DC826C - Demo Manual

DEMO MANUAL
DC826C-A/DC826C-B
LTC2950-2/LTC2951-2
Pushbutton On/Off Controller
DESCRIPTION
Demonstration circuits 826C-A and 826C-B feature the
LTC®2950-2 and the LTC2951-2 respectively, which are
low power, wide input voltage range, pushbutton on/off
controllers. A pushbutton switch shorts the PB pin to
ground which in turn sets the EN pin low (see Note 1).
Shorting PB to ground a second time subsequently resets
the EN pin high. The EN pin is used to connect to a DC/
DC converter shutdown to control the turn on and off of
the circuit, simulated with a green LED on the DC826C-A/
DC826C-B.
JP1 and JP2 on the DC826C-A provide the selection
of timing options for the PB on and off times. For the
DC826C-B, JP1 selects KILL times while JP2 selects off
times. JP3 ties and unties KILL to INT for immediate or
delayed turn off. The INT status is shown with a red LED.
DC826C-A/DC826C-B accepts an input voltage range of
2.7V to 26.4V or a 9V battery for portable demonstration
and evaluation.
Note 1: The inversion of EN of the LTC2950-2/LTC2951-2
is found in the LTC2950-1/LTC2951-1. Table 1 provides
an IC selection guide.
Design files for this circuit board are available at
http://www.linear.com/demo/DC826C
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.
IC SELECTION GUIDE
Table 1. LTC2950/LTC2951 Selection Guide (Typical Timing Values, Cap. Adjust = 212ms on DC826C-A/DC826C-B)
PART
ENABLE ONT
OFFT
KILLT
DEMO BOARD
LTC2950-1
EN
32ms + Cap. Adjust*
32ms + Cap. Adjust*
1000ms
N/A
LTC2950-2
EN
32ms + Cap. Adjust*
32ms + Cap. Adjust*
1000ms
DC826C-A
LTC2951-1
EN
128ms
32ms + Cap. Adjust*
128ms + Cap. Adjust*
N/A
LTC2951-2
EN
128ms
32ms + Cap. Adjust*
128ms + Cap. Adjust*
DC826C-B
*The additional Cap. Adjust time is selected by an external capacitor. The DC826C-A and DC826C-B adjust times have been pre-selected with a 0.033μF
capacitor to provide an additional 212ms. The additional time is calculated with the following equations as shown in the LTC2950/LTC2951 data sheets:
CONT = 1.56e-4 [μF/ms] • (tONT – 1ms)
COFFT = 1.56e-4 [μF/ms] • (tOFFT – 1ms)
CKILLT = 1.56e-4 [μF/ms] • (tKILL, OFF DELAY, ADDITIONAL – 1ms)
dc826cf
1
DEMO MANUAL
DC826C-A/DC826C-B
QUICK START PROCEDURE
Demonstration circuit 826C-A/826C-B is easy to set up to
evaluate the performance of the LTC2950-2/LTC2951-2:
2.Connect the input power supply of 2.7V to 26.4V across
VIN and GND or a 9V battery to the battery connector.
1.Place jumpers in the following positions:
3.Push and hold the pushbutton once to turn on the green
LED.
JP1:0.033μF
JP2:0.033μF
JP3:UNTIE
4.Push and hold the pushbutton again to turn off the
green LED.
OPERATING PRINCIPLES
The duration that PB must be shorted to ground in order
to turn on/off the DC/DC converter is independently programmed (LTC2950-2) by two external capacitors C1 and
C2 and selected on the DC826C-A with jumper JP1 and
JP2. The status of the EN pin, and simulation of the turn
on/off of a DC/DC converter, is displayed with green LED
D2 on the board.
Figure 1 shows how the EN is connected to the SHDN pin
of a DC/DC converter and how INT and KILL interfaces with
a µP or µC. An internal 500ms timer blanks (ignores) the
KILL signal during system power up. This allows sufficient
time for the DC/DC converter and a µP to perform power
up tasks. During turn off, a power down timer provides
a delay (LTC2950-2: 1000ms, LTC2951-2: adjustable)
from interrupting the µP (INT = low) to turning off the DC/
DC converter (EN = high). This delay gives the µP time
to perform power down and housekeeping tasks. On the
DC826C-B, JP1 selects the power down timer, while JP2
is used to adjust the turn off PB duration. The red LED
D1 shows the state of the INT pin. A µP can turn off the
converter with no delay by asserting KILL low. By tying
KILL to INT through JP3, KILL is forced low during the
INT blanking time and thus forces a turn off.
2
The RC (RRPP and CRPP) at VIN on the DC826 provides
reverse polarity protection to the LTC2950-2/LTC2951‑2. If
power is connected in an application such that the polarities are ensured to be in the correct configuration, this RC
may be removed from the circuit.
An additional RC (RF and CF), located at the PB pin, acts
as a filter and is used in an application where the switch
is located far from the LTC2950-2/LTC2951-2. In such a
case, the RC would be placed next to the switch rather
than the part. If the switch is located near the LTC2950-2/
LTC2951-2, then the RC may be removed from the circuit.
An LDO (U2) is used on the DC826 to provide a pull-up
voltage of 2.6V which is well below the absolute maximum
on the INT, EN, and KILL pins for the full range of input
voltage of 2.7V to 26.4V. In an application, pull these
pins up to a voltage no higher than their rated absolute
maximum shown in the data sheet. Optional Zener diodes
(D3 – D5) can be used if the pull-up voltage exceeds the
rated absolute maximum. (If the interface pins on the
DC826C-A /DC826C-B will be pulled up to an external
supply, LEDs D1 and D2 should be removed.)
dc826cf
DEMO MANUAL
DC826C-A/DC826C-B
OPERATING PRINCIPLES
PUSHBUTTON
VIN
VOUT
DC/DC
BUCK
VIN
2.7V TO 26.4
OR
9V BATTERY
SHDN
R1
10k
INT
µP/µC
KILL
DC826C F01
Figure 1. DC826C-A/DC826C-B Example Setup
dc826cf
3
1
2
3
4
BLK
GND
TP7
TP4
S1
ON/OFF
5.1k
RF
1k
VIN
2.7V-26.4V
PB
RRPP
VIN
TP1
CF
0.1uF
50V
CRPP
0.1uF
50V
A
B
1
JP1
OPEN
VIN
CUSTOMER NOTICE
JP2
C2
0.033uF
0.033uF
D3
11V
(Opt)
SEE NOTE #1
3
1
NC
IN
C:\PADS PROJECTS\826C-A\SCH\826C-A_REV1.DSN
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
C
D1
RED
2V
INT
R1
100
ADJ
4
5
UNTIE
PCB DES.

