LTC2901-4CGN#PBF Linear Technology, LTC2901-4CGN#PBF Datasheet - Page 14

• Manufacturer Part Number: LTC2901-4CGN#PBF
• Description: IC MONITOR QUAD SUPP PROG 16SSOP
• Manufacturer: Linear Technology
• Type: Multi-Voltage Supervisorr

Specifications of LTC2901-4CGN#PBF

• Number Of Voltages Monitored: 4
• Output: Push-Pull, Totem Pole
• Reset: Active Low
• Reset Timeout: 5 ms Minimum
• Voltage - Threshold: 16 Selectable Threshold Combinations
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Voltage Supervisor Type: Voltage Monitor
• Number Of Voltage Supervisors: 4
• Operating Supply Voltage (min): 1V
• Package Type: SSOP N
• Operating Temperature Classification: Commercial
• Operating Temp Range: 0C to 70C
• Pin Count: 16
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LTC2901
Monitoring Power Supply Controller Activity
Figure 7 demonstrates how the LTC2901 can be used to
monitor switcher activity. The monitor is configured to
supervise 3.3V, 2.5V, 1.8V and one adjustable input.
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
unconnected, the watchdog time-out is approximately
200μs. 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
14
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
W
®
operation. With an
M1
R5
0.15Ω
D1
10μH
L1
U
+
C1
10μF
10V
C2
47μF
6V
R3
100k
R4
80.6k
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.
Ensuring Reset Valid for V
(LTC2901-2/LTC2901-4)
Some applications require the reset output (RST) to be
valid with V
handle this requirement with the addition of an external
resistor from RST to ground. The resistor will provide a
path for stray charge and/or leakage currents, preventing
the RST output from floating to undetermined voltages
when connected to high impedance (such as CMOS logic
inputs). The resistor value should be small enough to
provide effective pull-down without excessively loading
the active pull-up circuitry. Too large a value may not pull
down well enough. A 100k resistor from RST to ground is
satisfactory for most applications.
Burst Mode is a registered trademark of Linear Technology Corporation.
V
3.3V
V
1.8V
0.5A
IN
OUT
CC
71.5k
down to 0V. The LTC2901-2 is designed to
28k
1%
1%
R1
R2
14
13
12
11
10
4
3
8
V1
V2
V3
V4
WDI
V
V
GND
REF
PG
LTC2901-2
CC
COMP1
COMP2
COMP3
COMP4
Down to 0V
WDO
CWT
RST
CRT
2
16
1
15
6
7
5
9
3.3V MONITOR
1.8V MONITOR
FEEDBACK MONITOR
COMMON RESET OUT
LOW LOAD INDICATOR
2901 F07
C
47nF
RT
2901fb