LTC1550/LTC1551
Low Noise, Switched
Capacitor Regulated
Voltage Inverters
FEATURES
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DESCRIPTION
The LTC
®
1550/LTC1551 are switched capacitor charge
pump voltage inverters which include internal linear post-
regulators to minimize output ripple. Output voltages are
fixed at – 4.1V, with ripple voltages typically below 1mV
P-P
.
The LTC1550 is also available in an adjustable output
voltage version. The LTC1550/LTC1551 are ideal for use
as bias voltage generators for GaAs transmitter FETs in
portable RF and cellular telephone applications.
The LTC1550/LTC1551 operate from single 4.5V to 6.5V
supplies and draw typical quiescent currents of 4.25mA
with a 5V supply. Each device includes a TTL compatible
Shutdown pin which drops supply current to 0.2µA typi-
cally. The LTC1550 Shutdown pin is active low (SHDN),
while the LTC1551 Shutdown pin is active high (SHDN).
Only four external components are required: an input bypass
capacitor, two 0.1µF charge pump capacitors and a filter
capacitor at the linear regulator output. The adjustable LTC1550
requires two additional resistors to set the output voltage. The
LTC1550/LTC1551 will supply up to 10mA output current
with a 5V supply, while maintaining guaranteed output
regulation of
±5%.
The fixed voltage LTC1550/LTC1551 are available in S0-8
plastic packages. The adjustable LTC1550 is available in a
16-pin SSOP.
Regulated Negative Voltage from a Single
Positive Supply
Low Output Ripple: Less Than 1mV
P-P
Typ
High Charge Pump Frequency: 900kHz Typ
Small Charge Pump Capacitors: 0.1µF
Requires Only Four External Capacitors
Fixed – 4.1V or Adjustable Output
Shutdown Mode Drops Supply Current to < 1µA
High Output Current: Up to 10mA, V
CC
= 5V
Output Regulation: 5%
Available in SO-8 and 16-Lead SSOP
APPLICATIONS
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GaAs FET Bias Generators
Negative Supply Generators
Battery-Powered Systems
Single Supply Applications
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
– 4.1V Generator with 1mV
P-P
Noise
V
CC
1
2
SHDN
V
CC
C1
+
V
OUT
SENSE
CP
OUT
LTC1551
3
4
GND
C1
–
6
5
FERRITE BEAD
C
OUT
10µF
V
OUT
= –4.1V
I
LOAD
= 5mA
C
L
0.1µF
1550/51 F01
V
OUT
Output Noise and Ripple
8
7
C
CP
0.1µF
+
4.7µF
C
IN
V
OUT
AC COUPLED
2mV/DIV
C1
0.1µF
U
U
+
U
10µs/DIV
1550/51 TA02
1
LTC1550/LTC1551
ABSOLUTE
MAXIMUM
RATINGS
Supply Voltage ......................................................... 7V
Output Voltage ................................ 0.3V to (V
CC
– 14V)
Total Voltage, V
CC
to CP
OUT .............................................
