There are two different non X-ray background (NXB) models of HXD-PIN;
As noted in the ABC guide and Suzaku first step guid (Japanese), one should understand the cross calibration issue between the XIS and the HXD-PIN described in the Suzaku Documents page , when analyzing the data.
As of 2008.08.29, you shall refer to
"Recent update of the XRT response: III. Effective Area" (suzakumemo-2008-06) .
On the original rev 2.x XIS calibration, you shall refer to
"Relative normalization of XIS0-3 and PIN in revision 2 data" (suzakumemo-2007-11) .