1
DESCRIPTION
Demonstration Circuit DC1589A is a Linear Supercap Charger with Current-Limited Ideal Diode and V/I Monitor,
featuring the LTC
®
4425.
PERFORMANCE SUMMARY
Specifications are at T
A
= 25°C
SYMBOL PARAMETER
CONDITIONS
MIN TYP
MAX
UNITS
Vin
Input Voltage Range
2.7
5.5
V
Icharge Supercap
Charge
current
2
A
VOUT
Supercap Stack Output Voltage
1.2
5.4
V
V(MID)
Supercap Midpoint Voltage
0.6
2.7
V
QUICK START PROCEDURE
Refer to Figure 1 for the proper measurement
equipment setup and jumper settings and follow the
procedure below.
NOTE.
When measuring the input or output voltage ripple, care
must be taken to avoid a long ground lead on the oscilloscope
probe. Measure the input or output voltage ripple by touching the
probe tip directly across the VBUS or VOUT(x) and GND terminals.
See Figure 2 for proper scope probe technique.
1.
Set b[2-0] jmpers (JP3, JP4, JP5) to “1”. Set
MODE (JP6) to “LDO”. Set LD1 to 0A, and PS1
to 5V. Observe VOUT (VM3) = 3.3V, I(VIN)
(AM1) = 2A, and V(PROG) (VM2) = 1V. Note:
The supercapacitor COUT1 will charge in ap-
proximately 0.5 seconds, so please observe
these signals within a few seconds of setting
PS1 to 5V.
2.
Set PS1 to 0V. Observe D1 (PFO) should be lit
due to input ‘power failure’
3.
Set LD1 to 1A. Observe VOUT. VOUT should
decrease to 0V, in about 1 second.
QUICK START GUIDE
FOR DC1589A
LTC4425EDD: Linear Supercap
Charger With Current-Limited
Ideal Diode And V/I Monitor