LTC1550LCS8#PBF [Linear]
LTC1550L - Low Noise, Switched Capacitor Regulated Voltage Inverters; Package: SO; Pins: 8; Temperature Range: 0°C to 70°C;
| 型号： | LTC1550LCS8#PBF |
| 厂家： | 
Linear |
| 描述： | LTC1550L - Low Noise, Switched Capacitor Regulated Voltage Inverters; Package: SO; Pins: 8; Temperature Range: 0°C to 70°C 光电二极管 |
| 文件： | 总12页 (文件大小：239K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC1550L/LTC1551L
Low Noise, Switched
Capacitor Regulated
Voltage Inverters
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DESCRIPTIO
FEATURES
The LTC®1550L/LTC1551L are switched capacitor charge
pump voltage inverters which include internal linear post-
regulators to minimize output ripple. The LTC1550L fixed
output voltage versions include–4.1V, –2.5Vand–2Vwith
ripple voltages typically below 1mVP-P. The LTC1550L is
also available in an adjustable output voltage version. The
LTC1550L/LTC1551L are ideal for use as bias voltage
generators for GaAs transmitter FETs in portable RF and
cellular telephone applications.
■
Regulated Negative Voltage from a Single
Positive Supply
■
Low Output Ripple: Less Than 1mVP-P Typ
■
High Charge Pump Frequency: 900kHz
■
Small Charge Pump Capacitors: 0.1µF
■
Requires Only Four External Capacitors
■
Fixed –4.1V, –2.5V, –2V or Adjustable Output
■
Shutdown Mode Drops Supply Current to <1µA
■
High Output Current: Up to 20mA (Depending on
VCC to VOUT Range)
The LTC1550L/LTC1551L operate from single 2.7V to
5.5V supplies and draw typical quiescent currents of
3.5mA with a 5V supply. Each device includes a TTL
compatible Shutdown pin which drops supply current to
0.2µA typically. The LTC1550L Shutdown pin is active low
(SHDN), while the LTC1551L Shutdown pin is active high
(SHDN). Only four external components are required: an
inputbypasscapacitor, two 0.1µF charge pump capacitors
and a filter capacitor at the linear regulator output. The
adjustable LTC1550L/LTC1551L require two additional re-
sistors to set the output voltage. The LTC1550L/LTC1551L
will supply up to 20mA (depending on VCC to VOUT range),
while maintaining guaranteed output regulation of ±2.5%.
■
Output Regulation: 2.5% Over Line, Load and
Temperature
■
Available in 8-Lead MSOP, 8-Lead Narrow SO and
16-Lead Narrow SSOP
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APPLICATIO S
■
GaAs FET Bias Generators
■
Negative Supply Generators
■
Battery-Powered Systems
Single Supply Applications
■
Both fixed voltage and adjustable LTC1550L/LTC1551L
are available in 8-lead MSOP and SO plastic packages: the
adjustable LTC1550L is also available in a 16-pin SSOP
with the REG pin.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
VOUT Output Noise and Ripple
R1
10k
1
2
8
7
3.6V
POWER VALID
SHDN
REG
V
CP
OUT
CC