14V
Input Voltage (SHDN Pin) ........... – 0.3V to (V
CC
+ 0.3V)
Input Voltage (REG Pin)............................ – 0.3V to 12V
Output Short-Circuit Duration .............................. 30 sec
PACKAGE/ORDER INFORMATION
TOP VIEW
SHDN* 1
V
CC
2
C1
+
3
V
OUT
4
8
7
6
5
SENSE
CP
OUT
GND
C1
–
ORDER
PART NUMBER
LTC1550CS8-4.1
LTC1551CS8-4.1
S8 PACKAGE
8-LEAD PLASTIC SO
*SHDN FOR LTC1550, SHDN FOR LTC1551
T
JMAX
= 150°C,
θ
JA
= 150°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
V
CC
= 4.5V to 6.5V, C1 = C2 = 0.1µF, C
OUT
= 10µF, T
A
= 25°C unless otherwise specified. (Note 3)
SYMBOL
V
CC
PARAMETER
Supply Voltage
(LTC1550CGN/LTC1550IGN)
(LTC1550CS8-4.1/LTC1551CS8-4.1)
Reference Voltage
Supply Current
Internal Oscillator Frequency
REG Output Low Voltage
REG Sink Current
SHDN Input High Voltage
SHDN Input Low Voltage
SHDN Input Current
Turn-On Time
Output Regulation
(LTC1550CGN/LTC1550IGN)
Output Regulation
(LTC1550CGN/LTC1550IGN)
CONDITIONS
q
q
q
V
REF
I
S
f
OSC
V
OL
I
REG
V
IH
V
IL
I
IN
t
ON
V
OUT
V
CC
= 5V, V
SHDN
= V
CC
(LTC1550) or GND (LTC1551)
V
CC
= 5V, V
SHDN
= GND (LTC1550) or V
CC
(LTC1551)
I
REG
= 1mA, V
CC
= 5V
V
REG
= 0.8V, V
CC
= 5V
V
CC
= 5V
V
CC
= 5V
V
SHDN
= V
CC
I
OUT
= 10mA
2.7V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
2.8V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
3.5V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
2.7V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
3.1V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
3.75V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
V
OUT
2
U
U
W
W W
U
W
(Note 1)
Commercial Temperature Range ................. 0°C to 70°C
Extended Commercial Operating
Temperature Range (Note 3) .............. – 40°C to 85°C
Industrial Temperature Range ................ – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
TOP VIEW
NC 1
C1
+
2
16 V
CC
15 SHDN
14 REG
13 SENSE
12 ADJ
11 CP
OUT
10 NC
9
NC
ORDER
PART NUMBER
LTC1550CGN
LTC1550IGN
GN PART MARKING
1550
NC 3
V
OUT
4
C1
–
5
PGND 6
AGND 7
NC 8
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 150°C/ W
MIN
2.7
4.5
TYP
MAX
6.5
6.5
UNITS
V
V
V
mA
µA
kHz
V
mA
V
V
µA
ms
V
V
V
V
V
V
q
q
q
q
q
q
q
q
q
q
q
q
q
7
2
1.24
4.25
0.2
900
0.1
15
7
10
0.8
– 1.575
– 1.575
– 1.575
– 2.1
– 2.1
– 2.1
0.1
1
– 1.5
– 1.5
– 1.5
– 2.0
– 2.0
– 2.0
0.8
1
– 1.425
– 1.425
– 1.425
– 1.9
– 1.9
– 1.9
LTC1550/LTC1551
ELECTRICAL CHARACTERISTICS
V
CC
= 4.5V to 6.5V, C1 = C2 = 0.1µF, C
OUT
= 10µF, T
A
= 25°C unless otherwise specified. (Note 3)
SYMBOL
V
OUT
PARAMETER
Output Regulation
(LTC1550CGN/LTC1550IGN)
Output Regulation
(LTC1550CGN/LTC1550IGN)
Output Regulation
(LTC1550CGN/LTC1550IGN)
Output Regulation
(LTC1550CGN/LTC1550IGN)
Output Regulation
(LTC1550CGN/LTC1550IGN)
Output Regulation
(LTC1550CS8-4.1/LTC1551CS8-4.1)
Output Short-Circuit Current
Output Ripple Voltage
CONDITIONS
3.05V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
3.45V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
4.1V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
3.45V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
3.85V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
4.5V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
3.9V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
4.2V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
4.85V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
4.5V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
4.75V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
5.35V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
4.8V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
5.1V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
5.7V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
4.5V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
5mA
4.75V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
10mA
5.35V
≤
V
CC
≤
6.5V, 0
≤
I
OUT
≤
20mA
V
OUT
= 0V, V
CC
= 5V
V
OUT
= 0V, V
CC
= 6.5V
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
V
OUT
V
OUT
V
OUT
V
OUT
V
OUT
MIN
– 2.625
– 2.625
– 2.625
– 3.15
– 3.15
– 3.15
– 3.675
– 3.675
– 3.675
– 4.3
– 4.3
– 4.3
– 4.725
– 4.725
– 4.725
– 4.3
– 4.3
– 4.3
I
SC
V
RIPPLE
TYP
– 2.5
– 2.5
– 2.5
– 3.0
– 3.0
– 3.0
– 3.5
– 3.5
– 3.5
– 4.1
– 4.1
– 4.1
– 4.5
– 4.5
– 4.5
– 4.1
– 4.1
– 4.1
50
80
1
MAX
– 2.375
– 2.375
– 2.375
– 2.85
– 2.85
– 2.85
– 3.325
– 3.325
– 3.325
– 3.9
– 3.9
– 3.9
– 4.275
– 4.275
– 4.275
– 3.9
– 3.9
– 3.9
150
200
UNITS
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
mA
mA
mV
The
q
denotes specifications which apply over the specified
temperature range.
