Datasheet

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LTC660

100mA CMOS

Voltage Converter

TYPICAL APPLICATION

■

Simple Conversion of 5V to –5V Supply

■

Output Drive: 100mA

■

OUT

: 6.5

Ω

(0.65V Loss at 100mA)

■

BOOST Pin (Pin 1) for Higher Switching Frequency

■

Inverting and Doubling Modes

■

Minimum Open Circuit Voltage Conversion

Efficiency: 99%

■

Typical Power Conversion Efficiency

with a 100mA Load: 88%

■

Easy to Use

The LTC

660 is a monolithic CMOS switched-capacitor

voltage converter. It performs supply voltage conversion

from positive to negative from an input range of 1.5V to

5.5V, resulting in complementary output voltages of

–1.5V to –5.5V. It also performs a doubling at an input

voltage range of 2.5V to 5.5V, resulting in a doubled

output voltage of 5V to 11V. Only two external capacitors

are needed for the charge pump and charge reservoir

functions.

The converter has an internal oscillator that can be

overdriven by an external clock or slowed down when

connected to a capacitor. The oscillator runs at a 10kHz

frequency when unloaded. A higher frequency outside the

audio band can also be obtained if the BOOST pin is tied

to V

The LTC660 contains an internal oscillator, divide-by-two,

voltage level shifter and four power MOSFETs.

■

Conversion of 5V to ±5V Supplies

■

Inexpensive Negative Supplies

■

Data Acquisition Systems

■

High Current Upgrade to LTC1044 or LTC7660

FEATURES

DESCRIPTION

APPLICATIONS

Output Voltage vs

Load Current for V

= 5V

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

–5.0

–4.8

–4.6

–4.4

–4.2

–4.0

660 TA02

100

= 25°C

OUT

= 6.5Ω



, LTC and LT are registered trademarks of Linear Technology Corporation.

Generating –5V from 5V

1

2

3

8

7

6

5



BOOST

CAP



GND

CAP

–

C2

150µF

660 TA01

C1

150µF

–5V

OUTPUT

5V INPUT

LTC660



OSC

LV

OUT



Summary of content (12 pages)

PAGE 1
LTC660 100mA CMOS Voltage Converter U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ Simple Conversion of 5V to – 5V Supply Output Drive: 100mA ROUT: 6.5Ω (0.
PAGE 2
LTC660 W U U W W U W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) ORDER PART NUMBER TOP VIEW Supply Voltage (V +) .................................................. 6V Input Voltage on Pins 1, 6, 7 (Note 2) ............................ – 0.3V < VIN < (V + + 0.3V) Output Short-Circuit Duration to GND (Note 5) ............................................................. 1 sec Power Dissipation.............................................. 500mW Operating Temperature Range ..........
PAGE 3
LTC660 U W TYPICAL PERFORMANCE CHARACTERISTICS (Using Test Circuit in Figure 1) 100 1000 300 TA = 25°C V + = 5V SUPPLY CURRENT (µA) 250 200 150 BOOST = V + 100 BOOST = OPEN TA = 25°C V + = 5V BOOST = OPEN 90 OUTPUT RESISTANCE (Ω) TA = 25°C SUPPLY CURRENT (µA) Output Resistance vs Oscillator Frequency Supply Current vs Oscillator Frequency Supply Current vs Supply Voltage 100 10 50 80 70 60 C1 = C2 = 150µF C1 = C2 = 1500µF 50 40 C1 = C2 = 22µF 30 20 10 0 1.5 2 4 4.5 2.5 3 3.
PAGE 4
LTC660 U W TYPICAL PERFORMANCE CHARACTERISTICS (Using Test Circuit in Figure 1) Output Voltage Drop vs Load Current Output Voltage vs Oscillator Frequency 1.0 TA = 25°C BOOST = V + IL = 1mA 0.8 95 90 –4.5 V + = 2.5V 0.6 0.5 V + = 1.5V 0.4 V + = 3.5V V + = 4.5V 0.3 V + = 5.5V 0.2 IL = 10mA –4.0 IL = 80mA –3.5 –3.0 TA =25°C V+ = 5V BOOST = OPEN 0.1 10 20 30 40 50 60 70 80 90 100 LOAD CURRENT (mA) 1 10 OSCILLATOR FREQUENCY (kHz) LTC660 • TPC10 70 55 50 0.
PAGE 5
LTC660 U U PIN NAME INVERTER DOUBLER 1 BOOST Internal Oscillator Frequency Control Pin. BOOST = Open, fOSC = 10kHz typ; BOOST = V +, fOSC = 80kHz typ; when OSC is driven externally BOOST has no effect.
PAGE 6
LTC660 U U W U APPLICATIONS INFORMATION Theory of Operation V+ (8) I = f • ∆q = f • C1 (V1 – V2) Rewriting in terms of voltage and impedance equivalence, I= V1 − V2 V1 − V2 = 1/ fC1 REQUIV A new variable REQUIV has been defined such that REQUIV = 1/fC1. Thus, the equivalent circuit for the switchedcapacitor network is as shown in Figure 3. Figure 4 shows that the LTC660 has the same switching action as the basic switched-capacitor building block. V2 V1 C1 C2 RL 660 F02 Figure 2.
PAGE 7
LTC660 U U W U APPLICATIONS INFORMATION V+ 7.0I V+ REQUIRED FOR TTL LOGIC NC I + BOOST (1) C1 1 8 2 7 3 LTC660 4 100k OSC INPUT 6 5 –(V +) C2 + OSC (7) SCHMITT TRIGGER Figure 6. External Clocking ∼18pF 7.0I LTC660 • F06 I LV (6) LTC660 • F05 Figure 5. Oscillator By connecting the BOOST pin (Pin 1) to V +, the charge and discharge current is increased and, hence, the frequency is increased by approximately four and a half times.
PAGE 8
LTC660 U TYPICAL APPLICATIONS N Negative Voltage Converter Voltage Doubling Figure 7 shows a typical connection which will provide a negative supply from an available positive supply. This circuit operates over full temperature and power supply ranges without the need of any external diodes. The LV pin (Pin 6) is shown grounded, but for V + ≥ 3V, it may be floated, since LV is internally switched to ground (Pin 3) for V + ≥ 3V. Figure 8 shows the LTC660 operating in the voltage doubling mode.
PAGE 9
LTC660 U TYPICAL APPLICATIONS N VB (9V) 1 2 C1 150µF 3 +VB/2 (4.5V) 7 LTC660 4 6 5 –VB/2 (–4.5V) C2 150µF + OUTPUT COMMON 3V ≤ VB ≤ 11V Additional flexibility of the LTC660 is shown in Figures 11 and 12. Figure 11 shows two LTC660s connected in parallel to provide a lower effective output resistance. If, however, the output resistance is dominated by 1/fC1, increasing the capacitor size (C1) or increasing the frequency will be of more benefit than the paralleling circuit shown.
PAGE 10
LTC660 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.100 ± 0.010 (2.540 ± 0.254) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
PAGE 11
LTC660 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) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.
PAGE 12
LTC660 U TYPICAL APPLICATIONS N Voltage Inverter 1 V+ BOOST 8 VIN 1.5V TO 5.5V 7 CAP+ OSC LTC660 6 3 GND LV 2 + C1 150µF 4 CAP – VOUT 5 VOUT = –VIN C2 150µF + LTC660 • F07 Voltage Doubler 1N5817* 1 VIN 2.5V TO 5.