+
2.2µF
IN
C
CP
0.1µF
VOUT
AC COUPLED
2mV/DIV
LTC1550L-2
C
3
4
6
+
C1
GND
5
–
V
C1
OUT
V
LOAD
= –2V
= 5mA
OUT
I
C
C
OUT
L
+
10µF
0.1µF
C1
0.1µF
1550L/51L TA01
5µs/DIV
1550L/51L TA01a
Figure 1. –2V Generator with 1mVP-P Noise
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LTC1550L/LTC1551L
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage ...................................................... 5.5V
Output Voltage............................. 0.3V to (VCC – 10.5V)
Total Voltage, VCC to CPOUT .......................................... 10.8V
Input Voltage (SHDN Pin) ........... –0.3V to (VCC + 0.3V)
Input Voltage (REG Pin) ............................. – 0.3V to 6V
Output Short-Circuit Duration.............................. 30 sec
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
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PACKAGE/ORDER INFORMATION
TOP VIEW
TOP VIEW
TOP VIEW
SHDN*
1
2
3
4
8 REG (ADJ*)
7 CP
SHDN*
1
2
3
4
8
7
6
5
NC
+
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
REG (ADJ*)
V
CC
V
C1
CC
OUT
+
6 GND
C1
SHDN
REG
NC
V
CP
OUT
CC
+
–
5 C1
V
OUT
NC
C1
GND
MS8 PACKAGE
8-LEAD PLASTIC MSOP
–
V
OUT
V
C1
OUT
–
C1
ADJ
*SHDN FOR LTC1550L, SHDN FOR LTC1551L
*FOR ADJUSTABLE VERSION
S8 PACKAGE
8-LEAD PLASTIC SO
PGND
AGND
NC
CP
NC
NC
OUT
TJMAX = 150°C, θJA = 200°C/W
*SHDN FOR LTC1550L, SHDN FOR LTC1551L
*FOR ADJUSTABLE VERSION
ORDER PART NUMBER
TJMAX = 150°C, θJA = 135°C/W
GN PACKAGE
16-LEAD PLASTIC SSOP
LTC1550LCMS8
LTC1551LCMS8
LTC1551LCMS8-4.1
TJMAX = 150°C, θJA = 150°C/W
ORDER PART NUMBER
LTC1550LCMS8-2
LTC1550LCMS8-2.5
LTC1550LCMS8-4.1
LTC1550LCS8
ORDER PART NUMBER
LTC1550LCS8-2
LTC1550LCS8-2.5
LTC1550LCS8-4.1
LTC1551LCS8
LTC1550LCGN
LTC1550LIGN
MS8 PART MARKING
LTEG
LTGR
LTFV
LTEH
LTFQ
LTFT
GN PART MARKING
LTC1551LCS8-4.1
1550L
1550LI
Consult factory for Military grade parts and additional voltage options.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VCC = 2.7V to 5.25V, C1 = CCP = 0.1µF, COUT = 10µF, TA = 25°C unless otherwise specified. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Supply Voltage
(Adjustable, Fixed –2V)
(Fixed –2.5V)
CC
●
●
●
2.7
3.05
4.5
5.25
5.25
5.25
V
V
V
(Fixed –4.1V)
V
Reference Voltage
Reference Voltage
Line Regulation
OUT)
V
= 5V, ADJ = GND, V = –V
OUT
1.225
2.5
V
mV/V
REF
CC
REF
∆V
CC
I
= 0mA, 2.7V ≤ V ≤ 5.25V
REF
OUT
CC
∆(V – V
I
Supply Current
V
V
= 5V, V
= 5V, V
= V (LTC1550L) or GND (LTC1551L)
●
●
3.65
0.2
7
10
mA
µA
S
CC
CC
SHDN
SHDN
CC
= GND (LTC1550L) or V (LTC1551L)
CC
2
LTC1550L/LTC1551L
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VCC = 2.7V to 5.25V, C1 = CCP = 0.1µF, COUT = 10µF, TA = 25°C unless otherwise specified. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
= 1mA, V = 5V
MIN
TYP
MAX
UNITS
f
