XC6415 Series
■OPERATIONAL DESCRIPTION
<Output Voltage Control>
The voltage divided by resistors Rx1 and Rx2 is compared with the internal reference voltage by the error amplifier. The P-
channel MOSFET which is connected to the VOUT pin is then driven by the subsequent output signal. The output voltage at the
VOUT pin is controlled and stabilized by a system of negative feedback. The current limit circuit and short protect circuit operate
in relation to the level of output current. Further, the IC's internal circuitry can be shutdown via the EN pin's signal.
V
IN
-
+
Error
Amp1
Current
Limit
EN1
VR1
ON/OFF
Control
each
circuit
EN1
V
OUT1
EN1/
R11
R12
Rdischg
EN1/
Voltage
Reference
V
SS
-
+
Error
Amp2
Current
Limit
EN2
VR2
ON/OFF
Control
each
circuit
EN2
V
OUT2
EN2/
R21
R22
Rdischg
EN2/
Voltage
Reference
< XC6415BB Series >
<CL Auto-Discharge Function>
XC6415B, D, F, H series can quickly discharge the electric charge at the output capacitor (CL), when a low signal to the EN pin,
which enables a whole IC circuit put into OFF state, is inputted via the N-channel transistor located between the VOUT pin and
the VSS pin (cf. BLOCK DIAGRAM). The CL discharge resistance is set to 550Ω when VIN is 6.0V (TYP.) and VOUT is 4.0V (TYP.).
Moreover, discharge time of the output capacitor (CL) is set by the CL auto-discharge resistance (R) and the output capacitor
(CL). By setting time constant of a CL auto-discharge resistance value [R] and an output capacitor value (CL) as τ(τ=C x R), the
output voltage after discharge via the N channel transistor is calculated by the following formulas.
τ
V = VOUT x e –t/
,
or t=τln (VOUT(E) / V )
(V : Output voltage after discharge, VOUT(E) : Output voltage, t: Discharge time,
τ: CL auto-discharge resistance R×Output capacitor (CL) value C)
CL high-speed discharge function can be set by each regulator.
<Current Limiter, Short-Circuit Protection>
The XC6415 series includes a fold-back circuit, which aid the operations of the current limiter and circuit protection. When the
load current reaches the current limit level, the fold-back circuit operates and output voltage drops. As a result of this drop in
output voltage, output current also decreases. When the output pin is shorted, a current of about 20mA flows.
<EN Pin>
The IC's internal circuitry can be shutdown via the signal from the EN pin with the XC6415 series. In shutdown mode, output
at the VOUT pin will be pulled down to the VSS level via Rx1 & Rx2. However, as for the XC6415B, D, F, H series, the CL auto-
discharge resistor is connected in parallel to Rx1 and Rx2 while the power supply is applied to the VIN pin. Therefore, time until
the VOUT pin reaches the VSS level becomes short. The EN pin is CMOS input, but in case the EN pin with pulled down resistor,
the EN input current will be increase when the IC operates. Also, in case of the EN pin without pulled down resistor, the output
voltage becomes unstable when the EN pin is left open. If this IC is used with the correct output voltage for the EN pin, the logic
is fixed and the IC will operate normally. However, supply current may increase as a result of through current in the IC's internal
circuitry when medium voltage is input.
■NOTES ON USE
1. Please use this IC within the stated absolute maximum ratings. The IC is liable to malfunction should the ratings be
exceeded.
2. Where wiring impedance is high, operations may become unstable due to noise and/or phase lag depending on output
current. Please wire the input capacitor (CIN) and the output capacitor (CL) as close to the IC as possible.
3. Torex places an importance on improving our products and its reliability.
However, by any possibility, we would equest user fail-safe design and post-aging treatment on system or equipment.
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