It looks like you have to install the whole client software package...bit of bad design really when you only want the ODBC driver, but this is most probably does as SAP want you to use their own BI solution.
The actual ODBC drivers are: HDBODBC (64bit) or HDBODBC32 (32bit) but I can't find anywhere you can download just the driver.
Here's a doc I found: https://kb.informatica.com/h2l/HowTo%20Library/1/0563-ConfigODBCConnToSAPHANA-H2L.pdf
Install the SAP HANA ODBC Driver SAP HANA ODBC drivers are packaged with the SAP HANA client software. Install the client software for the SAP HANA database system. The client software includes the drivers needed to connect to the database. Install the SAP HANA database client, version 1.00.49 or later. Download the SAP HANA client software from the SAP Software Download Center. You must have an account with SAP to download the software. In the United States, you can download the SAP HANA client from the following site: https://hanadeveditionsapicl.hana.ondemand.com/hanadevedition/ Install the SAP HANA client software on the following machines: Servers where the PowerCenter Integration Service or the Data Integration Service run. Machines where Informatica client software is installed