Internal Oscillator Frequency
REG Output Low Voltage
REG Sink Current
SHDN Input High Voltage
SHDN Input Low Voltage
SHDN Input Current
900
0.1
10
kHz
V
mA
V
V
µA
µA
OSC
V
I
●
●
●
●
0.8
OL
REG
CC
I
V
= 0.8V, V = 5V
4
2
REG
REG
CC
V
V
V
V
= 5V
= 5V
IH
IL
CC
CC
0.8
1
20
I
V
V
= V (All LTC1550L Versions)
●
●
0.1
5
IN
SHDN
SHDN
CC
= V (All LTC1551L Versions)
CC
t
Turn-On Time
V
= 5V, I
= 10mA, –1.5V ≤ V ≤ 4.1V
OUT
●
●
●
●
●
1
1
1
1
1
5
5
5
5
5
ms
ms
ms
ms
ms
ON
CC
OUT
(LTC1550L/LTC1551L)
= 5V, I = 5mA, V = –4.5V
OUT
V
CC
OUT
(LTC1550L/LTC1551L)
V
(LTC1550L-2)
V
(LTC1550L-2.5)
V
= 5V, I = 10mA, V
= –2V
CC
OUT
OUT
OUT
OUT
= 5V, I = 10mA, V
OUT
= –2.5V
= –4.1V
CC
= 5V, I = 10mA, V
CC
OUT
(LTC1550L-4.1/LTC1551L-4.1)
V
V
V
V
V
V
V
Output Regulation
(LTC1550L/LTC1551L)
2.7V ≤ V ≤ 5.25V, 0 ≤ I
≤ 5mA
≤ 10mA
≤ 20mA
≤ 5mA
≤ 10mA
●
●
●
–1.537
–1.537
–1.537
–2.05
–2.05
–2.05
–2.562
–2.562
–2.562
–3.075
–3.075
–3.075
–3.587
–3.587
–3.587
–4.203
–4.203
–1.5
–1.5
–1.5
–2.0
–2.0
–2.0
–2.5
–2.5
–2.5
–3.0
–3.0
–3.0
–3.5
–3.5
–3.5
–4.1
–4.1
–1.463
–1.463
–1.463
–1.95
–1.95
–1.95
–2.438
–2.438
–2.438
–2.925
–2.925
–2.925
–3.413
–3.413
–3.413
–3.998
–3.998
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
OUT
OUT
OUT
OUT
OUT
OUT
OUT
CC
OUT
OUT
OUT
2.8V ≤ V ≤ 5.25V, 0 ≤ I
CC
3.5V ≤ V ≤ 5.25V, 0 ≤ I
CC
Output Regulation
(LTC1550L/LTC1550L-2/
LTC1551L)
Output Regulation
(LTC1550L/LTC1550L-2.5/
LTC1551L)
2.7V ≤ V ≤ 5.25V, 0 ≤ I
●
●
●
CC
OUT
3.1V ≤ V ≤ 5.25V, 0 ≤ I
CC
OUT
3.75V ≤ V ≤ 5.25V, 0 ≤ I
≤ 20mA
CC
OUT
3.05V ≤ V ≤ 5.25V, 0 ≤ I
≤ 5mA
●
●
●
CC
OUT
3.45V ≤ V ≤ 5.25V, 0 ≤ I
≤ 10mA
CC
OUT
4.1V ≤ V ≤ 5.25V, 0 ≤ I
≤ 20mA
CC
OUT
Output Regulation
(LTC1550L/LTC1551L)
3.45V ≤ V ≤ 5.25V, 0 ≤ I
≤ 5mA
●
●
●
CC
OUT
3.85V ≤ V ≤ 5.25V, 0 ≤ I
≤ 10mA
CC
OUT
4.5V ≤ V ≤ 5.25V, 0 ≤ I
≤ 20mA
≤ 5mA
≤ 10mA
CC
OUT
Output Regulation
(LTC1550L/LTC1551L)
3.9V ≤ V ≤ 5.25V, 0 ≤ I
●
●
●
CC
OUT
4.2V ≤ V ≤ 5.25V, 0 ≤ I
CC
OUT
4.85V ≤ V ≤ 5.25V, 0 ≤ I
≤ 20mA
CC
OUT
Output Regulation
(LTC1550L/LTC1550L-4.1)
(LTC1551L/LTC1551L-4.1)
Output Regulation
4.5V ≤ V ≤ 5.25V, 0 ≤ I
≤ 5mA
●
●
CC
OUT
4.75V ≤ V ≤ 5.25V, 0 ≤ I
≤ 10mA
CC
OUT
4.8V ≤ V ≤ 5.25V, 0 ≤ I
≤ 5mA
≤ 10mA
●
●
–4.613
–4.613
–4.5
–4.5
–4.388
–4.388
V
V
CC
OUT
OUT
(LTC1550L/LTC1551L))
5.1V ≤ V ≤ 5.25V, 0 ≤ I
CC
I
V
Output Short-Circuit Current
Output Ripple Voltage
V
= 0V, V = 5.25V
●
80
1
200
mA
mV
SC
OUT
CC
RIPPLE
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
Note 3: The LTC1550LC/LTC1551LC are guaranteed to meet specified
performance from 0°C to 70°C and are designed, characterized and
expected to meet these extended temperature limits, but are not tested at
–40°C and 85°C. The LTC1550LI is guaranteed to meet the extended
temperature limits.
specified. All typicals are given at T = 25°C.
