XC6503 Datasheet, PDF (8/26 Pages) Torex Semiconductor – CL Capacitor-Less 500mA Low Power Consumption High Speed LDO Regulator

XC6503 Series
■ OPERATIONAL EXPLANATION
The voltage divided by resistors R1 and R2 is compared with the internal reference voltage by the error amplifier. The
P-channel MOSFET which is connected to the V_OUT pin is then driven by the subsequent output signal. The output voltage at the
V_OUT pin is controlled and stabilized by a system of negative feedback. The current limit circuit and short circuit protection operate
in relation to the level of output current and heat dissipation. Current limit circuit and short protection circuit operate with output
current and thermal shutdown circuit will operate with heating. Further, the IC’s internal circuitry can be shutdown via the CE pin
signal.
XC6503 Series D Type
<C_L Auto-Discharge Function>
XC6503D can quickly discharge the electric charge at the output capacitor (C_L), when a low signal to the CE pin, which enables
a whole IC circuit put into OFF state, is inputted via the N-channel transistor located between the V_OUT pin and the V_SS pin (cf.
BLOCK DIAGRAM). The C_L discharge resistance is set to 430Ω when V_IN is 6.0V (TYP.) and V_OUT is 5.0V (TYP.). Moreover,
discharge time of the output capacitor (C_L) is set by the C_L auto-discharge resistance (R_DCHG) and the output capacitor (C_L). By
setting time constant of a C_L auto-discharge resistance value (R_DCHG) and an output capacitor value (C_L) as τ(τ=C x R), the
output voltage after discharge via the N-channel transistor is calculated by the following formula.
V = V_{OUT x} e ^–t/τ, or ｔ=τln (V_OUT(E) / V)
( V : Output voltage after discharge, V_OUT(E) : Initial Output voltage, t: Discharge time,
τ: C_L auto-discharge resistance R_DCHG×C_L Output capacitance
<Current Limiter, Short-Circuit Protection>
The protection circuit operates as a combination of an output current limiter and fold-back short circuit protection. When load
current reaches the current limit level, the output voltage drops. As a result, the load current starts to reduce with showing
fold-back curve. The output current finally falls at the level of 120mA when the V_OUT pin is short-circuited.
<Thermal Shutdown>
When the junction temperature of the built-in driver transistor reaches the temperature limit, the thermal shutdown circuit
operates and the driver transistor will be set to OFF. The IC resumes its operation when the thermal shutdown function is
released and the IC’s operation is automatically restored because the junction temperature drops to the level of the thermal
shutdown release voltage.
<CE Pin>
The IC's internal circuitry can be shutdown via the signal from the CE pin with the XC6503D series. In shutdown mode, output
at the V_OUT pin will be pulled down to the V_SS level via R1, R2 and C_L auto-discharge resistance R_DCHG. Please note the
XC6503P does not have the CE pin.
The XC6503D has a pulled down resistor at the CE pin in order to avoid an unstable operation with the CE pin open (the CE
pin is left open, operation will be stopped). However, the CE pin input current will increase slightly through the pulled down
resistor when operating. If the correct output voltage is applied to the CE pin, the logic is fixed and the IC will operate normally.
However, if the medium voltage is input, supply current may increase as a result of an internal through current.
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