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PDF LTC2938 Data sheet ( Hoja de datos )
| Número de pieza | LTC2938 | |
| Descripción | (LTC2938 / LTC2939) Configurable 4- and 6-Supply Monitors | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC2938/LTC2939
Configurable 4- and 6-Supply
Monitors with Watchdog Timer
FEATURES
n Simultaneously Monitors Four (LTC2938) or Six
Supplies (LTC2939)
n Sixteen User-Selectable Combinations of 5V, 3.3V,
2.5V, 1.8V, 1.5V, 1.2V and/or ± Adjustable Voltage
Thresholds
n Guaranteed Threshold Accuracy: ±1.5%
n Adjustable Reset and Watchdog Timeout
n Low Supply Current: 80μA Typical
n Power Supply Glitch Immunity
n Guaranteed RST for VCC > 1V
n High Temperature Operation to 125°C
n 12-Pin 4mm × 3mm DFN or 12-Lead MSOP
(LTC2938) and 16-Lead MSOP Package (LTC2939)
APPLICATIONS
n Desktop and Notebook Computers
n Multivoltage Systems
n Telecom Equipment
n Network Servers
n Automotive Control Systems
DESCRIPTION
The LTC®2938/LTC2939 are configurable supply monitors
for systems with up to four or six supply voltages that need
watchdog supervision. One of sixteen preset or adjustable
voltage monitor combinations can be selected using an
external resistive divider connected to the program input.
The preset voltage thresholds are accurate to ±1.5% over
temperature. The LTC2938 and LTC2939 also feature ad-
justable inputs with a 0.5V nominal threshold.
The reset and watchdog timeout periods are adjustable
using external capacitors. Tight voltage threshold accuracy
and glitch immunity ensure reliable reset operation without
false triggering. The RST output is guaranteed to be in the
correct state for VCC down to 1V. Each status output has
a weak internal pull-up and may be externally pulled up
to a user-defined voltage.
The 80μA supply current makes the LTC2938 and LTC2939
ideal for power conscious systems. The LTC2939 moni-
tors up to six supplies and the LTC2938 monitors up to
four supplies.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6967591, 7239251, 7119714.
TYPICAL APPLICATION
6-Supply Monitor 12V (ADJ), 5V, 3.3V, 2.5V, 1.8V, 1.2V (ADJ)
12V
5V
3.3V SYSTEM
2.5V LOGIC
1.8V
1.2V
0.1μF
0.1μF
2150k 124k
1% 1%
100k 100k
1% 1%
V1
V2
V3
V4
V5
V6
VREF
R1
59k
1%
VPG
GND
R2
40.2k
1%
LTC2939
WDI
WDO
RST
CWT
CWT
47nF
tRST = 94ms
CRT tWD = 940ms
CRT
47nF
293839 TA01
Voltage Configuration Table
V1 (V)
5
5
5
5
5
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
V2 (V)
3.3
3.3
3.3
3.3
3.3
2.5
2.5
1.8
1.8
1.8
2.5
2.5
1.8
1.8
1.5
1.2
V3 (V)
2.5
2.5
1.8
ADJ
ADJ
1.8
1.8
1.5
1.5
1.2
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
V4 (V)
1.8
ADJ
ADJ
ADJ
–ADJ
1.5
ADJ
1.2
ADJ
ADJ
ADJ
–ADJ
ADJ
–ADJ
ADJ
ADJ
V5 (V)
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
V6 (V)
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
293839ff
1
Free Datasheet http://www.datasheet-pdf.com/
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC2938/LTC2939
Supply Current vs Temperature
90
V1 = 5V
V2 = 3.3V
V3 = 2.5V
85
V4 = 1.8V
V5 = V6 = 1V
I(V4) vs V4 in –ADJ mode
–100μ
–10μ
–1μ
125°C
80