A
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LTC1550L/LTC1551L
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TYPICAL PERFORMANCE CHARACTERISTICS
Oscillator Frequency vs
Temperature
Minimum Required VCC
vs VOUT and IOUT
Supply Current vs Temperature
5.0
4.5
4.0
3.5
3.0
2.5
975
925
875
825
6.0
5.6
5.2
4.8
4.4
4.0
3.6
3.2
2.8
2.4
2.0
V
V
= 5V
OUT
V
V
= 5V
OUT
CC
CC
= –4.1V
= –4.1V
I
= 20mA
OUT
775
725
675
I
= 10mA
–1
OUT
I
= 5mA
–3
OUT
–55 –35 –15
5
25 45 65 85 105 125
–55 –35 –15
5
25 45 65 85 105 125
–5
–4
–2
0
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
TEMPERATURE (˚C)
1550L/51L G03
1550L/51L G02
1550L/51L G01
Maximum Output Current
vs Supply Voltage
Start-Up Time vs Supply Voltage
Reference Voltage vs VCC + |VOUT|
1.24
1.238
1.236
1.234
1.232
1.230
1.228
1.226
1.224
1.222
1.220
1.218
80
70
60
50
40
30
20
10
0
2.5
2.0
1.5
1.0
0.5
0
T
= 25°C
T
= 25°C
T = 25°C
A
A
A
V
= –4.1V
OUT
L
R
= 820Ω
V
= –2V
OUT
V
= –2V
V
= –2.5V
R = 390Ω
L
OUT
OUT
V
OUT
= –4.1V
2.25 2.75 3.25 3.75 4.25 4.75 5.25
2.25 2.75 3.25 3.75 4.25 4.75 5.25
SUPPLY VOLTAGE (V)
4
4.5
5
5.5
6
V
6.5
7 7.5 8 8.5 9 9.5 10
SUPPLY VOLTAGE (V)
+ |V | (V)
CC
OUT
1550L/51L G04
1550L/51L G05
1550L/51L G06
Load Transient Response
(See Figure 3, VCC = 5V)
Line Transient Response
(See Figure 3, IL = 10mA)
Startup Time (LTC1550L Shown)
5V
SHDN
0V
VOUT
5mV/DIV
AC
VOUT
5mV/DIV
0V
AC
COUPLED
COUPLED
VOUT
–4.1V
5V
10mA
IOUT
5.25V
VCC
4.75V
POWER VALID
0V
0mA
0.2ms/DIV
1550/51 G07
1ms/DIV
1550/51 G08
2ms/DIV
1550/51 G09
4
LTC1550L/LTC1551L
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TYPICAL PERFORMANCE CHARACTERISTICS
Output Spectrum (*See Figure 1)
Spot Noise (*See Figure 1)
Output Spectrum (See Figure 3)
90
80
70
60
50
40
30
20
10
0
10
90
V
L
C
C
C
= 5V
CC
80
70
60
50
40
30
20
10
0
I
= 5mA
= 2.2µF
IN
= 4.7µF
OUT
= 0.1µF
L
1
0.1
–10
–10
0.01
100k
1M
FREQUENCY (Hz)
10M
100k
1M
10M
1
10
100
FREQUENCY (Hz)
FREQUENCY (kHz)
1550L/51L G12
1550L/51L G10
1550 /51L G11
Output Spectrum (See Figure 3)
Spot Noise (See Figure 3)
Spot Noise (See Figure 3)
10
10
90
80
70
60
50
40
30
20
10
0
V
L
C
C
C
= 5V
V
I
C
C
C
= 5V
CC
CC
L
IN
I
= 5mA
= 5mA
= 2.2µF
2.2µF
IN
= 10µF
= 10µF
OUT
OUT
= 0.1µF
= 0.1µF
L
L
1
1
0.1
V
L
C
C
C
= 5V
CC
0.1
I
= 5mA
= 2.2µF
OUT
= 0.1µF
IN
= 4.7µF
L
0.01
–10
0.01
1
10
FREQUENCY (kHz)
100
100k
1M
10M
1
10
FREQUENCY (kHz)
100
FREQUENCY (Hz)
1550L/51L G14
1550L/51L G13
1550L/51L G15
* On first page of data sheet.
5
LTC1550L/LTC1551L
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PIN FUNCTIONS
SHDN: Shutdown (TTL Compatible). This pin is active low
(SHDN) for the LTC1550L and active high (SHDN) for the
LTC1551L. When this pin is at VCC (GND for LTC1551L),
the LTC1550L operates normally. When SHDN is pulled
low (SHDN pulled high for LTC1551L), the LTC1550L
enters shutdown mode. In shutdown, the charge pump
stops, the output collapses to 0V, and the quiescent
current drops typically to 0.2µA. The SHDN pin for the
LTC1550L is a high impedance input and has no internal
pull-up. The user must supply a resistor or current source
pull-up to default the LTC1550L into normal operation.