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified. All typicals are given at T
A
= 25°C.
Note 3:
C-grade device specifications are guaranteed over the 0°C to 70°C
temperature range. In addition, C-grade device specifications are assured
over the – 40°C to 85°C temperature range by design or correlation, but
are not production tested.
TYPICAL PERFORMANCE CHARACTERISTICS
Oscillator Frequency
vs Temperature
975
OSCILLATOR FREQUENCY (kHz)
925
875
825
775
725
V
OUT
= – 4.1V
V
CC
= 5V
SUPPLY CURRENT (mA)
5.0
4.5
4.0
3.5
3.0
–45 –25
OUTPUT VOLTAGE (V)
675
–45 –25
35
15
55
–5
TEMPERATURE (˚C)
U W
75
LTC1550/51 G01
Supply Current vs Temperature
6.0
V
OUT
= – 4.1V
5.5
Output Voltage vs Output Current
(LTC1550CS8-4.1/LTC1551CS8-4.1)
–3.0
T
A
= 25°C
–3.2
–3.4
V
CC
= 4.5V
–3.6
V
CC
= 5V
–3.8
–4.0
V
CC
= 6.5V
–4.2
V
CC
= 5V
95
55
–5
35
15
TEMPERATURE (°C)
75
95
0
5
25
10
15
20
OUTPUT CURRENT (mA)
30
LTC1550/51 G02
LTC1550/51 G03
3
LTC1550/LTC1551
TYPICAL PERFORMANCE CHARACTERISTICS
Maximum Output Current
vs Supply Voltage
50
MAXIMUM OUTPUT CURRENT (mA)
45
40
35
30
25
20
15
10
5
T
A
= 25°C
START-UP TIME (ms)
0
4.50 4.75 5.00 5.25 5.50 5.75 6.00 6.25 6.50
SUPPLY VOLTAGE (V)
LTC1550/51 • TPC04
Load Transient Response
(See Figure 2, V
CC
= 5V)
5mV/DIV
V
OUT
AC COUPLED
5mV/DIV
POSITIVE SUPPLY VOLTAGE (V)
10mA
I
OUT
0mA
1ms/DIV
V
CC
5.5V
5V
2ms/DIV
Output Spectrum
(*See Typical Application)
90
80
70
60
NOISE (µV/√Hz)
10
NOISE (dBµV)
50
40
30
20
10
0
–10
100k
1M
FREQUENCY (Hz)
10M
LT1550/51 • G09
NOISE (dBµV)
* On first page of data sheet.
