High Voltage Charge Pump Using Standard CMOS Technology Jean-François Richard 1 and Yvon Savaria 2 1 Design and Product Foundry Support department, DALSA Semiconductor Inc., 18 Blvd. de l’Aéroport, Bromont, Québec, Canada, J2L1S7. 2 Electrical Engineering Department, École Polytechnique de Montréal, P.O. Box 6079, Station Centre-ville, Montréal, Québec, Canada, H3C 3A7 Abstract-An integrated high voltage charge pump circuit utilising intrinsic process features is introduced. It can produce +20V to +50V output from a typical 5V input. The reported charge pumps achieved the highest density and highest output voltages of the industry. Measurements show output ripples of 400mV for frequencies around 10MHz and output load of 28pF. The reported integrated high voltage charge pump circuits was implemented on 0.8μm DALSA Semiconductor technology using standard CMOS devices. I. INTRODUCTION Demand for lower supply voltage is getting stronger as portable applications become more popular. Since many processes are not specified for voltages above 5V, requirements for higher power supply voltage and ability to deal with such voltages can become challenging with today’s applications. This is particularly true for automotive parts, telecom interfaces, cellular phones and microelectromechanical systems (MEMS), which often require high supply voltages. The operating supply voltage for high voltage (HV) applications is increasing steadily, ranging from 20V to 300V. Most commercially available and reported charge pumps are limited to maximum output voltages between 12V and 15V. To achieve higher output voltages, bulky, slow and costly solutions based on external discrete components tend to be used. This paper demonstrates that integrated charge pump circuits can be used to boost a standard low input supply voltage to produce +20V to +50V output voltage. These charge pumps offer excellent performance. For instance, the circuits discussed in this paper have some of the highest voltage gain reported [5]. The proposed solution exploits unique process features in order to achieve the highest density and highest output voltages of the industry [1]. Several papers report integrated charge pumps [2], [3] and [4]. Those reported here are adapted from [2] that use a supply voltage of 1.8V. II. SELECTING A CHARGE PUMP ARCHITECTURE The purpose of this section is to justify the selected charge pump structure. Charge pumps have several significant characteristics such as: input voltage range, output voltage and current, internal capacitor values, oscillator frequency, and output voltage ripple. These characteristics are determined by the charge pump structure, and three (3) main classes are considered: the voltage doubler charge pump, the ‘conventional’ Dickson charge pump and the single cascade charge pump. A. The Voltage Doubler Cascade Charge Pump Several different voltage doubler structures have been reported [5] such as the two-phase voltage doubler (TPVD), the Makowski charge pump and the multi-phase voltage doubler (MPVD). Those circuits generally have the best output ripple on the market, with values in the range of few hundred milliVolts or less. High gain structures are derived by cascading a basic circuit stage as shown in fig.1. Each stage produces a constant multiplicative voltage gain. The output voltage of each stage increases until the final voltage of 2xV IN has been reached by using the output voltage of each stage as the input voltage of the next stage. Also, multiphase charge pumps with voltage gain of 2 n requires 2n clock signals to control those switches. For large number of stages, this kind of architecture is not only impractical, since 2 clock signals need to be generated for each new stage, but also the output voltage at each stage must be lower than the breakdown voltages of CMOS drain/substrate junctions and gate oxides. Since we target high number of stages (>10) and higher voltages then the typical 12V gate oxide breakdown, this architecture is not appropriate for our specifications. Figure 1 – Voltage doubler circuit using a two-phase clock generator