XC9116
Series
■OPERATIONAL
EXPLANATIONS (Continued)
<Current Limit>
The current limit circuit of the XC9116 series monitors the current flowing through the N-channel MOS driver transistor
connected to the Lx pin, and features a combination of the constant-current type current limit mode and the duty cycle
limit of the next pulse.
1When
the driver current is greater than a specific level, the constant-current type current limit function operates to
turn off the pulses from the Lx pin at any given timing.
2The
IC controls the next pulse to be smaller than the first pulse.
Current Limit
Current Limit
I
L
L
X
①
The current w ill be of f w hen the coil current
reaches the value of the constant current limit.
②
Limit some duty pulses af ter the
limit.
<Lx Overvoltage Limit Circuit>
XC9116B series' Lx overvoltage limit circuit monitors the Lx pin voltage. When the Lx pin voltage exceeds than 19V
(TYP.), the IC performs the function of latching the OFF state of the driver transistor, and goes into operation suspension
mode. In suspension mode, operations can be resumed by restoring power to the V
IN
pin. The suspension mode
does not mean a complete shutdown, but a state in which pulse output is suspended; therefore, the internal circuitry
remains in operation.
<Maximum Duty Cycle Limit>
The XC9116B series' maximum duty cycle limit circuit monitors the duty cycle. When the maximum duty cycle is
repeated for a certain time, the IC controls the error amplifier output so that the duty cycle of the next pulse becomes
smaller than that of the first pulse.
<CE Pin Function>
The operation of the XC9116 series will enter into the shut down mode when a low level signal is input to the CE pin.
During the shut down mode, the supply current is 0
µ
A (TYP.), with high impedance at the Lx pin. The IC starts its
operation with a high level signal to the CE pin. The input to the CE/MODE pin is a CMOS input and the sink current is
0
µ
A (TYP.). 100
µ
s after disable, the IC goes into suspension mode and supply current is minimal. After this, the IC will
be in stand-by mode and the supply current will be 0
µ
A (TYP.).
■NOTES
ON USE
<Lx (Pin 1): Switch Pin>
Please connect the anode of a Schottky barrier diode and an inductor to the Lx pin.
<FB (Pin 3): Voltage Feedback Pin>
The reference voltage is 200mV (TYP.). A resistor (R
LED
) should be connected to the FB pin for setting the cathode of
LEDs and a constant current value. The resistance value can be calculated by the following equation.
R
LED
=0.2 / I
LED
I
LED
=Setting
constant current value
Typical example:
I
LED
5mA
10mA
R
LED
40
Ω
20
Ω
I
LED
13.3mA
20mA
R
LED
15
Ω
10
Ω
<CE (Pin 4): Chip Enable Pin>
An ENABLED state is reached when the CE voltage exceeds 0.65V and a DISABLED state when the CE Voltage falls
below 0.2V.
<V
IN
(Pin 5): Power Supply Pin>
Please connect an inductor and an input by-pass capacitor (C
IN
) to the V
IN
pin.
6/22
TOREX [ TOREX SEMICONDUCTOR ]
