AIC1880 Ver la hoja de datos (PDF) - Analog Intergrations
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AIC1880 Datasheet PDF : 11 Pages
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AIC1880
COMPONENT SELECTION
VIN
VOUT
fOSC
(V) (V) (Hz)
L
(µH)
COUT
(µF)
RCOMP
(kΩ)
3.3
10
640k
10 (Taiyo Yuden 10 ceramic (Taiyo Yuden
NP06D B100M) EMK325BJ106MN-B)
39
3.3
10
1.2M
6.8 (Taiyo Yuden 10 ceramic (Taiyo Yuden
NP06D B6R8M) EMK325BJ106MN-B)
33
3.3
5
640k
10 (Taiyo Yuden 10¯2 ceramic (Taiyo Yu-
NP06D B100M) den EMK325BJ106MN-B)
30
3.3
5
1.2M
4.7 (Taiyo Yuden 10¯2 ceramic (Taiyo Yu-
NP06D B4R7M) den EMK325BJ106MN-B)
36
5.0
10
640k
10 (Taiyo Yuden 10¯2 ceramic (Taiyo Yu-
NP06D B100M) den EMK325BJ106MN-B)
30
5.0
10
1.2M
6.8 (Taiyo Yuden 10¯2 ceramic (Taiyo Yu-
NP06D B6R8M) den EMK325BJ106MN-B)
22
CCOMP
(pF)
820
1200
820
1000
1200
1500
CCOMP2
(pF)
20
TYPICAL
IOUT (MAX)
(mA)
250
20
250
10
700
20
700
20
500
56
500
APPLICATION INFORMATION
Operation
The AIC1880 is a fixed-frequency and high efficiency
step-up DC/DC converter with current-mode PWM
control architecture. By selecting appropriate circuit
components, it can achieve fast transient response.
The AIC1880 can regulate its output voltage through a
feedback control circuit, which is composed of an error
amplifier; two comparators and several control signal
generators. By comparing the voltage at FB pin to the
reference voltage of 1.24, the error amplifier varies the
voltage at COMP pin. The voltage at COMP pin is
compared with the summing signal of current sensing
signal and slope compensation signal to determine the
duty cycle of internal power switch. In order to prevent
overcharging the output capacitor and achieve better
efficiency, AIC1880 will enter pulse-skipping mode
(PSM) operation while working at light load conditions.
Frequency Selection
The AIC1880’s switching frequency can be selected to
be either 640kHz or 1.2MHz. The switching frequency
is 640kHz, while FREQ pin is connected to GND. The
switching frequency is 1.2MHz, as FREQ pin is con-
nected to VIN. For 640kHz operation, an internal
pull-low of FREQ pin allows the FREQ pin uncon-
nected.
Current Limitation
Current limitation function of AIC1880 will be activated
when the peak value of switch current reaches 1.6A
(typ.). While the current limitation function is activated,
the duty cycle will be reduced to limit the output power
to protect the internal power switch.
Soft-Start
The AIC1880 provides the soft-start function. When
SHDN pin is connected to VIN, an internal current
source of 4µA (typ.) charges an external soft-start ca-
pacitor. During the soft-start period, the voltage at SS
pin will decide the allowable peak value of switch cur-
rent. The peak value of switch current is 0A, when the
voltage at SS pin is 0V. In addition, it is in full current
limitation when the voltage at SS pin is higher than
1.0V. The soft-start time can be calculated in accor-
dance with the following equation.
7
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