LTC2901 Linear Technology, LTC2901 Datasheet - Page 13

• Manufacturer Part Number: LTC2901
• Description: Programmable Quad Supply Monitor with Adjustable Reset and Watchdog Timers
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
Because 2.5V does not exist in this application, the V2
input is tied to the V1 (3.3V) input. The feedback voltage
on the LTC1772 (0.8V typ) is monitored with the adjust-
able input (V4). The RST pin will go high 216ms
(C
feedback voltage are above threshold. Individual input
status is available at the COMPX pins.
While the voltage monitors can detect low voltage or
shorted inputs, the watchdog circuit can be used to detect
an open circuit to the primary load. With the CWT pin
TYPICAL APPLICATIO S
RT
C1: TAIYO YUDEN CERAMIC LMK325BJ106K-T
C2: SANYO POSCAP 6TPA47M
D1: MOTOROLA MBRM120T3
L1: COILTRONICS UP1B-100
M1: Si3443DV
R5: DALE 0.25W
= 47nF) after the 3.3V and 1.8V supplies and the
R6
10k
C3
220pF
1
2
3
I
GND
V
Figure 7. Monitor Input, Output, Feedback Voltage and Low Load Conditions on DC/DC Controller
TH
FB
LTC1772
U
SENSE
PGATE
V
IN
–
U
6
5
4
U
W
Quad Supply Monitor with Watchdog Timer Disabled
M1
SYSTEM
R5
0.15
D1
RESET
C
RT
10 H
1.8V
L1
5V
U
5V, 3V, 1.8V, 12V (ADJ)
+
1
2
3
4
5
6
7
8
C1
10 F
10V
C2
47 F
6V
COMP3
COMP1
V3
V1
CRT
RST
WDO
WDI
LTC2901
R3
100k
R4
80.6k
COMP2
COMP4
unconnected, the watchdog time-out is approximately
200 s. At low load currents on the 1.8V supply, the
LTC1772 will go into Burst Mode
open-ciruit load, the duty cycle at the gate of M1 will drop,
and the pulse spacing will exceed the watchdog time-out
period. The WDO pin will go low indicating the low load
condition. The WDO pin will return high on the next pulse
to the gate of M1. The WDO pin will remain high if the load
is restored.
Burst Mode is a registered trademark of Linear Technology Corporation.
CWT
V
GND
V
REF
V2
V4
PG
V
3.3V
V
1.8V
0.5A
IN
OUT
16
15
14
13
12
11
10
9
3V
2901 TA02
R4
100k
1%
71.5k
2.15M
28k
1%
1%
1%
R3
R1
R2
12V
V
TRIP
14
13
12
11
10
4
3
8
= 11.25V
V1
V2
V3
V4
WDI
V
V
GND
REF
PG
LTC2901-2
COMP1
COMP2
COMP3
COMP4
WDO
CWT
RST
CRT
®
2
16
1
15
6
7
5
9
operation. With an
3.3V MONITOR
1.8V MONITOR
FEEDBACK MONITOR
COMMON RESET OUT
LOW LOAD INDICATOR
2901 F07
LTC2901
C
47nF
RT
2901is sn2901
13