Overview

The ICL7660 (commonly ICL7660CPA in DIP-8 or TC7660 by Microchip) is a classic CMOS switched-capacitor charge pump voltage converter manufactured by Renesas (originally Intersil). It performs negative voltage inversion, converting a positive input voltage (+1.5 V⋯+10 V+1.5\text{ V} \dots +10\text{ V}) to a corresponding negative output voltage (−1.5 V⋯−10 V-1.5\text{ V} \dots -10\text{ V}) using only two low-cost external capacitors.

Because it requires no inductors or magnetic components, the ICL7660 is widely used in analog audio gear, op-amp circuits, RS-232 level translators, and sensor interfaces to generate negative supply rails (such as −5 V-5\text{ V} from a single +5 V+5\text{ V} supply).

Quick reference

Converter TypeSwitched-Capacitor Charge Pump Voltage Inverter
Package8-Pin DIP (Through-Hole) / SOIC-8
Input Voltage Range (V+V^+)+1.5 V+1.5\text{ V} to +10.0 V+10.0\text{ V} DC (ICL7660A version up to +12 V+12\text{ V})
Output Voltage Range (VOUTV_{OUT})−VIN-V_{IN} (Negative Voltage Inverter mode)
Output Current CapabilityUp to 20 mA20\text{ mA} continuous
Voltage Conversion Efficiency99.9%99.9\% typical (Open circuit)
Power Efficiency98%98\% at IOUT=2mAI_{OUT} = 2\text{mA}
Oscillator Frequency10 kHz10\text{ kHz} internal switching clock (100 kHz100\text{ kHz} with BOOST pin)

Pinout (8-Pin DIP Package)

text
        ┌──────────┐
  NC/BO ─│ 1      8 │─ V+
   CAP+ ─│ 2      7 │─ OSC
    GND ─│ 3      6 │─ LV
   CAP- ─│ 4      5 │─ VOUT
        └──────────┘
PinNameDescription
1BOOST / NCOscillator frequency boost pin (Connect to V+V^+ to increase switching speed)
2CAP+Positive terminal for external charge pump capacitor C1C_1
3GNDGround reference (0 V)
4CAP-Negative terminal for external charge pump capacitor C1C_1
5VOUTInverted negative output voltage pin (−VIN-V_{IN})
6LVLow voltage operation pin (Connect to GND if V+<3.5VV^+ < 3.5\text{V}; open for V+≥3.5VV^+ \ge 3.5\text{V})
7OSCInternal oscillator control input (Connect external cap to GND to slow clock)
8V+Positive supply input (+1.5V to +10.0V DC)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply Voltage RangeV+V^+1.55.010.0VDC operating input
Output ResistanceROUTR_{OUT}—70100Ω\OmegaV+=5V,IOUT=20mAV^+ = 5\text{V}, I_{OUT} = 20\text{mA}
Oscillator FrequencyfOSCf_{OSC}4.010.015.0kHzV+=5VV^+ = 5\text{V}, Pin 1 open
Voltage Conversion EfficiencyEVE_V99.099.9—%Open circuit
Supply CurrentISI_S—80170μA\mu\text{A}V+=5VV^+ = 5\text{V}, IOUT=0I_{OUT} = 0

Typical Application Circuit (Positive-to-Negative Voltage Inverter)

text
       +5V Power Input
          │
       [Pin 8: V+]
        ICL7660 ─── [Pin 2: CAP+] ─── [ 10µF Capacitor C1 ] ─── [Pin 4: CAP-]
          │
       [Pin 3: GND] ─── GND
          │
       [Pin 5: VOUT] ──┬─── -5V Inverted Output
                       │
                    [ 10µF Capacitor C2 ]
                       │
                      GND

Common mistakes

  • Leaving the LV pin floating at low operating voltages: When operating below +3.5 V+3.5\text{ V} input, Pin 6 (LV) MUST be connected directly to GND. Leaving LV open at low supply voltages halts switching.
  • Exceeding the 10V input limit on standard ICL7660: Standard ICL7660 absolute maximum rating is +10.5 V+10.5\text{ V}. Connecting +12 V+12\text{ V} or higher destroys the internal MOS switches (use the ICL7660A or MAX1044 for inputs up to +12 V+12\text{ V}).

Notes

  • Op-Amp Dual Supply Generation: The ICL7660 is the classic choice for deriving a −5 V-5\text{ V} rail from a single +5 V+5\text{ V} USB or 5V logic rail to power dual-rail analog op-amps like the TL072 or LM358.

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