The SHDN pin for the LTC1551L has an internal 5µA
typical pull-down that defaults the LTC1551L into normal
operation.
should connect directly to the VCC and CPOUT bypass
capacitors, as well as to the GND of the LTC1550L/
LTC1551L.LTCrecommendsaseparatetracefortheVOUT
capacitor ground connection to minimize noise.
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.
CPOUT: Negative Charge Pump Output. This pin requires a
0.1µF storage capacitor to ground. In order to achieve
ripple on the output voltage of less than 1mV, the ground
connection for the CPOUT capacitor must tie directly to the
bottom of the VCC bypass capacitor and at the GND pin of
the LTC1550L/LTC1551L. This minimizes the AC current
path for the charge pump.
VCC:PowerSupply. VCC requiresaninputvoltagebetween
2.7V and 5.25V. Certain combinations of output voltage
and output load current may place additional restrictions
on the required input voltage. Consult the Electrical Char-
acteristics table and Typical Performance Characteristics
for guaranteed test points. The difference between the
input voltage and output should not exceed 10.5V or
damage to the chip may occur. VCC must be bypassed
directly to PGND (GND for 8-pin packages) with at least a
0.1µFcapacitorplacedincloseproximitytothechip.A1µF
or larger low ESR bypass capacitor is recommended to
minimize noise and ripple at the output. A surface mount
ceramic capacitor is recommended.
REG: This is an open-drain output that pulls low when the
outputvoltageiswithin5%ofthesetvalue.Itwillsink4mA
to ground with a 5V supply. The external circuitry must
provide a pull-up or REG will not swing high. The voltage
at REG may exceed VCC and can be pulled up to 6V above
ground without damage. For the LTC1550L adjustable
voltageversion,theREGpinisonlyavailableinthe16-lead
GN package.
ADJ (for adjustable versions): This is the feedback point
for the external resistor divider string. Connect a divider
string from GND to VOUT with the divided tap connected to
ADJ. Note that the resistor string needs to be connected
“upside-down”fromanegativeregulator.SeetheApplica-
tions Information section for hook-up details.
C1+:C1PositiveInput.Connecta0.1µFcapacitorbetween
C1+ and C1–.
VOUT:NegativeVoltageOutput.Thispinmustbebypassed
with a 4.7µF or larger capacitor to ensure regulator loop
stability. LTC recommends at least 10µF to achieve the
specified output ripple. The output capacitor should be a
moderate ESR capacitor, and not a very low ESR capaci-
tor, as the zero in the feedback loop (formed by the ESR
and the output capacitor) provides phase lead to the linear
regulator feedback loop. Using very low ESR output ca-
pacitors will result in the output oscillating. A low ESR
0.1µF capacitor is recommended in parallel with the main
output capacitor to minimize high frequency spikes at the
output. The ground connection for the output capacitor
GN PACKAGE ONLY
PGND:PowerGround.Connecttoalowimpedanceground.
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.
NC: No Internal Connection.
6
LTC1550L/LTC1551L
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BLOCK DIAGRAM
+
C
CP
C
OUT
V
CP
CC
OUT
S1
LINEAR
REGULATOR
V
OUT
S4
+
C1
CLK
900kHz
C1
–
S2
C1
+
–
**
**
S3
ADJ
REG
CHARGE
PUMP
*SHDN
+
–
58mV
COMP2
1.225V
1.167V
1550L/51L BD
*SHDN FOR LTC1550L, SHDN FOR LTC1551L
** FIXED OUTPUT VERSIONS ONLY
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APPLICATIONS INFORMATION
generators for GaAs transmitter FETs in portable RF and
cellulartelephoneapplications. TheLTC1550Lfeaturesan
active-low Shutdown pin (SHDN) that drops quiescent
current to below 1µA. The LTC1551L is identical to the
LTC1550L, except that the Shutdown pin is active-high
(SHDN). All members of the LTC1550L/LTC1551L family
feature a 900kHz charge pump frequency. The LTC1550L/
LTC1551L come standard with fixed –4.1V, –2.5V, –2V
and adjustable outputvoltages. The LTC1550L/LTC1551L
can be configured for other fixed output voltages; contact
Linear Technology for more information.
