LT1304-5.0V UTC, LT1304-5.0V Datasheet - Page 10

• Manufacturer Part Number: LT1304-5.0V
• Description: MICROPOWER DC/DC CONVERTERS
• Manufacturer: UTC

UTC LT1304/LT1304-3.3V/LT1304-5.0V
Low-Battery Detector
The LT1304 contains an independent low-battery detector that remains active when the device is shut down. This
detector, actually a hysteretic comparator, has an open collector output that can sink up to 500µA.The comparator
also operates below the switcher’s undervoltage lockout threshold, operating until V
1.4V.Figure 8 illustrates the input /output characteristic of the detector. Hysteresis is clearly evident in the figure.
Battery Life
How may hours does it work? This is the bottom line question that must be asked of any efficiency study. AA
alkaline cells are not perfect power sources. For efficient power transfer, energy must be taken from AA cells at a
rate that does not induce excessive loss. AA cells internal impedance, about 0.2 Ω fresh and 0.5 Ω end-of-life, results
in significant efficiency loss at high discharge rates. Figure 10 illustrates battery life vs load current of Figure 9’s
LT1304, 2-cell to 5V DC/DC converter. Note the accelerated decrease in hours at higher power levels. Figure 11
plots total watt hours vs load current. Watt hours are determined by the following formula:
WH = I
UTC
LOAD
(5V)(H)
Figure 7. Suggested Layout for Best Performance.Input Capacitor Placement as
Shown Is Highly Recommended.Switch Trace (pin 4) Copper Area Is Minimized
V
V
IN
OUT
UNISONIC TECHNOLOGIES CO., LTD.
2V/DIV
V
Figure 8. Low-Battery Detector Transfer Function.
Pull-Up R=22K,VIN=2V,Sweep Frequency=10Hz
LBO
LINEAR INTEGRATED CIRCUIT
GND (BATTERY AND LOAD RETURN)
+
C
OUT
1
2
3
4
200mV/DIV
LT1304
V
LBI
+
C
SHUTDOWN
IN
8
7
6
5
IN
reaches approximately
QW-R103-018,A
10