You could use the ifsym package (but it only provides bitmap fonts) or draw yourself the symbol. Equation (1) below shows the hand-made symbol, equation (2) uses ifsym. If you go for method (1), loading ifsym is unnecessary, but pict2e is.
One should note that the symbols provided by ifsym are for text, so if used in math they have to be surrounded by \text.
\documentclass{article}
\usepackage{amsmath}
\usepackage{pict2e}
\usepackage[electronic]{ifsym}
\DeclareRobustCommand{\pulse}{%
\text{%
\settoheight{\unitlength}{T}%
\begin{picture}(2.2,1)
\roundcap
\polyline(0.1,0)(0.6,0)(0.6,1)(1.6,1)(1.6,0)(2.1,0)
\end{picture}%
}%
}
\begin{document}
\begin{equation}
E_{\mathrm{dyn}} =
V_{\mathrm{DD}}\int\limits_{\pulse} I_{\mathrm{tot}}(t)\,dt
- P_{\mathrm{stat}}\cdot T
\end{equation}
\begin{equation}
E_{\mathrm{dyn}} =
V_{\mathrm{DD}}\int\limits_{\text{\PulseHigh}} I_{\mathrm{tot}}(t)\,dt
- P_{\mathrm{stat}}\cdot T
\end{equation}
\end{document}

ifsymprovides\PulseHigh– egreg Apr 28 '17 at 09:55\int I_{tot}(t) p(t) dt, wherep(t)is your pulse profile. – bers Apr 28 '17 at 10:26