OVERVIEW
TheLTC1550L/LTC1551Lareswitchedcapacitor,inverting
charge pumps with internal linear post-regulators. The
LTC1550L/LTC1551Lprovidearegulated,lowrippleoutput
at up to 20mA load current with the appropriate input
voltage as output load current depends on the input/
outputvoltagecombination. Consultthegraphprovidedin
the Typical Performance Characteristics section and the
Electrical Characteristics table for guaranteed test points.
The LTC1550L/LTC1551L are ideal for use as bias voltage
7
LTC1550L/LTC1551L
U
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APPLICATIONS INFORMATION
The LTC1550L/LTC1551L consist of two major blocks
(see Block Diagram): an inverting charge pump and a
negative linear regulator. The charge pump uses two
external capacitors, C1 and CCP to generate a negative
voltage at CPOUT. It operates by charging and discharging
C1 on alternate phases of the internal 900kHz clock. C1 is
initiallychargedtoVCC throughswitchesS1andS3. When
the internal clock changes phase, S1 and S3 open and S2
and S4 close, shorting the positive side of C1 to ground.
This forces the negative side of C1 below ground, and
charge is transferred to CCP through S4. As this cycle
repeats,themagnitudeofthenegativevoltageapproaches
VCC.The900kHzinternalclockfrequencyhelpskeepnoise
out of the 400kHz to 600kHz IF bands commonly used by
portable radio frequency systems and reduces the size of
the external capacitors required. Most applications can
use standard 0.1µF ceramic capacitors for C1 and CCP.
Increasing C1 and CCP beyond 0.1µF has little effect on the
output ripple or the output current capacity of the
LTC1550L/LTC1551L.
PGND, AGND
R1
R2
LTC1550L ADJ
R1 + R2
R2
V
V
= –1.225V
OUT
OUT
(
)
1550L/51L • F02
Figure 2. External Resistor Connections
referenced to ground. The output resistor divider must be
set to provide 1.225V at the ADJ pin with respect to VOUT
.
For example, a –3V output would require a 17.4k resistor
from GND to ADJ, and a 12.1k resistor to VOUT
.
CAPACITOR SELECTION
The LTC1550L/LTC1551L requires four external capaci-
tors: an input bypass capacitor, two 0.1µF charge pump
capacitors and an output filter capacitor. The overall
behavior of the LTC1550L/LTC1551L is strongly affected
by how the capacitors are used, and by how the capacitors
are laid out on the printed circuit board (PCB). In particu-
lar, theoutputcapacitor’svalueandESRhaveasignificant
effect on the output ripple and noise performance. In
addition, the ground connections for the VCC bypass
capacitor, the CPOUT capacitor and the VOUT bypass ca-
pacitor must employ star-ground techniques at the GND
pin of the LTC1550L/LTC1551L. Proper capacitor selec-
tion is critical for optimum performance of the LTC1550L/
LTC1551L.
The negative voltage at CPOUT supplies the input to the
negative regulator block. This block consists of an
N-channel MOSFET pass device and a feedback amplifier
that monitors the output voltage and compares it to the
internal reference. The regulated output appears at the
VOUT pin. The regulation loop is optimized for fast tran-
sient response, enabling it to remove most of the switch-
ing artifacts present at the CPOUT pin. Output ripple is
typically below 1mVP-P with output loads between 0mA
and 10mA. The output voltage is set by a pair of internal
divider resistors for the fixed voltage versions. The N-
channel pass device minimizes dropout, allowing the
output to remain in regulation with supply voltages as low
as 2.7V for an output voltage of –2V. An output capacitor
of at least 4.7µF from VOUT to ground is required to keep
the regulator loop stable; for optimum stability and mini-
mum output ripple, at least 10µF is recommended.
Output Ripple vs Output Capacitor
Figure 4 shows the effect of using different output capaci-
tor values on the LTC1550L/LTC1551L output ripple.
These curves are taken using the LTC1551L circuit in
Figure 3, with CIN = 2.2µF and ILOAD = 5mA. The upper
curve shows the performance with a standard tantalum
capacitor alone and the lower curve shows that of the
tantalum capacitor in parallel with a 0.1µF ceramic capaci-
tor. As a general rule, larger output capacitors provide
lower output ripple. To keep output voltage ripple below
1mVP–P, 10µF, or greater, in parallel with a 0.1µF ceramic
capacitor is required. To guarantee loop stability under all
conditions, a minimum of 4.7µF is required at the output.