–100n
85°C
–10n
75
–1n 25°C
70
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
29389 G04
RST Pull-Up Current vs V2
18
TA = 25°C
15
–100p
–300 –250 –200 –150 –100
V4 (mV)
–50 0
29389 G05
RST Output Voltage vs V1,
VPG = GND
6
TA = 25°C
10k PULL-UP FROM RST TO V1
5 V1 = V2
12 4
9
VRT33
6 VRT25
VRT18
3 VRT15
VRT12
0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
V2 (V)
29389 G07
3
2
1
0
01
23
V1 (V)
45
29389 G08
Reset Timeout Period
vs Temperature
5 CRT = 1500pF
(SILVER MICA)
4
Watchdog Timeout Period vs CWT
100
TA = 25°C
10
1
3 100m
10m
2
1m
1
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
29389 G10
100μ
10p 100p
1n 10n
CWT (F)
100n 1μ
29389 G11
Transient Duration
vs Comparator Overdrive
400
TA = 25°C
350
300
250
200
RESET OCCURS
ABOVE CURVE
150
100
50
0
0.1 1
10 100
RESET COMPARATOR OVERDRIVE (% OF VRTX)
29389 G06
Watchdog Timeout Period
vs Temperature
36
CWT = 1500pF
(SILVER MICA)
34
32
30
28
26
24
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
29389 G09
Reset Timeout Period vs CRT
10
TA = 25°C
1
100m
10m
1m
100μ
10μ
10p 100p
1n 10n
CRT (F)
100n 1μ
29389 G12
293839ff
5
Free Datasheet http://www.datasheet-pdf.com/
5 Page 
LTC2938/LTC2939
APPLICATIONS INFORMATION
A less accurate supervisor increases the required system
voltage margin and increases the probability of system
malfunction. The LTC2938 and LTC2939 ±1.5% specifica-
tion improves the reliability of the system over supervisors
with wider threshold tolerances.
Monitor Configuration
Select the LTC2938/LTC2939 input voltage combination
by placing the recommended resistive divider from VREF
to GND and connect the tap point to VPG, as shown in
Figure 2.
Table 1 offers recommended 1% resistor values for the
various modes. The rightmost column in Table 1 specifies
optimum VPG / VREF ratios (±0.01), when configuring with
a ratiometric DAC.
Upon power-up, the LTC2938 or LTC2939 enters a con-
figuration period of approximately 150μs during which
the voltage on the VPG input is sampled and the monitor
is configured to the desired input combination. Do not
add capacitance to the VPG input. Immediately after
programming, the comparators are enabled and supply
monitoring begins.
LTC2938/
LTC2939
VREF
R1
1%
VPG R2
GND 1%
293839 F02
Figure 2. Monitor Programming
Table 1. Voltage Threshold Modes
MODE
V1 (V)
V2 (V)
0 5 3.3
1 5 3.3
2 3.3 2.5
3 3.3 2.5
4 3.3 1.8
5 5 3.3
6 5 3.3
7 3.3 1.8
8 3.3 1.8
9 3.3 1.8
10 3.3 2.5
11 3.3 2.5
12 3.3 1.8
13 3.3 1.5
14 5 3.3
15 3.3 1.2
V3 (V)
ADJ
ADJ
ADJ
ADJ
1.5
2.5
2.5
1.5
1.2
ADJ
1.8
1.8
ADJ
ADJ
1.8
ADJ
V4 (V)
ADJ
–ADJ
ADJ
–ADJ
ADJ
ADJ
1.8
1.2
ADJ
ADJ
1.5
ADJ
–ADJ
ADJ
ADJ
ADJ
R1 (kΩ)
Open
93.1
86.6
78.7
71.5
66.5
59
53.6
47.5
40.2
34.8
28
22.1
16.2
9.53
Short
R2 (kΩ)
Short
9.53
16.2
22.1
28
34.8
40.2
47.5
53.6
59
66.5
71.5
78.7
86.6
93.1
Open
VPG/VREF
0
0.094
0.156
0.219
0.281
0.344
0.406
0.469
0.531
0.594
0.656
0.719
0.781
0.844
0.906
1
293839ff
11
Free Datasheet http://www.datasheet-pdf.com/
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC2938.PDF ] | |
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