TS3300

Page 10

TS3300 Rev. 1.0

prevent the collapse of the input voltage to the boost

regulator when the input is a weak (high impedance)

source. If the input voltage drops below a determined

voltage threshold (settable by a resistor divider), the

boost

regulator

switching

cycles

are

paused,

effectively

limiting

the

minimum

input

voltage.

capacitor at the boost’s output can service burst

loads, and the input source exhibits substantial

source impedance (such as with an old battery, or at

cold temperatures).

(BI FB) in conjunction with a voltage divider circuit

can be implemented as shown in Figure 4. The

feedback pin voltage is 392mV. It is recommended to

use large resistor values to minimize additional

current draw at the input.

Using the following equation to solve for R5 for a

given R6 value, the output voltage can be set:

R3=

V

ANTI-CRUSH

TM

- 0.392 R4

0.392

Ω,

R3 is calculated to be 1.78M

voltage is to be set above the minimum input voltage

specification of the TS3300.

Figure 5 shows a scope capture of the load step

response. The measurement was performed with the

Boost Regulator is pulsed with a 100mA load every

100ms for 1ms as shown by the pink curve, the input

voltage after a battery impedance of 10

Ω 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.

feature in action at start-up under a heavy capacitive

load of 500µF and an input source impedance of

10

Ω. A high source impedance is typical of a weak

battery source. The measurement was performed

and blue traces represent the input current and boost

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.

a Voltage Divider

Output Capacitor and a 10

Ω Input Impedance.

Regulation with Load Step Response