRVCC/EXTVCC Power
Power for the top and bottom MOSFET drivers and most
of the other LTC1436A/LTC1437A circuitry is derived from
the INTVCC pin. The bottom MOSFET driver supply DRVCC
pin is internally connected to INTVCC in the LTC1436A and
externally connected to INTVCC in the LTC1437A. When
the EXTVCC pin is left open, an internal 5V low dropout
regulator supplies INTVCC power. If EXTVCC is taken above
4.8V, the 5V regulator is turned off and an internal switch
is turned on to connect EXTVCC to INTVCC. This allows the
INTVCC power to be derived from a high efficiency external
source such as the output of the regulator itself or a
secondary winding, as described in the Applications Infor-
mation section.
APPLICATIONS INFORMATION
The basic LTC1436A application circuit is shown in Figure
1, High Efficiency Step-Down Converter. External compo-
nent selection is driven by the load requirement, and
begins with the selection of RSENSE. Once RSENSE is
known, COSC and L can be chosen. Next, the power
MOSFETs and D1 are selected. Finally, CIN and COUT are
selected. The circuit shown in Figure 1 can be configured
for operation up to an input voltage of 28V (limited by the
external MOSFETs).
RSENSE Selection For Output Current
RSENSE is chosen based on the required output current.
The LTC1436A/LTC1437A current comparator has a maxi-
mum threshold of 150mV/RSENSE and an input common
mode range of SGND to INTVCC. The current comparator
threshold sets the peak of the inductor current, yielding a
maximum average output current IMAX equal to the peak
value less half the peak-to-peak ripple current ∆IL.
Allowing a margin for variations in the LTC1436A/
LTC1437A and external component values yields:
RSENSE
=
100mV
IMAX
The LTC1436A/LTC1437A work well with RSENSE values
≥ 0.005Ω.
COSC Selection for Operating Frequency
The LTC1436A/LTC1437A use a constant frequency
architecture with the frequency determined by an external
oscillator capacitor COSC. Each time the topside MOSFET
turns on, the voltage on COSC is reset to ground. During the
on-time, COSC is charged by a fixed current plus an
additional current which is proportional to the output
voltage of the phase detector VPLLLPF (LTC1436A-PLL/
LTC1437A). When the voltage on the capacitor reaches
1.19V, COSC is reset to ground. The process then repeats.
The value of COSC is calculated from the desired operating
frequency. Assuming the phase-locked loop has no exter-
nal oscillator input (VPLLLPF = 0V):
11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTC1436AIGN-PLL.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LTC1436AIGN-PLL | High Efficiency Low Noise Synchronous Step-Down Switching Regulators | 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 |