XC9264 Datasheet, PDF (15/30 Pages) Torex Semiconductor – 18V Operation 0.5A Synchronous Step-Down DC/DC Converters

XC9263/XC9264
Series
■NOTE ON USE
1) For the phenomenon of temporal and transitional voltage decrease or voltage increase, the IC may be damaged or deteriorated
if IC is used beyond the absolute MAX. specifications.
2) Make sure that the absolute maximum ratings of the external components and of this IC are not exceeded.
3) The DC/DC converter characteristics depend greatly on the externally connected components as well as on the characteristics of this IC,
so refer to the specifications and standard circuit examples of each component when carefully considering which components to select.
Be especially careful of the capacitor characteristics and use B characteristics (JIS standard) or X7R, X5R (EIA standard) ceramic
capacitors.
The capacitance decrease caused by the bias voltage may become remarkable depending on the external size of the capacitor.
4) If there is a large dropout voltage, then there might be pulse-skip during light loads even with PWM control.
5) The DC/DC converter of this IC uses a current-limiting circuit to monitor the coil peak current. If the potential dropout voltage is large or
the load current is large, the peak current will increase, which makes it easier for current limitation to be applied which in turn could cause
the operation to become unstable. When the peak current becomes large, adjust the coil inductance and sufficiently check the operation.
The following formula is used to show the peak current.
Peak Current: Ipk = (V_IN – V_OUT) × OnDuty / (2 × L × f_OSC) + I_OUT
L: Coil Inductance [H]
f_OSC: Oscillation Frequency [Hz]
I_OUT: Load Current [A]
6) If there is a large dropout voltage, a circuit delay could create the ramp-up of coil current with staircase waveform exceeding the current
limit.
7） The ripple voltage could be increased when switching from discontinuous conduction mode to Continuous conduction mode.
Please evaluate IC well on customer’s PCB.
8) The operation of the IC becomes unstable below the minimum operating voltage.
9) If the voltage at the EN/SS Pin does not start from 0V but it is at the midpoint potential when the power is switched on, the soft start function
may not work properly and it may cause the larger inrush current and bigger ripple voltages.
10) The effects of ambient noise and the state of the circuit board may cause release from the current limiting state, and the latch time may
lengthen or latch operation may not take place. Please evaluate IC well on customer’s PCB.
11) Instructions of pattern layouts
The operation may become unstable due to noise and/or phase lag from the output current when the wire impedance is high,
please place the input capacitor(C_IN) and the output capacitor (C_L) as close to the IC as possible.
(1) In order to stabilize V_IN voltage level, we recommend that a by-pass capacitor (C_IN) be connected as close as possible to the
V_IN and GND pins.
(2) Please mount each external component as close to the IC as possible.
(3) Wire external components as close to the IC as possible and use thick, short connecting traces to reduce the circuit impedance.
(4) Make sure that the GND traces are as thick as possible, as variations in ground potential caused by high ground currents at the
time of switching may result in instability of the IC.
(5) Please note that internal driver transistors bring on heat because of the load current and ON resistance of High-side driver transistor,
Low-side driver transistor
15/30