4
U W
Start-Up Time vs Supply Voltage
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
4.50 4.75 5.00 5.25 5.50 5.75 6.00 6.25 6.50
SUPPLY VOLTAGE (V)
LTC1550/51 G05
Startup Time (LTC1550 Shown)
5V
SHDN
0V
0V
V
OUT
– 4.1V
0.2ms/DIV
T
A
= 25°C
V
OUT
= – 4.1V
R
L
= 390Ω
LTC1550/51 • G06
Line Transient Response
(See Figure 2, I
L
= 10mA)
6.0
5.6
5.2
4.8
4.4
4.0
3.6
3.2
2.8
2.4
2.0
Minimum Required V
CC
vs
V
OUT
and I
OUT
V
OUT
AC COUPLED
I
OUT
= 20mA
I
OUT
= 5mA
I
OUT
= 10mA
LTC1550/51 • G07
LTC1550/51 • G08
–5
–4
–2
–1
–3
OUTPUT VOLTAGE (V)
0
LTC1550/51 • G08.5
Spot Noise
(*See Typical Application)
90
80
70
1
Output Spectrum
(See Figure 2, C
OUT
= 10µF)
V
CC
= 5V
I
L
= 5mA
C
IN
= 4.7µF
C
OUT
= 10µF
C
L
= 0.1µF
60
50
40
30
20
10
0
0.1
0.01
1
10
FREQUENCY (kHz)
100
LTC1550/51 • G10
–10
100k
1M
FREQUENCY (Hz)
10M
LT1550/51 • G11
LTC1550/LTC1551
TYPICAL PERFORMANCE CHARACTERISTICS
Spot Noise
(See Figure 2, C
OUT
= 10µF)
10
V
CC
= 5V
I
L
= 5mA
C
IN
= 4.7µF
C
OUT
= 10µF
C
L
= 0.1µF
NOISE (µV/√Hz)
50
40
30
20
10
0
0.1
NOISE (µV/√Hz)
NOISE (dBµV)
1
0.01
1
10
FREQUENCY (kHz)
100
LTC1550/51 • G12
PIN FUNCTIONS
SHDN:
Shutdown (TTL Compatible). This pin is active low
(SHDN) for the LTC1550 and active high (SHDN) for the
LTC1551. When this pin is at V
CC
(GND for LTC1551), the
LTC1550 operates normally. When SHDN is pulled low
(high for LTC1551), the LTC1550 enters shutdown mode.
In shutdown, the charge pump stops, the output collapses
to 0V, and the quiescent current drops typically to 0.2µA.
V
CC
:
Power Supply. V
CC
requires an input voltage between
4.5V and 6.5V for the fixed voltage LTC1550CS8-4.1/
LTC1551CS8-4.1. The adjustable voltage LTC1550CGN/
LTC1550IGN operates with a VCC range of 2.7V to 6.5V.
Output voltage and output load current conditions depend
on the VCC supply voltage. Consult the Electrical Charac-
teristics table and Typical Performance Characteristics for
guaranteed test points. The difference between the input
voltage and output should never be set to exceed 14V or
damage to the chip may occur. V
CC
must be bypassed to
PGND (GND for 8-pin packages) with at least a 0.1µF
capacitor placed in close proximity to the chip. A 4.7µF or
larger bypass capacitor is recommended to minimize
noise and ripple at the output.
C1
+
:
C1 Positive Input. Connect a 0.1µF capacitor between
C1
+
and C1
–
.
V
OUT
:
Negative Voltage Output. This pin must be bypassed
to ground with a 4.7µF or larger capacitor to ensure
regulator loop stability. At least 10µF is recommended to
provide specified output ripple. An additional 0.1µF low
ESR capacitor is recommended to minimize high fre-
quency spikes at the output.
C1
–
:
C1 Negative Input. Connect a 0.1µF capacitor from
C1
+
to C1
–
.
GND:
Ground. Connect to a low impedance ground. A
ground plane will help minimize regulation errors.
CP
OUT
:
Negative Charge Pump Output. This pin requires a
0.1µF storage capacitor to ground.
SENSE:
Connect to V
OUT
. The LTC1550/LTC1551 internal
regulator uses this pin to sense the output voltage. For
optimum regulation, SENSE should be connected close to
the output load.
SSOP PACKAGE ONLY
PGND:
Power Ground. Connect to a low impedance ground.
PGND should be connected to the same potential as
AGND.
AGND:
Analog Ground. Connect to a low impedance
ground. AGND should be connected to a ground plane to
minimize regulation errors.
U W
Output Spectrum
(See Figure 2, C
OUT
= 22µF)
90
80
70
60
V
CC
= 5V
I
L
= 5mA
C
IN
4.7µF
C
OUT
= 22µF
C
L
= 0.1µF
10
Spot Noise
(See Figure 2, C
OUT
= 22µF)
V
CC
= 5V
I
L
= 5mA
C
IN
= 4.7µF
C
OUT
= 22µF
C
L
= 0.1µF
1
0.1
–10
100k
1M
FREQUENCY (Hz)
10M
LT1550/51 • G13
0.01
1
10
FREQUENCY (kHz)
100
LTC1550/51 • G14
U
U
U
5
嵌入式系统
