XC9128_1 Datasheet, PDF (10/13 Pages) Torex Semiconductor – 1A Driver Transistor Built-In, Step-Up DC/DC Converters

XC9128/XC9129 Series
■NOTE ON USE (Continued)
7. P-ch synchronous switching transistor operation
The parasitic diode of the P-ch synchronous transistor is placed between Lx (anode) and V_OUT (cathode), so that the
power line can not be turned off from Lx to V_OUT. On the other hand, the power line switch from V_OUT to Lx is shown in the
table below.
●XC9128 Series
EN Pin
H
H
L
L
AEN/Pin
H
L
H
L
P-channel Synchronous Switch Transistor Operation
OFF
Switching
OFF
Undefined
●XC9129 Series
EN Pin
H
L
P-channel Synchronous Switch Transistor Operation
Switching
Undefined
With the XC9128B/XC9129B series, when step-up operation stops as a result of the latch condition working when the
maximum current limit level is reached, the synchronous P-channel transistor will remain ON.
8. The maximum current limiter controls the limit of the N-channel driver transistor by monitoring current flow. This function
does not limit the current flow of the P-channel synchronous transistor.
9. The integral latch time of the XC9128B/XC9129B series could be released from the maximum current detection state as a
result of board mounting conditions. This may extend integral latch time or the level required for latch operation to
function may not be reached. Please connect the output capacitor as close to the IC as possible.
10. With the XC9128B/XC9129B series, when the EN pin is left open or applied in the range of 0.2V～0.65V, the integral
latch or the V_LVP may not be able to release. Please make sure that the EN pin voltage is less than 0.2V or more than
0.65V, or use the XC9128D/XC9129D series which does not have the integral latch and the LVP functions.
11. With the XC9128B/XC9129B series, please make the V_OUT pin voltage become more than 1.5V within the soft-start time,
otherwise the V_LVP is detected. Also, the operation may become unstable, please test and verify the operation in the
actual circuits thoroughly before use.
12. When used in small step-up ratios, the device may skip pulses during PWM control mode.
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