2
DEMO MANUAL DC290
NO-DESIGN SWITCHER
SYMBOL PARAMETER
CONDITIONS
JUMPER POSITION
VALUE
I
Q
Burst Mode Operation Enabled
V
IN
= 5V, SYNC/MODE = RUN = 5V, I
OUT
= 0mA
JP1 = JP2 = L, JP3 = “1.5V”
10
µ
A (Note 3)
Supply Current
Pulse Skipping Mode Supply Current
V
IN
= 5V, SYNC/MODE = 0V, RUN = 5V, I
OUT
= 0mA
JP1 = U, JP2 = L
230
µ
A
Shutdown Current
V
IN
= 5V, RUN = 0V
JP2 = U
<1
µ
A
I
OUT
Maximum Output Current
V
IN
= 5V, V
OUT
= 2.5V (LTC1877)
JP2 = L, JP3 = “1.5V”
600mA
V
IN
= 4V, V
OUT
= 2.5V (LTC1878)
JP2 = L, JP3 = “1.5V”
600mA
f
OSC
Operating Frequency
Unsynchronized
JP2 = L
550kHz
Synchronized
JP1 = OPEN, JP2 = L
400kHz to 700kHz
V
RIPPLE
Typical Output Ripple
I
OUT
= 600mA, V
IN
= 5V, V
OUT
= 2.5V
JP2 = L, JP3 = “2.5V”
20mV
P-P
V
OUT
Typical Load Regulation
0mA < I
OUT
< 0.6A, V
IN
= 5V, SYNC/MODE = 0V
JP1 = U, JP2 = L
0.3%
V
SYNC
Synchronize Threshold Voltage
All
1.2V
V
RUN
Minimum Shutdown Threshold Voltage
All
0.4V
PACKAGE A D SCHE ATIC DIAGRA S
M
W
U
W
NOTE 1: JP1 and JP2 connect RUN (E1) and SYNC/MODE (E7) to either
GND (E3) or V
IN
(E2). When JP1 or JP2 is in the lower position (L), then
RUN or SYNC/MODE is connected to V
IN
. Alternatively, if JP1 or JP2 is in
the upper position (U), then RUN or SYNC/MODE is connected to GND. If
external sources drive RUN or SYNC/MODE, then JP1, JP2 or both must
be removed.
PERFOR A CE SU ARY
U
W
WW
NOTE 2: Programmable via optional R7. V
OUT
= 0.8V(1+ 887k
Ω
/R7)
NOTE 3: With V
IN
= 5V, the external feedback resistor contributes 0.24
µ
A
with JP3 = “1.5V” selected, 0.95
µ
A with JP3 = “2.5V” selected and 1.85
µ
A
with JP3 = “3.3V” selected.
Figure 1. LTC1877/LTC1878 Constant Frequency, High Efficiency Converter
1
2
3
4
RUN
I
TH
V
FB
GND
8
7
6
5
PPL LPF
SYNC/MODE
V
IN
SW
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
LTC187XEMS8
OPTIONAL
RUN
I
TH
V
FB
V
IN
GND
PLL LPF
SYNC/MODE
SW
LTC187X
C
ITH
220pF
R2
C2
1
2
3
4
8
7
6
5
C1
0.01
µ
F
R1
10k
R3
887k
R4
1M
C
FW
20pF
L1
10
µ
H
+
R5
412k
R6
280k
R7*
OPTIONAL
JP3
1.5V
2.5V
3.3V
OPEN
C
OUT
47
µ
F
6.3V
C
OUT1
**
1
µ
F
CER
C
IN
***
CER
E2
V
IN
≤
10V (LTC1877)
≤
6V (LTC1878)
E7
SYNC/MODE
E6
V
OUT
E5
GND
E4
GND
E1
RUN
E3
GND
JP2
JP1
* SPACE PROVIDED FOR AN OPTIONAL RESISTOR TO PROGRAM A CUSTOM OUTPUT VOLTAGE. THE OUTPUT VOLTAGE MUST NOT EXCEED 3.3V.
** C
OUT1
IS AN OPTIONAL CAPACITOR TO FILTER OUT VERY HIGH FREQUENCY SWITCHING NOISE.
*** C
IN
= 10
µ
F FOR LTC1877 AND C
IN
= 22
µ
F FOR LTC1878