Adjustable Hook-Up
For the adjustable LTC1550L/LTC1551L, the output volt-
age is set with a resistor divider from GND to VOUT
(Figure 2). Note that the internal reference and the internal
feedback amplifier are set up as a positive-output regula-
tor referenced to the VOUT pin, not as a negative regulator
8
LTC1550L/LTC1551L
U
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APPLICATIONS INFORMATION
A series RC or LC filter can reduce high frequency output
noise even further. Due to the high 900kHz switching
frequency, not much R or L is required; a ferrite bead or a
relatively long PC board trace in series with 0.1µF ceramic
capacitor will usually keep the output ripple well below
1mVP-P. Figure 1 shows an example of an ultralow noise
–2V generator. The corresponding spectrum and spot
noise plots for this circuit are shown in the Typical Perfor-
mance Characteristics section.
Figure 4 shows a marked decrease in peak-to-peak output
ripple when a 0.1µF ceramic capacitor is added in parallel
with the tantalum output capacitor. The additional ripple
with the tantalum output capacitor alone is mostly very
high order harmonics of the 900kHz clock, which appear
as sharp "spikes" at the output. The energy in these spikes
is very small and they do not contribute to the RMS output
voltage, but their peak-to-peak amplitude can be several
millivolts under some conditions. A 0.1µF ceramic capaci-
tor has significantly lower impedance at the spike fre-
quency than a large tantalum capacitor, and eliminates
most of these left-over switching spikes that the tantalum
capacitorleavesbehind.Figure5and6showscopephotos
of the output of Figure 4 with and without the additional
ceramic capacitor at the output.
8
V
T
= 5V
CC
A
IN
= 25°C
7
6
5
4
3
2
1
0
C
= 2.2µF
R1
10k
1
2
8
7
V
CC
SHDN
REG
CP
WITHOUT 0.1µF
V
CC
OUT
+
C
C
IN
CP
LTC1551L
2.2µF
0.1µF
3
4
6
+
C1
GND
5
WITH 0.1µF
–
V
C1
OUT
V
OUT
–4.1V
1
10
100
C
C
OUT
L
+
10µF
OUTPUT CAPACITANCE (µF)
0.1µF
C1
1550L/51L F04
0.1µF
1550L/51L F03
Figure 3. Output Ripple Test Circuit
Figure 4. Output Ripple vs Output Capacitance
VOUT
AC COUPLE
2mV/DIV
VOUT
AC COUPLE
5mV/DIV
5µs/DIV
1550L/51L F05
10µs/DIV
1550L/51L F06
Figure 5. Output Ripple with 10µF Tantalum Capacitor
Figure 6. Output Ripple with 10µF Tantalum
Capacitor Paralleled with 0.1µF Ceramic Capacitor
9
LTC1550L/LTC1551L
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APPLICATIONS INFORMATION
Output Ripple vs Input Bypass Capacitor
C1. Surface mount tantalum or ceramic capacitors with
lowESRgenerallyprovideadequateperformance.Figure 7
showstheLTC1550L/LTC1551Lpeak-to-peakoutputripple
vsCIN, takenusingthetestcircuitinFigure3withILOAD set
at 5mA. COUT is a 10µF in parallel with a 0.1µF ceramic
capacitor.
The input bypass capacitor (CIN) can also have a fairly
significant impact on the output ripple. CIN provides most
of the LTC1550L/LTC1551L’s supply current while it is
charging the flying capacitor (C1). Inadequate input
bypassing can cause the VCC supply to dip when the
chargepumpswitches,causingtheoutputlinearregulator
to momentarily stop regulating. CIN should be mounted as
close to the LTC1550L/LTC1551L VCC and GND pins as
possible and its value should be significantly larger than
A 2.2µF surface mount ceramic capacitor at VCC generally
provides adequate output ripple performance for most
applications.
