XC9519 TOREX [Torex Semiconductor], XC9519 Datasheet - Page 11

• Manufacturer Part Number: XC9519
• Description: Dual Output Step-Up/Inverting DC/DC Converter
• Manufacturer: TOREX [Torex Semiconductor]

■OPERATIONAL EXPLANATION (Continued)
< C
means of the internal switch between the VOUTP pin and AGND pin (between the VOUTN pin and AVIN pin).
equation for the output voltage discharge time can be obtained from the following CR discharge equation.
ｔ
V: Output voltage during discharge
V
t: Discharge time
τ: C
[Example]
discharge time t from the start of C
(*1) Calculated with I
<Internal OSC Timing Chart>
the step-up driver on timing for the DC/DC Converter is shifted to completely opposite position (180 degrees different) upon the phase of driver
on timing for the Inverting DC/DC Converter.
<Overvoltage Protection>
(V
pin voltage reaches the overvoltage protection detection voltage, the driver transistor of the step-up DC/DC converter (inverting DC/DC
converter) is turned off to hold down the rise of output voltage. When the output voltage falls after overvoltage protection detection, normal
DC/DC converter operation resumes.
V
[Example]
calculated as shown below.
<Load disconnect Control Circuit>
step-up DC/DC converter is in the standby state.
The Load disconnect control circuit makes it possible to break continuity between V
OUTSET
Overvoltage protection monitors the output voltage V
The output voltage V
OUTPSET
This function enables high-speed discharge of the charge on the output capacitor (C
This function makes it possible to prevent malfunctioning of applications caused by charge remaining on C
The discharge time is determined by the C
=
When the set voltage (V
ｔ
The step-up DC/DC Converter and the Inverting DC/DC Converter are switching synchronously based on one internal clock. The phase of
OUTN
V
In a step-up DC/DC converter with the indicated conditions, the output voltage V
L
τ
OUT_OVP P
=
Internal OSC
Condition: Output Voltage (V
V
Auto-Discharge Function >
L
ln
×R
τ
Inverting_I
OUT_OVPP
) from rising too far above the set voltage. In particular, fluctuations in the load cause the output voltage to rise, and when the FBP (FBN)
: Output voltage
（
ln ( V
(V
Boost_I
DCHG
V
OUTNSET
OUTSET
(V
OUTPSET
OUT_OVPN
= V
LX
LX
): Output voltage, V
/ V
OUTPSET
）
0A
0A
/ V )= C
OUT
)=V
OUT_OVP
= 0mA
× V
OUTPSET
OUTPSET
LP
OVP
that is detected by overvoltage protection is obtained from the following equation:
×R
= 5.0V × (1.0 + 0.07(TYP.)) =5.0V × 1.07 = 5.35V
DCHGP
OUTPSET
)=5.0V, C
(V
L
Inductor Peak Current
high-speed discharge until the output voltage falls to 1.0V can be calculated as follows:
OUTNSET
OVPP
ln ( V
)=5.0V, V
(V
) × V
OVPN
LP
OUTPSET
L
=18.8μF, and the C
discharge resistance (R
): Detect Overvoltage Protection Voltage
OVP P
Inductor Peak Current
OVPP
1.2MHz
/ V ) = 18.8
(V
=V
OVPN
OUTP
FBP
)
+0.07V(TYP.) , V
(V
μ
OUTN
F×200
L
) using the FBP (FBN) pin voltage, and prevents the output voltage V
discharge resistance (R
DCHC
Ω
×ln ( 5.0V / 1.0V ) = 6.05×10
) and C
FBP
=1.0V(TYP.)
IN
L
. Ifτ(τ= C
and V
OUT_OVPP
L
) when an L level signal is input to the ENP (ENN) pin by
OUTP
DCHGP
that is detected by overvoltage protection can be
by turning off the external P-ch MOS FET when the
L
× R
)=200Ω (TYP.) of the DC/DC Converter, the
DCHG
-3
) is the time constant of C
s = 6.05 ms
L
.
(*1)
L
and R
XC9519
11/38
DCHG
Series
OUTP
, the