Outputs. LQH3C220 Datasheet

LQH3C220 Datasheet PDF

Part LQH3C220
Description Dual Micropower DC/DC Converter with Positive and Negative Outputs
Feature LQH3C220; LT1945 Dual Micropower DC/DC Converter with Positive and Negative Outputs FEATURES s s DESCRIPTIO .
Manufacture Linear Technology
Datasheet
Download LQH3C220 Datasheet




LQH3C220
FEATURES
s Generates Well-Regulated Positive and
Negative Outputs
s Low Quiescent Current:
20µA in Active Mode (per Converter)
<1µA in Shutdown Mode
s Operates with VIN as Low as 1.2V
s Low VCESAT Switch: 250mV at 300mA
s Uses Small Surface Mount Components
s High Output Voltage: Up to ±34V
s Tiny 10-Pin MSOP Package
U
APPLICATIO S
s Small TFT LCD Panels
s Handheld Computers
s Battery Backup
s Digital Cameras
LT1945
Dual Micropower DC/DC
Converter with Positive and
Negative Outputs
DESCRIPTIO
The LT®1945 is a dual micropower DC/DC converter in a
10-pin MSOP package. Each converter is designed with a
350mA current limit and an input voltage range of 1.2V to
15V, making the LT1945 ideal for a wide variety of appli-
cations. Both converters feature a quiescent current of
only 20µA at no load, which further reduces to 0.5µA in
shutdown. A current limited, fixed off-time control scheme
conserves operating current, resulting in high efficiency
over a broad range of load current. The 36V switch allows
high voltage outputs up to ±34V to be easily generated
without the use of costly transformers. The LT1945’s low
off-time of 400ns permits the use of tiny, low profile
inductors and capacitors to minimize footprint and cost in
space-conscious portable applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
2.7V
TO 5V
C1
4.7µF
Dual Output (+12V, –20V) Converter
L1
10µH
C4
0.1µF
D1
8 10
VIN
2
SHDN1
SW1
1
NFB1
LT1945
4
SHDN2
5
FB2
GND PGND PGND SW2
37 96
D2
100pF 365k
24.9k
–20V
10mA
C2
1µF
115k
L2
10µH
C1: TAIYO YUDEN JMK212BJ475
C2, C3: TAIYO YUDEN TMK316BJ105
C4: TAIYO YUDEN EMK107BJ104
D1, D2, D3: ZETEX ZHCS400
L1, L2: MURATA LQH3C100
4.7pF
D3
C3
1M 1µF
12V
20mA
1945 TA01
Efficiency at VIN = 3.6V
90
85
+12V OUTPUT
80
–20V OUTPUT
75
70
65
60
55
50
0.1
1 10
LOAD CURRENT (mA)
100
1945 TA01a
1945f
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LQH3C220
LT1945
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, SHDN1, SHDN2 Voltage ................................... 15V
SW1, SW2 Voltage .................................................. 36V
NFB1 Voltage ........................................................... –3V
FB2 Voltage ...............................................................VIN
Current into NFB1 Pin ........................................... –1mA
Current into FB2 Pin .............................................. 1mA
Junction Temperature ........................................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
NFB1 1
SHDN1 2
GND 3
SHDN2 4
FB2 5
TOP VIEW
10 SW1
9 PGND
8 VIN
7 PGND
6 SW2
MS PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 160°C/W
ORDER PART
NUMBER
LT1945EMS
MS PART MARKING
LTTS
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VSHDN = 1.2V unless otherwise noted.
PARAMETER
CONDITIONS
Minimum Input Voltage
Quiescent Current, (per Converter)
