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Número de pieza | LM2622MM-ADJ | |
Descripción | 600kHz/1.3MHz Step-up PWM DC/DC Converter | |
Fabricantes | National Semiconductor | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de LM2622MM-ADJ (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
No Preview Available ! October 2001
LM2622
600kHz/1.3MHz Step-up PWM DC/DC Converter
General Description
The LM2622 is a step-up DC/DC converter with a 1.6A, 0.2Ω
internal switch and pin selectable operating frequency. With
the ability to convert 3.3V to multiple outputs of 8V, -8V, and
23V, the LM2622 is an ideal part for biasing TFT displays.
The LM2622 can be operated at switching frequencies of
600kHz and 1.3MHz allowing for easy filtering and low noise.
An external compensation pin gives the user flexibility in
setting frequency compensation, which makes possible the
use of small, low ESR ceramic capacitors at the output. The
LM2622 is available in a low profile 8-lead MSOP package.
n 600kHz/1.3MHz pin selectable frequency operation
n Over temperature protection
n 8-Lead MSOP package
Applications
n TFT Bias Supplies
n Handheld Devices
n Portable Applications
n GSM/CDMA Phones
n Digital Cameras
Features
n 1.6A, 0.2Ω, internal switch
n Operating voltage as low as 2.0V
Typical Application Circuit
600 kHz Operation
© 2001 National Semiconductor Corporation DS101273
10127331
www.national.com
1 page Electrical Characteristics (Continued)
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged
directly into each pin.
Note 4: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100%
production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to
calculate Average Outgoing Quality Level (AOQL).
Note 5: Typical numbers are at 25˚C and represent the most likely norm.
Note 6: Duty cycle affects current limit due to ramp generator.
Note 7: Current limit at 0% duty cycle. See TYPICAL PERFORMANCE section for Switch Current Limit vs. VIN
Note 8: Bias current flows into FB pin.
Note 9: Junction to ambient thermal resistance (no external heat sink) for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit.
See ’Scenario ’A’’ in the Power Dissipation section.
Note 10: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0191 sq. in. of copper heat sinking. See ’Scenario ’B’’ in the Power Dissipation section.
Note 11: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0465 sq. in. of copper heat sinking. See ’Scenario ’C’’ in the Power Dissipation section.
Note 12: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.2523 sq. in. of copper heat sinking. See ’Scenario ’D’’ in the Power Dissipation section.
Note 13: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0098 sq. in. of copper heat sinking on the top layer and 0.0760 sq. in. of copper heat sinking on the bottom layer, with three 0.020 in. vias connecting the planes.
See ’Scenario ’E’’ in the Power Dissipation section.
Typical Performance Characteristics
Efficiency vs. Load Current
(VOUT = 8V, fS = 600 kHz)
Efficiency vs. Load Current
(VOUT = 8V, fS = 1.3 MHz)
10127326
Switch Current Limit vs. Temperature
(VIN = 3.3V, VOUT = 8V)
10127325
Switch Current Limit vs. VIN
10127320
5
10127322
www.national.com
5 Page Operation (Continued)
The phase margin can also be improved by adding CC2 as
discussed earlier in the section. The equation for ADC is
given below with additional equations required for the calcu-
lation:
mc ) 0.072fs (in V/s)
where RL is the minimum load resistance, VIN is the maxi-
mum input voltage, gm is the error amplifier transconduc-
tance found in the Electrical Characteristics table, and RD-
SON is the value chosen from the graph ’RDSON vs. VIN ’ in
the Typical Performance Characteristics section.
Layout Considerations
The input bypass capacitor CIN, as shown in the typical
operating circuit, must be placed close to the IC. This will
reduce copper trace resistance which effects input voltage
ripple of the IC. For additional input voltage filtering, a 100nF
bypass capacitor can be placed in parallel with CIN, close to
the VIN pin, to shunt any high frequency noise to ground. The
output capacitor, COUT, should also be placed close to the
IC. Any copper trace connections for the COUT capacitor can
increase the series resistance, which directly effects output
voltage ripple. The feedback network, resistors RFB1 and
RFB2, should be kept close to the FB pin, and away from the
inductor, to minimize copper trace connections that can in-
ject noise into the system. Trace connections made to the
inductor and schottky diode should be minimized to reduce
power dissipation and increase overall efficiency. For more
detail on switching power supply layout considerations see
Application Note AN-1149: Layout Guidelines for Switching
Power Supplies.
11 www.national.com
11 Page |
Páginas | Total 16 Páginas | |
PDF Descargar | [ Datasheet LM2622MM-ADJ.PDF ] |
Número de pieza | Descripción | Fabricantes |
LM2622MM-ADJ | 600kHz/1.3MHz Step-up PWM DC/DC Converter | National Semiconductor |
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