Agamem Microelectronics Inc.
PRELIMINARY
(Continued)
Parameter
Symbol
V
OH1
V
OH2
Output voltage
Output section
Output source
current
Output sink current
Pull down resistance
Pin voltage
Output current
setting section/
Control section
Input off condition
Input on condition
Pin current range
Stand-by current
Entire device
Average supply
current
V
OL1
V
OL2
I
O+
I
O –
R
O
V
CTL
I
OFF
I
ON
I
CTL
I
CCS
I
CC
—
R
B
= 390
Ω
AA1700
Constant Current White LED driver
Value
Min
Typ
1.2
1.0
0.1
0.1
–30
60
30
0.3
—
—
—
—
5.5
Max
—
—
0.2
0.2
–20
—
40
0.4
0
–45
–0.1
1
9.3
V
V
V
V
mA
mA
kΩ
V
µ
A
µ
A
mA
µ
A
mA
1.0
0.8
—
—
—
30
20
0.2
–20
—
–1.8
—
—
Unit
Condition
R
B
= 390
Ω
, I
O
= –15 mA
R
B
= 750
Ω
, V
CC
= 1.8 V
I
O
= –10 mA
R
B
= 390
Ω
, I
O
= 15 mA
R
B
= 750
Ω
, V
CC
= 1.8 V
I
O
= 10 mA
R
B
= 390
Ω
, V
O
= 0.9 V
R
B
= 390
Ω
, V
O
= 0.3 V
—
CTL pin open or V
CC
R
B
= 390
Ω
■
HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION
1. Soft Start
A soft start function, which gradually increases the width of the output pulses at power on, will be applied if a
capacitor is connected to the SP pin. This can prevent rush currents and overshoot when the power supply is
turned on.
Soft start time can be measured by the following equation. (The time until the output ON duty reaches
approximately 50%)
t
S
[s] = 0.35
×
C
PE
[uF]
2. Timer Latch Short Circuit Protection
When the load conditions suddenly change due to load effect, the short-circuit protection comparator outputs the
+
high-level signal (V
OM
) and the capacitor C
PE
connected to the SP terminal starts charging. When the external
capacitor C
PE
has been charged to approximately 0.8V, the latch circuit is set, the output terminal is fixed to low
level, and the dead-time is set to 100%. However, the latch circuit is not reset unless the power for the latch
circuit is turned off or restarted by the on/off control.
• Short circuit detection time
t
PE
[s] = 0.8
×
C
PE
[uF]
©Copyright
Agamem Microelectronics Inc.
5
www.agamem.com.tw
2007/1/22
AGAMEM [ AGAMEM MICROELECTRONIC INC. ]
