CC2640 看门狗复位间隔在4*4封装 在 7*7封装上有较大差异

TI工程师，我用下面的wdtInitFxn()初始化了看门狗，wdtCallback中喂狗语句注释掉了。在4*4封装芯片上运行正常，1s后复位
可是在7*7封装芯片上却要等10s。请问这是什么原因呢？
我已针对4*4芯片选择的4XS的board.h和board.c, 也针对7*7芯片选择了7ID的board.h和board.c

static void wdtInitFxn(void)

{
Watchdog_Params wp;
Watchdog_Handle watchdog;
Watchdog_Params_init(&wp);
wp.callbackFxn = wdtCallback;
wp.debugStallMode = Watchdog_DEBUG_STALL_ON;
wp.resetMode = Watchdog_RESET_ON;

watchdog = Watchdog_open(Board_WATCHDOG, &wp);
// WDT runs always at 48MHz/32, 1500000 stands for 1 second.
Watchdog_setReload(watchdog, 1500000);
}

void wdtCallback(UArg handle)
{
//Watchdog_clear((Watchdog_Handle)handle);
}