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PDF AS1325 Data sheet ( Hoja de datos )

Número de pieza AS1325
Descripción Step-Up DC-DC Converter
Fabricantes austriamicrosystems 
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AS1325
300mA Step-Up DC-DC Converter
Data Sheet
1 General Description
The AS1325 is a high-efficiency step-up DC-DC con-
verter designed to generate a fixed output voltage of
+3.3V or +5V.
The AS1325 achieves an efficiency of up to 96% and the
minimum input voltage is 1.5V. The AS1325-BSTT-33
delivers up to 300mA output current at the fixed output
voltage of +3.3V (@ 2V VBATT). With the fixed output
voltage of +5V the AS1325-BSST-50 supplies up to
185mA output current (@ 2V VBATT).
In order to save power the AS1325 features a shutdown
mode, where it draws less than 1µA. In shutdown mode
the battery is connected directly to the output enabling
the supply of real-time-clocks.
The AS1325 provides a power-on reset output that goes
high-impedance when the output reaches 90% of its reg-
ulation point.
The SHDNN trip threshold of the AS1325 can be used
as an input voltage detector that disables the device
when the battery voltage falls to a predetermined level.
An internal synchronous rectifier is included.
The AS1325 is available in a 6-pin SOT23 package.
Figure 1. Application Diagram
2 Key Features
! Fixed Output Voltage:
- 3.3V (AS1325-BSTT-33) or 5V (AS1325-BSST-50)
! Output Current:
- Up to 300mA (AS1325-BSTT-33) @ 2V VBATT
- Up to 185mA (AS1325-BSST-50) @ 2V VBATT
! Internal Synchronous Rectifier
! Shutdown Mode Supply Current: Less Than 1µA
! Efficiency: Up to 96%
! Minimum Input Voltage: +1.5V
! Accurate Shutdown Low-Battery Cutoff Threshold
! Battery Input Connected to Pin OUT in Shutdown
Mode for Backup Power
! Antiringing Control Minimizes EMI
! Ripple Reduction at Light Loads
! 6-pin SOT23 Package
3 Applications
The AS1325 is ideal for low-power applications where
ultra-small size is critical as in medical diagnostic equip-
ment, hand-held instruments, pagers, digital cameras,
remote wireless transmitters, cordless phones, and PC
cards. The device is also perfect as a local supply or as
a battery backup.
2
BATT
+1.5 to +3.3V or
+1.5 to +5.0V
Battery
CIN
22µF
L1
10µH
4
LX
On 1
Off SHDNN
+5.0V Output only
5
OUT
COUT
22µF
AS1325
6
RESETN
+3.3 or
+5.0V
Output
R1
100kΩ
RESETN
Output
3
GND
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AS1325 pdf
AS1325
Data Sheet - Electrical Characteristics
2. Voltage which triggers next loading cycle. Ripple and rms value depend on external components.
5.0V Output
TAMB = -40 to +85ºC, VBATT = +2V, VOUT = +5.0, VSHDNN = +1.5V (unless otherwise specified). Typ values @ TAMB = +25ºC.