NFB1 Comparator Trip Point
Not Switching
VSHDN = 0V
FB2 Comparator Trip Point
FB Comparator Hysteresis
NFB1, FB2 Voltage Line Regulation
NFB1 Pin Bias Current (Note 3)
FB2 Pin Bias Current (Note 4)
Switch Off Time, Switcher 1 (Note 5)
1.2V < VIN < 12V
VNFB1 = –1.23V
VFB2 = 1.23V
Switch Off Time, Switcher 2 (Note 5)
Switch VCESAT
Switch Current Limit
VFB2 > 1V
VFB2 < 0.6V
ISW = 300mA
SHDN Pin Current
SHDN Input Voltage High
VSHDN = 1.2V
VSHDN = 5V
SHDN Input Voltage Low
Switch Leakage Current
Switch Off, VSW = 5V
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1945 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the – 40°C to 85°C operating
MIN
q –1.205
q 1.205
q 1.3
q
250
0.9
TYP
20
–1.23
1.23
8
0.05
2
30
400
400
1.5
250
350
2
8
0.01
MAX
1.2
30
1
–1.255
1.255
0.1
2.9
80
350
400
3
12
0.25
5
UNITS
V
µA
µA
V
V
mV
%/V
µA
nA
ns
ns
µs
mV
mA
µA
µA
V
V
µA
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: Bias current flows out of the NFB1 pin.
Note 4: Bias current flows into the FB2 pin.
Note 5: See Figure 1 for Switcher 1 and Switcher 2 locations.
1945f
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LQH3C220
LT1945
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Saturation Voltage
(VCESAT)
0.60
0.55
0.50
0.45
ISWITCH = 500mA
0.40
0.35
0.30
ISWITCH = 300mA
0.25
0.20
0.15
0.10
–50 –25
0
25 50 75 100
TEMPERATURE (°C)
1945 G01
FB2 Pin Voltage and
Bias Current
1.25
1.24
VOLTAGE
1.23
1.22 CURRENT
1.21
1.20
–50 –25 0
25 50
TEMPERATURE (°C)
50
40
30
20
10
0
75 100
1945 G02
Switch Off Time
550
500
450
400 VIN = 1.2V
VIN = 12V
350
300
250
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1945 G04
Switch Current Limit
400
VIN = 12V
350
300
VIN = 1.2V
250
200
150
100
50
0
–50 –25 0
25 50 75
TEMPERATURE (°C)
100
1945 G05
NFB1 Pin Voltage and
Bias Current
–1.25
5
–1.24
–1.23
VOLTAGE
4
3
–1.22
–1.21
CURRENT
2
1
–1.20
–50
–25 0 25 50
TEMPERATURE (°C)
0
75 100
1945 G03
Quiescent Current
25
VFB = 1.23V
NOT SWITCHING
23
21
VIN = 12V
19
VIN = 1.2V
17
15
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1945 G06
PI FU CTIO S
NFB1 (Pin 1): Feedback Pin for Switcher 1. Set the output
voltage by selecting values for R1 and R2.
SHDN1 (Pin 2): Shutdown Pin for Switcher 1. Tie this pin
to 0.9V or higher to enable device. Tie below 0.25V to turn
it off.
GND (Pin 3): Ground. Tie this pin directly to the local
ground plane.
SHDN2 (Pin 4): Shutdown Pin for Switcher 2. Tie this pin
to 0.9V or higher to enable device. Tie below 0.25V to turn
it off.
FB2 (Pin 5): Feedback Pin for Switcher 2. Set the output
voltage by selecting values for R1B and R2B.
SW2 (Pin 6): Switch Pin for Switcher 2. This is the
collector of the internal NPN power switch. Minimize the
metal trace area connected to the pin to minimize EMI.
PGND (Pins 7, 9): Power Ground. Tie these pins directly
to the local ground plane. Both pins must be tied.
VIN (Pin 8): Input Supply Pin. Bypass this pin with a
capacitor as close to the device as possible.
SW1 (Pin 10): Switch Pin for Switcher 1. This is the
collector of the internal NPN power switch. Minimize the
metal trace area connected to the pin to minimize EMI.
1945f
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