TS3300 Datasheet, PDF (13/14 Pages) Touchstone Semiconductor Inc – 0.6-4.5VIN, 1.8-5.25VOUT, 3.5-uA, Low Input Voltage, High-Efficiency Boost + LDO

Figure 7: Setting the Anti-Crush^TM Voltage
with a Voltage Divider
Using the following equation to solve for R5 for a
given R6 value, the output voltage can be set:
R5= ^{൫VANTI-CRUSHTM - 0.392൯R6}
0.392
To set a 0.8V output voltage with R6 = 1.37MΩ, R5 is
calculated to be 1.42MΩ. A 1% standard resistor
value of 1.37MΩ can be selected. This results in an
anti-crush voltage of 784mV. The anti-crush^TM
voltage is to be set above the minimum input voltage
specification of the TS3300.
Figure 5 shows a scope capture of the anti-crush^TM
feature in action at start-up under a heavy capacitive
Large Output Capacitor Start-up with Anti-Crush^TM at 0.9V
VBI=1.2V, ESR of VBI =10Ω, VBO=VREGIN=3V, VREGOUT=1.8V,
CBO=500µF, CREGOUT=10µF
TS3300
load of 500µF and an input source impedance of
10Ω. A high source impedance is typical of a weak
battery source. The measurement was performed
with the anti-crush^TM voltage set to 0.9V. The purple,
blue, and pink trace represent the input current, boost
output voltage, and LDO output voltage, respectively.
At start-up, the current rises up to 50mA and drops to
approximately 30mA for approximately 40ms in order
to charge the output capacitor. At this point, the
voltage to the input of the TS3300 is 0.9V until the
boost output achieves regulation and in turn, the LDO
output voltage achieves regulation as well.
Figure 6 shows a scope capture of the load step
response. The measurement was performed with the
anti-crush^TM voltage set to 0.9V. As the output of the
LDO is pulsed with a 100mA load every 100ms for
1ms as shown by the pink curve, the input voltage
after a battery impedance of 10Ω drops from 1.2V to
0.9V as shown by the blue curve and the boost
output voltage drops by only 160mV as shown by the
yellow curve. The TS3300 quickly replenishes the
500µF capacitor and the output of the boost regulator
returns to 3V. Note that the LDO remains regulated
and is unaffected by the load step.
Load Step Response with Anti-Crush^TM at 0.9V
VBI=1.2V, ESR of VBI =10Ω, VBO=VREGIN=3V, VREGOUT=1.8V,
CBO=500µF, CREGOUT=10µF, IREGOUT=100mA pulse
Figure
100ms/DIV
5: Using the Anti-Crush^TM Feature
under a Heavy Capacitive Load
(500µF) and a 10Ω Boost Input
Source Impedance at Start-up
2ms/DIV
Figure 6: Using the Anti-Crush^TM Feature to
Maintain Regulation of the Boost
Regulator and LDO Output Voltage
TS3300DS r1p0
Page 13
RTFDS