Table 4. Electrical Characteristics
Parameter
Battery Input Range
Startup Battery Input Voltage 1
Output Voltage 2
N-Channel
On-Resistance
P-Channel On-Resistance
Light Load N-Channel Switch
Current Limit
N-Channel Switch Current Limit 1
Switch Maximum
On-Time
P-Channel Minimum On-Time
Synchronous Rectifier
Zero-Crossing Current
Quiescent Current into OUT
Shutdown Current into OUT
Shutdown Current into BATT
SHDNN Logic Low 1
SHDNN Threshold
SHDNN Threshold Hysteresis
RESETN Threshold
RESETN Voltage Low
RESETN Leakage Current
LX Leakage Current
Maximum Load Current
Efficiency
Symbol
Conditions
VBATT
RLOAD = 100Ω, TAMB = +25ºC
VSU
RLOAD = 100Ω, TAMB = -40 to +85ºC
VOUT
TAMB = +25ºC
TAMB = -40 to +85ºC
RNCH
ILX = 100mA, TAMB = +25ºC
ILX = 100mA, TAMB = -40 to +85ºC
RPCH
ILX = 100mA, TAMB = +25ºC
ILX = 100mA, TAMB = -40 to +85ºC
IMAX
tON
TAMB = +25ºC
TAMB = -40 to +85ºC
TAMB = +25ºC
TAMB = -40 to +85ºC
TAMB = +25ºC
TAMB = -40 to +85ºC
VOUT = +5.5V, TAMB = +25ºC
VOUT = +5.5V, TAMB = -40 to +85ºC
VSHDNN = 0V, TAMB = +25ºC
VSHDNN = 0V, TAMB = -40 to +85ºC
VSHDNN = 0V, TAMB = +25ºC
VSHDNN = 0V, TAMB = -40 to +85ºC
VBATT = +1.5 to +5.0V
Rising Edge, TAMB = +25ºC
Rising Edge, TAMB = -40 to +85ºC
ILOAD
η
Falling Edge, TAMB = +25ºC
Falling Edge, TAMB = -40 to +85ºC
IRESETN = 1mA, VOUT = +2.5V,
TAMB = +25ºC
IRESETN = 1mA, VOUT = +2.5V,
TAMB = -40 to +85ºC
VRESETN = +5.5V, TAMB = +25ºC
VRESETN = +5.5V, TAMB = +85ºC
TAMB = +25ºC
TAMB = +85ºC
VBATT = +2V
VBATT = +3V, ILOAD = 100mA
Min
1.5
4.950
4.875
550
450
5
4
8
0
1.185
1.170
4.288
4.242
Typ
1.22
1.24
5.000
0.3
0.4
400
700
7
1
30
35
0.01
0.01
1.228
0.02
4.500
0.1
1
0.1
10
185
91
Max
5.0
1.5
5.050
5.125
1.2
1.5
1.3
1.6
850
950
9
10
60
65
55
60
1
2
1
2
0.3
1.271
1.286
4.712
4.758
0.15
0.2
100
1000
Unit
V
V
V
Ω
Ω
mA
mA
µs
µs
mA
µA
µA
µA
V
V
V
V
V
nA
nA
mA
%
1. Guaranteed by design.
2. Voltage which triggers next loading cycle. Ripple and rms value depend on external components.
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AS1325 arduino
AS1325
Data Sheet - Detailed Description
Shutdown
When pin SHDNN is low the AS1325 is switched off and no current is drawn from battery; when pin SHDNN is high the
device is switched on. If SHDNN is driven from a logic-level output, the logic high-level (on) should be referenced to
VOUT to avoid intermittently switching the device on.
Note: If pin SHDNN is not used, it should be connected directly to pin OUT.
In shutdown the battery input is connected to the output through the inductor and the internal synchronous rectifier P-
FET. This allows the input battery to provide backup power for devices such as an idle microcontroller, memory, or real-
time-clock, without the usual diode forward drop. In this way a separate backup battery is not needed.
In cases where there is residual voltage during shutdown, some small amount of energy will be transferred from pin
OUT to pin BATT immediately after shutdown, resulting in a momentary spike of the voltage at pin BATT. The ratio of
CIN and COUT partly determine the size and duration of this spike, as does the current-sink ability of the input device.
Low-Battery Cutoff
The AS1325 SHDNN trip threshold (1.228V) can be used as an input voltage detector that disables the device when
the battery input voltage falls to a pre-set level. An external resistor-divider network can be used to set the battery-
detection voltage (see Figure 28).
Figure 28. Low-Battery Cutoff Application Diagram
+1.5 to +3.3V or
+1.5 to +5.0V
Battery
CIN
22µF
R1
220kΩ
R2
1MΩ
L1
10µH
10nF
2
BATT
4
LX
1
SHDNN
+5.0V Output only
AS1325
5
OUT
R3
100kΩ
6
RESETN
3
GND
COUT
22µF
+3.3V or +5.0V
Output
Power-On
Reset
For the resistor-divider network shown in Figure 28, calculate the value for R1 by:
R1 = R2 x ((VOFF/VSHDNN) - 1)
Where:
VOFF is the battery voltage at which the AS1325 shuts down.
VSHDNN = 1.228V
The value of R2 should be between 100kΩ and 1MΩ to minimize battery drain.
(EQ 1)
Note: Input ripple can cause false shutdowns, therefore to minimize the effect of ripple, a low-value capacitor from
SHDNN to GND should be used to filter out input noise. The value of the capacitor should be such that the R/C
time constant is > 2ms.
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