CS5112YDWF24 ONSEMI [ON Semiconductor], CS5112YDWF24 Datasheet - Page 7

• Manufacturer Part Number: CS5112YDWF24
• Description: 1.4 A Switching Regulator with 5.0 V, 100 mA Linear Regulator with Watchdog, RESET and ENABLE
• Manufacturer: ONSEMI [ON Semiconductor]

the same circuitry and issue a reset when the linear output
voltage is below the regulation limit. After V
the minimum specified value, RESET remains low for a
fixed period t
RESET
V
RESET
RESET
4.25 V
R(PEAK)
4.45 V
4.25 V
5.0 V
5.0 V
The RESET signal frequency is given by:
The Power On Reset (POR) and low voltage RESET use
V
Figure 9. The Power On Reset Time Interval (t
V
WDI
V
REG
V
Begins When V
LIN
LIN
LIN
Figure 10. RESET Signal Is Issued Whenever
Figure 8. Timing Diagram When WDI Fails to
Appear Within the Preset Time Interval, t
A: Watchdog waiting for low−going transition on WDI
B: RESET stays low for t
V
V
R(LO)
LIN
POR
t
POR
Falls Below 4.25 V (Typical)
as shown in Figures 9 and 10.
f RESET +
LIN
t
POR
Rises Above 4.45 V (Typical)
2(t WDI )
WDI
50% Duty
Cycle
1
time
t
POR
A
LIN
B
rises above
WDI
POR
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)
CS5112
7
contains an error amplifier with selectable feedback inputs,
a current sense amplifier, an adjustable oscillator and a 1.4 A
output power switch with antisaturation control. The
switching regulator and external components, connected in
a boost configuration, are shown in Figure 11.
V
switching supply’s control circuitry is powered through
V
transistor.
charge the capacitor on C
develop a voltage drop across the internal sense resistor
(R
the output of the current sense amplifier, which is compared
to the output of the error amplifier. The error amplifier
generates an output voltage which is proportional to the
difference between the scaled down output boost voltage
(V
Once the current sense amplifier output exceeds the error
amplifier’s output voltage, the output transistor is turned off.
transistor on time is transferred to the load when the output
transistor is turned off. The output transistor is turned back
on at the next rising edge of the oscillator. On a cycle by
cycle basis, the current mode controller in a discontinuous
mode of operation charges the inductor to the appropriate
amount of energy, based on the energy demand of the load.
Figure 12 shows the typical current and voltage waveforms
for a boost supply operating in the discontinuous mode.
Notes:
IN
LIN
The POR delay (t
The current mode PWM switching voltage regulator
The switching regulator begins operation when V
The output transistor turns on when the oscillator starts to
The energy stored in the inductor during the output
S
FB1
1. Refer to Figure 5 to determine oscillator frequency.
2. The switching regulator can be disabled by providing
3. The boost output voltage can be controlled
). This voltage drop produces a proportional voltage at
CURRENT MODE PWM SWITCHING CIRCUITRY
are raised above 5.0 V. V
. V
a logic high at the ENABLE input.
dynamically by the feedback select input. If select is
open, V
selected.
or V
IN
FB2
supplies the base drive to the switcher output
t POR + 1.353
) and the internal bandgap voltage reference.
FB2
is selected. If select is low, then V
POR
) is given by:
OSC
C Delay R BIAS
. The output current will
REG
is required since the
REG
FB1
and
is