AP3503 power management chip
The AP3503 is a step-down converter for current mode. They can
to drive 2A/3A loads with high power conversion efficiency
rate, as well as very good linear adjustment rate and load regulation rate.
The AP3502/3 features cycle-by-cycle current protection, programmable soft-start,
Short circuit protection and over-temperature protection functions, these functions are effectively improved
System reliability. The AP3502/3 is a synchronous step-down with a built-in power MOSFET switch
Transformer. The two MOSFETs alternately conduct to achieve the chopper input power
voltage, compare the current sensing signal with the EA output signal
Same adjustment of output voltage and MOSFET switching duty cycle. AP3502/3
There are also built-in circuit modules such as OCP, OVP, OTP and UVLO to Improve system reliability. For more description information, please refer to
Functional block diagram of the AP3502/3 (Figure 1). The AP3502/3 allows users to set the CSS by adjusting the capacity value
System soft start time. When the system starts, the IC is constant at 6μA
Constant current charges the CSS, producing a linearly increasing level signal,
This signal feeds back to the inverting side of the EA, and the voltage of the COMP is changed by this
signal clamping to achieve soft start of the system. This capacitor can
Calculate with the following formula:
FB
SS SS V
C t A 6μ = ×
Among them, CSS is the capacitor connected to the SS side, and tSS is the soft start
The time required to move, VFB is the feedback voltage.
2.2 Overcurrent protection
The AP3502/3 has built-in overcurrent protection circuitry to prevent cores
Accidental damage to the tablet. The AP3502/3 detects the upper-end MOSFET leakage
The current from the pole to the source, when the current exceeds 3.5A/5.6A,
OCP protection is triggered, and the top tube is forced to shut down until the next one
The arrival of the switch cycle.
FORMAT ONL
2.3 Short circuit protection
Since the voltage on the FB pin is directly proportional to the output voltage, when the output
When the outlet is shorted, the voltage on the FB is below 0.3V, which triggers
Short circuit protection function, the system operating frequency is reduced to 90kHz to protect it
IC。 When the short circuit is removed, the AP3502/3 will restart.
2.4 Overvoltage protection
The AP3502/3 has built-in overvoltage protection circuitry. When the power is output
When the voltage is higher than the protection voltage setting threshold, the power switch tube is all turned off
Break. When the overvoltage is removed, the AP3502/3 will restart.
2.5 Over-temperature protection
The AP3502/3 has built-in over-temperature protection circuitry to prevent IC junction temperature
High. When the junction temperature exceeds 16°C, the IC shuts down the internal controls
Circuit and power MOSFETs for protection functions. When the temperature is over-temperature
When removed and the junction temperature drops below 130°C, the AP3502/3 is reused
Initiate.
VIN=12V
C1
10 F/25V
(10 F/25V x2)
C2
22μF/6.3V x2
R4
100k
C4
0.1μF C6
Optional
C3
3.3nF
(3.9nF)
R3
2.2k
(6.8k)
D1
Optional
R1 26.1k
R2
10k
L1