SCALE = NONE
D
APP ENG. Dilian Reyes
R5
100k
1%
R4
113k
1%
2.6V
IC NO.
E
SHEET
1
OF
1
1
REV.



MODIFY DATE: 

SIZE
DATE
Jan 27, 2014

 www.linear.com


TP6
GND
KILL
TP5
TP3
EN
TP2
INT
E

TECHNOLOGY
C4
0.47uF
10V
R3
100k
TITLE: SCHEMATIC
JP3
3
2
D2
GRN
2V
EN
R2
100
INT/KILL
1
TIE
APPROVALS
2
GND
OUT
Dilian Reyes
REVISION HISTORY
APPROVED
DESCRIPTION
D
PRODUCTION(Replaced S1, D1 & D2)
2.6V
D5
11V
(Opt)
C
U2
LT3014BES5
D4
11V
(Opt)

ECO REV
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
C1
0.033uF
8
6
5
OFFT
KILL
EN
3
OPEN
C
INT
2
PB
VIN
3
2
1
U1
LTC2950CTS8-2
ONT/KILLT
1
0.033uF
2
NOTE 1. EN, the inverse of EN,
is available in the LTC2950-1/LTC2951-1.
KEYSTONE
#232
RED
B
GND
4
ONT/KILLT
3
OFFT
4
7
A
1
2
3
4
DEMO MANUAL
DC826C-A/DC826C-B
SCHEMATIC DIAGRAM
dc826cf
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
1
2
3
4
BLK
GND
TP7
TP4
S1
ON/OFF
5.1k
RF
1k
VIN
2.7V-26.4V
PB
RRPP
VIN
TP1
CF
0.1uF
50V
CRPP
0.1uF
50V
A
B
1
JP1
OPEN
VIN
CUSTOMER NOTICE
JP2
C2
0.033uF
0.033uF
D3
11V
(Opt)
SEE NOTE #1
3
1
NC
IN
C:\PADS PROJECTS\826C-B\SCH\826C-B_REV1.DSN
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
C
D1
RED
2V
INT
R1
100
ADJ
4

SCALE = NONE
D
APP ENG. Dilian Reyes
PCB DES.
APPROVALS
2
GND
OUT
R5
100k
1%
R4
113k
1%
2.6V
IC NO.
E
SHEET
1
OF
1
1
REV.



MODIFY DATE: 

SIZE
DATE
Jan 27, 2014

 www.linear.com


TP6
GND
KILL
TP5
TP3
EN
TP2
INT
E

TECHNOLOGY
C4
0.47uF
10V
R3
100k
TITLE: SCHEMATIC
JP3
3
2
D2
GRN
2V
EN
R2
100
INT/KILL
1
TIE
UNTIE
5
Dilian Reyes
REVISION HISTORY
APPROVED
DESCRIPTION
D
PRODUCTION(Replaced S1, D1 & D2)
2.6V
D5
11V
(Opt)
C
U2
LT3014BES5
D4
11V
(Opt)

ECO REV
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
C1
0.033uF
8
6
5
OFFT
KILL
EN
3
OPEN
C
INT
2
PB
VIN
3
2
1
U1
LTC2951CTS8-2
ONT/KILLT
1
0.033uF
2
NOTE 1. EN, the inverse of EN,
is available in the LTC2950-1/LTC2951-1.
KEYSTONE
#232
RED
B
GND
4
ONT/KILLT
3
OFFT
7
A
1
2
3
4
DEMO MANUAL
DC826C-A/DC826C-B
SCHEMATIC DIAGRAM
dc826cf
5
DEMO MANUAL
DC826C-A/DC826C-B
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
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ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
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arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
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customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application
engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
6
dc826cf
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