CS5111 Datasheet, PDF (8/16 Pages) Cherry Semiconductor Corporation – 1.4A Switching Regulator with 5V, 100mA Linear Regulator with Watchdog, RESET and ENABLE

CS5111
V_IN
V_LIN
I_BIAS
R_BIAS
64.9 kΩ
C_OSC
Oscillator
V_REG
Overvoltage
COMP
COMP
Logic
Base Drive
V_SW
1.4 A
V_OUT
C_OUT
Current Sense Amplifier
+
–
R_S
GND
ENABLE
+
–
Switcher Shutdown
1.25 V
Bandgap
Reference
Switcher
Error
R₁
V_FB1
Amplifier
–
Multiplexer
V_FB2
R₂
+
R₃
SELECT
Figure 11. Block Diagram of the 1.4 A Current Mode Control Switching Regulator Portion of the
CS5111 in a Boost Configuration
V_SW
V_OUT
V_IN
V_SAT
0
I_SW
I_Peak
0
I_D
I_Peak
PROTECTION CIRCUITRY
If the input voltage at V_REG is increased above the
overvoltage threshold, the drive to the linear and switcher
output transistors is shut off. Therefore, V_LIN is disabled and
V_SW can not be pulled low.
The current out of V_LIN is sensed in order to limit
excessive power dissipation in the linear output transistor
over the output range of 0 V to regulation. Also, the current
t
into V_SW is sensed in order to provide the current limit
function in the switcher output transistor.
If the die temperature is increased above 160°C, either due
to excessive ambient temperature or excessive power
dissipation, the drive to the linear output transistor is
reduced proportionally with increasing die temperature.
t
Therefore, V_LIN will decrease with increasing die
temperature above 160°C. Since the switcher control
circuitry is powered through V_LIN, the switcher
performance, including current limit, will be affected by the
decrease in V_LIN.
0
t
Figure 12. Voltage and Current Waveforms
for Boost Topology in CS5111
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