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PDF PAM2312 Data sheet ( Hoja de datos )
| Número de pieza | PAM2312 | |
| Descripción | 1A STEP-DOWN DC-DC CONVERTER | |
| Fabricantes | Diodes | |
| Logotipo |  |
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A Product Line of
Diodes Incorporated
PAM2312
1A STEP-DOWN DC-DC CONVERTER
Description
The PAM2312 is a step-down current-mode, DC-DC converter. At
heavy load, the constant frequency PWM control performs excellent
stability and transient response. To ensure the longest battery life in
portable applications, the PAM2312 provides a power-saving
Pulse- Skipping Modulation (PSM) mode to reduce quiescent current
under light load operation to save power.
The PAM2312 supports a range of input voltages from 2.5V to 5.5V,
allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/NiMH
cell, USB, and other standard power sources. The output voltage is
adjustable from 0.6V to the input voltage, while the part number suffix
PAM2312-XX indicates pre-set output voltage of 3.3V, 2.8V, 2.5V,
1.8V, 1.5V, 1.2V or adjustable. All versions employ internal power
switch and synchronous rectifier to minimize external part count and
realize high efficiency. During shutdown, the input is disconnected
from the output and the shutdown current is less than 1µA. Other key
features include under-voltage lockout to prevent deep battery
discharge.
The PAM2312 is available in TSOT25 packages.
Features
• Efficiency up to 96%
• Only 40µA (typ) Quiescent Current
• Output Current: Up to 1A
• Internal Synchronous Rectifier
• 1.5MHz Switching Frequency
• Soft Start
• Under-Voltage Lockout
• Short Circuit Protection
• Thermal Shutdown
• 5-pin Small TSOT25 Packages
• Pb-Free Package
Pin Assignments
Top View
TSOT25
Applications
• Cellular Phone
• Portable Electronics
• Wireless Devices
• Cordless Phone
• Computer Peripherals
• Battery Powered Widgets
• Electronic Scales
• Digital Frame
Typical Applications Circuit
Fixed Output Voltage
Adjustable Output Voltage
PAM2312
Document number: DSxxxxx Rev. 2 - 0
1 of 14
www.diodes.com
VO
=
0.6x⎜⎛1 +
⎝
R1
R2
⎟⎞
⎠
January 2013
© Diodes Incorporated
1 page  
A Product Line of
Diodes Incorporated
PAM2312
Typical Performance Characteristics (@TA = +25°C, CIN = 10µF, CO = 10µF, L = 4.7µH, unless otherwise specified.)
PAM2312
Document number: DSxxxxx Rev. 2 - 0
5 of 14
www.diodes.com
January 2013
© Diodes Incorporated
5 Page 
A Product Line of
Diodes Incorporated
PAM2312
Application Information (cont.)
For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to:
PD = IO 2 RDS(ON)H + IQ VIN
Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input
voltage range. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surrounding airflow
and temperature difference between junction and ambient. The maximum power dissipation can be calculated by the following formula:
PD = TJ(MAX) − TA
θJA
Where TJ(MAX) is the maximum allowable junction temperature +125°C. TA is the ambient temperature and θJA is the thermal resistance from the
junction to the ambient. Based on the standard JEDEC for a two layers thermal test board, the thermal resistance θJA of TSOT25 package is
250°C/W, DFN2X2 102°C/W, and QFN3X3 68°C/W, respectively. The maximum power dissipation at TA = +25°C can be calculated by following
formula:
PD = (125°C - 25°C) /250°C/W = 0.4W
Setting the Output Voltage
The internal reference is 0.6V (Typical). The output voltage is calculated as below:
The output voltage is given by Table 1.
VO
=
0.6x⎜⎛1
⎝
+
R1
R2
⎟⎞
⎠
Table 1: Resistor selection for output voltage setting.
VO
1.2V
1.5V
1.8V
2.5V
3.3V
R1
100k
150k
200k
380k
540k
R2
100k
100k
100k
120k
120k
100% Duty Cycle Operation
As the input voltage approaches the output voltage, the converter turns the P-channel transistor continuously on. In this mode the output voltage
is equal to the input voltage minus the voltage drop across the P-Channel transistor:
( )VOUT = VIN − ILOAD RDSON + RL
where RDS(ON) = P-Channel switch ON resistance, ILOAD = Output Current, RL = Inductor DC Resistance
UVLO and Soft-Start
The reference and the circuit remain reset until the VIN crosses its UVLO threshold. The PAM2312 has an internal soft-start circuit that limits the
in-rush current during start-up. This prevents possible voltage drops of the input voltage and eliminates the output voltage overshoot. The soft-
start acts as a digital circuit to increase the switch current in several steps to the P-channel current limit (1500mA).
Short Circuit Protection
The switch peak current is limited cycle-by-cycle to a typical value of 1500mA. In the event of an output voltage short circuit, the device operates
with a frequency of 500kHz and minimum duty cycle, therefore the average input current is typically 200mA.
Thermal Shutdown
When the die temperature exceeds +150°C, a reset occurs and the reset remains until the temperature decrease to +120°C, at which time the
circuit can be restarted.
PAM2312
Document number: DSxxxxx Rev. 2 - 0
11 of 14
www.diodes.com
January 2013
© Diodes Incorporated
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet PAM2312.PDF ] | |
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