8
V
A
C
= 5V
CC
7
6
5
4
3
2
1
0
T
= 25°C
= 10µF
OUT
0.1
1
10
100
INPUT CAPACITANCE (µF)
1550L/51L F08
Figure 7. Output Ripple vs Input Bypass Capacitance
U
TYPICAL APPLICATION
–4.1V Output GaAs FET Bias Generator
1
2
8
7
SHDN
REG
CP
4.5V ≤ V ≤ 5.25V
CC
V
CC
OUT
+
C
CP
0.1µF
C
IN
2.2µF
LTC1550L-4.1
+
3
4
6
C1
GND
5
–
V
OUT
C1
–4.1V BIAS
C
C
L
0.1µF
OUT
GaAs
TRANSMITTER
+
10µF
C1
0.1µF
1550L/51L TA02
10
LTC1550L/LTC1551L
U
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
GN Package
16-Lead Plastic SSOP (Narrow 0.150)
(LTC DWG # 05-08-1641)
0.189 – 0.196*
(4.801 – 4.978)
0.009
(0.229)
REF
16 15 14 13 12 11 10 9
0.229 – 0.244
(5.817 – 6.198)
0.150 – 0.157**
(3.810 – 3.988)
1
2
3
4
5
6
7
8
0.015 ± 0.004
(0.38 ± 0.10)
× 45°
0.053 – 0.068
(1.351 – 1.727)
0.004 – 0.0098
(0.102 – 0.249)
0.007 – 0.0098
(0.178 – 0.249)
0° – 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.0250
(0.635)
BSC
0.008 – 0.012
(0.203 – 0.305)
* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
GN16 (SSOP) 1098
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8
7
6
5
0.040 ± 0.006
(1.02 ± 0.15)
0.034 ± 0.004
(0.86 ± 0.102)
0.007
(0.18)
0° – 6° TYP
0.118 ± 0.004**
(3.00 ± 0.102)
SEATING
PLANE
0.193 ± 0.006
(4.90 ± 0.15)
0.012
(0.30)
REF
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
0.0256
(0.65)
BSC
MSOP (MS8) 1098
1
2
3
4
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
LTC1550L/LTC1551L
U
TYPICAL APPLICATION
1mVP-P Ripple, –2V Output GaAs FET Bias Generator
10k
1
2
8
7
REG
SHDN
REG
2.7V ≤ V ≤ 5.25V
CC
V
CC
CP
OUT
+
C
CP
0.1µF
C
IN
2.2µF
LTC1550L-2
3
4
6
+
C1
GND
5
–
V
C1
OUT
–2V
C
C
L
0.1µF
OUT
GaAs
TRANSMITTER
+
10µF
C1
0.1µF
1550L/51L TA03
U
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
0.010 – 0.020
(0.254 – 0.508)
7
5
8
6
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
1
3
4
2
SO8 1298
RELATED PARTS
PART NUMBER
LT®1054
DESCRIPTION
COMMENTS
Switched-Capacitor Voltage Converter with Regulator
Switched-Capacitor Regulated Voltage Inverter
Switched-Capacitor Regulated Voltage Inverter
Clock-Synchronized Switched-Capacitor Voltage Inverter
100mA Switched-Capacitor Converter
Selectable Fixed Output Voltages
LTC1261
LTC1261L
LTC1429
Adjustable and Fixed Output Voltages, Up to 20mA I , MSOP
OUT
Synchronizable Up to 2MHz System Clock
LTC1514/LTC1515 Step-Up/Step-Down Switched-Capacitor DC/DC Converters
V
2V to 10V, Adjustable or Fixed V , I
to 50mA
IN
OUT OUT
LTC1516
LTC1522
Micropower Regulated 5V Charge Pump DC/DC Converter
Micropower Regulated 5V Charge Pump DC/DC Converter
I
I
= 20mA (V ≥ 2V), I
= 50mA (V ≥ 3V)
OUT
OUT
IN
OUT IN
= 10mA (V ≥ 2.7V), I
= 20mA (V ≥ 3V)
IN
IN
OUT
LTC1550/LTC1551 Low Noise, Switched-Capacitor Regulated Voltage Inverters
LTC1555/LTC1556 SIM Power Supply and Level Translator
900kHz Charge Pump, 1mV Ripple
P-P
Step-Up/Step-Down SIM Power Supply and Level Translators
–5V at 150mA from a 5V Input, 5-Lead SOT-23
–5V at 200mA from a 5V Input, MSOP
LT1611
1.4MHz Inverting Mode Switching Regulator
LT1614
Inverting 600kHz Switching Regulator with Low-Battery Detector
Micropower, Regulated 5V Charge Pump with Shutdown in SOT-23
LTC1754-5
I
= 13µA, I
= 50mA (V ≥ 3V), I
= 25mA (V ≥ 2.7V)
OUT IN
CC
OUT
IN
15501lf LT/TP 0300 4K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1996
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
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