|
|
PDF LTC1157 Data sheet ( Hoja de datos )
| Número de pieza | LTC1157 | |
| Descripción | 3.3V Dual Micropower High-Side/Low-Side MOSFET Driver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LTC1157 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
|
No Preview Available !
LTC1157
3.3V Dual Micropower
High-Side/Low-Side MOSFET Driver
FEATURES
s Allows Lowest Drop 3.3V Supply Switching
s Operates on 3.3V or 5V Nominal Supplies
s 3 Microamps Standby Current
s 80 Microamps ON Current
s Drives Low Cost N-Channel Power MOSFETs
s No External Charge Pump Components
s Controlled Switching ON and OFF Times
s Compatible with 3.3V and 5V Logic Families
s Available in 8-Pin SOIC
APPLICATI S
s Notebook Computer Power Management
s Palmtop Computer Power Management
s P-Channel Switch Replacement
s Battery Charging and Management
s Mixed 5V and 3.3V Supply Switching
s Stepper Motor and DC Motor Control
s Cellular Telephones and Beepers
DESCRIPTIO
The LTC1157 dual 3.3V micropower MOSFET gate driver
makes it possible to switch either supply or ground
reference loads through a low RDS(ON) N-channel switch
(N-channel switches are required at 3.3V because P-
channel MOSFETs do not have guaranteed RDS(ON) with
VGS ≤ 3.3V). The LTC1157 internal charge pump boosts
the gate drive voltage 5.4V above the positive rail (8.7V
above ground), fully enhancing a logic level N-channel
switch for 3.3V high-side applications and a standard N-
channel switch for 3.3V low-side applications. The gate
drive voltage at 5V is typically 8.8V above supply (13.8V
above ground), so standard N-channel MOSFET switches
can be used for both high-side and low-side applications.
Micropower operation, with 3µA standby current and
80µA operating current, makes the LTC1157 well suited
for battery-powered applications.
The LTC1157 is available in both 8-pin DIP and SOIC.
TYPICAL APPLICATI
Ultra Low Voltage Drop 3.3V Dual High-Side Switch
3.3V
+
10µF
3.3V
LOGIC
VS
IN1
(8.7V)
G1
LTC1157
(8.7V)
IN2 G2
GND
IRLR024
IRLR024
3.3V
LOAD
LTC1157 • TA01
3.3V
LOAD
Gate Voltage Above Supply
12
10
8
6
4
2
0
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
SUPPLY VOLTAGE (V)
LTC1157 • TA02
1
1 page  
UU W U
APPLICATIO S I FOR ATIO
MOSFET Selection
The LTC1157 is designed to operate with both standard
and logic level N-channel MOSFET switches. The choice of
switch is determined primarily by the operating supply
voltage.
Logic Level MOSFET Switches at 3.3V
Logic level switches should be used with the LTC1157
when powered from 2.7V to 4V. Although there is some
variation among manufacturers, logic level MOSFET
switches are typically rated with VGS = 4V with a maximum
continuous VGS rating of ±10V. RDS(ON) and maximum
VDS ratings are similar to standard MOSFETs and there is
generally little price differential. Logic level MOSFETs are
frequently designated by an “L” and are usually available
in surface mount packaging. Some logic level MOSFETs
are rated up to ±15V and can be used in applications which
require operation over the entire 2.7V to 5.5V range.
Standard MOSFET Switches at 5V
Standard N-channel MOSFET switches should be used
with the LTC1157 when powered from 4V to 5.5V supply
as the built-in charge pump produces ample gate drive to
fully enhance these switches when powered from a 5V
nominal supply. Standard N-channel MOSFET switches
are rated with VGS = 10V and are generally restricted to a
maximum of ±20V.
Powering Large Capacitive Loads
Electrical subsystems in portable battery-powered equip-
ment are typically bypassed with large filter capacitors to
reduce supply transients and supply induced glitching. If
not properly powered however, these capacitors may
themselves become the source of supply glitching.
For example, if a 100µF capacitor is powered through a
switch with a slew rate of 0.1V/µs, the current during start-
up is:
ISTART = C(dV/dt)
= (100 × 10 – 6) (1 × 10 5)
= 10A
LTC1157
Obviously, this is too much current for the regulator (or
output capacitor) to supply and the output will glitch by as
much as a few volts.
The start-up current can be substantially reduced by
limiting the slew rate at the gate of an N-channel switch as
shown in Figure 1. The gate drive output of the LTC1157
VIN LT1129-3.3
+
3.3µF
3.3V
ON/0FF
VS
IN1
G1
1/2 LTC1157
R1
100k
GND
R2
1k
MTD3055EL
C1 + CLOAD
0.1µF
100µF
3.3V
LOAD
LTC1157 • TA02
Figure 1. Powering a Large Capacitive Load
is passed through a simple RC network, R1 and C1, which
substantially slows the slew rate of the MOSFET gate to
approximately 1.5 × 10 –4 V/µs. Since the MOSFET is
operating as a source follower, the slew rate at the source
is essentially the same as that at the gate, reducing the
start-up current to approximately 15mA which is easily
managed by the system regulator. R2 is required to
eliminate the possibility of parasitic MOSFET oscillations
during switch transitions. Also, it is good practice to
isolate the gates of paralleled MOSFETs with 1k resistors
to decrease the possibility of interaction between switches.
Reverse Battery Protection
The LTC1157 can be protected against reverse battery
conditions by connecting a 300Ω resistor in series with
the ground pin. The resistor limits the supply current to
less than 12mA with – 3.6V applied. Since the LTC1157
draws very little current while in normal operation, the
drop across the ground resistor is minimal. The 3.3V µP
(or control logic) can be protected by adding 10k resistors
in series with the input pins.
5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LTC1157.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LTC1150 | +-15V Chopper Stabilized Operational Amplifier with Internal Capacitors | Linear Technology |
| LTC1151 | Dual +-15V Zero-Drift Operational Amplifier | Linear Technology |
| LTC1152 | Rail-to-Rail Input Rail-to-Rail Output Zero-Drift Op Amp | Linear Technology |
| LTC1153 | Auto-Reset Electronic Circuit Breaker | 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 |